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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	AMICUS THERAPEUTICS INC
Entity Central Index Key	0001178879
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 888,863,221
Entity Common Stock, Shares Outstanding		186,891,419
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 49,060	$ 187,026
Investments in marketable securities	309,502	143,325
Accounts receivable	9,464	1,304
Inventories	4,623	3,416
Prepaid expenses and other current assets	19,316	4,993
Total current assets	391,965	340,064
Property and equipment, less accumulated depreciation of $12,515 and $12,495 at December 31, 2017 and 2016, respectively	9,062	9,816
In-process research & development	23,000	486,700
Goodwill	197,797	197,797
Other non-current assets	5,200	2,468
Total Assets	627,024	1,036,845
Current liabilities:
Accounts payable, accrued expenses, and other current liabilities	53,890	41,008
Deferred reimbursements, current portion	7,750	13,850
Contingent consideration payable, current portion	8,400	56,101
Total current liabilities	70,040	110,959
Deferred reimbursements	14,156	21,906
Convertible notes	164,167	154,464
Contingent consideration payable	17,000	213,621
Deferred income taxes	6,465	173,771
Other non-current liability	2,346	1,973
Commitments and contingencies
Stockholders' equity:
Common stock, $.01 par value, 250,000,000 shares authorized, 166,989,790 shares issued and outstanding at December 31, 2017 Common stock, $.01 par value, 250,000,000 shares authorized, 142,691,986 shares issued and outstanding at December 31, 2016	1,721	1,480
Additional paid-in capital	1,400,758	1,120,156
Accumulated other comprehensive loss:
Foreign currency translation adjustment	(1,659)	1,945
Unrealized gain/(loss) on available-for securities	(436)	102
Warrants	16,076	16,076
Accumulated deficit	(1,063,610)	(779,608)
Total stockholders' equity	352,850	360,151
Total Liabilities and Stockholders' Equity	$ 627,024	$ 1,036,845

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Accumulated depreciation of property and equipment (in dollars)	$ 12,515	$ 12,495
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	166,989,790	142,691,986
Common stock, shares outstanding	166,989,790	142,691,986

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Net Product Sales	$ 36,930	$ 4,958
Total revenue	36,930	4,958
Cost of goods sold	6,236	833
Gross Profit	30,694	4,125
Operating Expenses:
Research and development	149,310	104,793	$ 76,943
Selling, general and administrative	88,671	71,151	47,269
Changes in fair value of contingent consideration payable	(234,322)	6,760	4,377
Loss on impairment of assets	465,427
Restructuring charges		69	15
Depreciation	3,593	3,242	1,833
Total operating expenses	472,679	186,015	130,437
Loss from operations	(441,985)	(181,890)	(130,437)
Other income (expenses):
Interest income	4,096	1,602	929
Interest expense	(17,240)	(5,398)	(1,578)
Loss on extinguishment of debt		(13,302)	(952)
Other income (expense)	6,008	(4,793)	(80)
Loss before income tax benefit	(449,121)	(203,781)	(132,118)
Income tax benefit	165,119	3,739
Net loss attributable to common stockholders	$ (284,002)	$ (200,042)	$ (132,118)
Net loss attributable to common stockholders per common share - basic and diluted	$ (1.85)	$ (1.49)	$ (1.20)
Weighted-average common shares outstanding - basic and diluted	153,355,144	134,401,588	109,923,815

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Loss
Net loss	$ (284,002)	$ (200,042)	$ (132,118)
Other comprehensive gain/ (loss):
Foreign currency translation adjustment	(3,604)	1,945
Unrealized (loss)/gain on available-for-sale securities	(538)	217	17
Other comprehensive (loss)/ income	(4,142)	2,162	17
Comprehensive loss	$ (288,144)	$ (197,880)	$ (132,101)

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Scioderm Common Stock	Scioderm Additional Paid-In Capital	Scioderm	Callidus Common Stock	MiaMed Common Stock	MiaMed Additional Paid-In Capital	MiaMed	Common Stock	Additional Paid-In Capital	Warrants	Other Comprehensive Gain/ (Loss)	Accumulated Deficit	Total
Balance at Dec. 31, 2014								$ 1,015	$ 568,743		$ (132)	$ (447,448)	$ 122,178
Balance (in shares) at Dec. 31, 2014								95,556,277
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net								$ 21	11,165				11,186
Stock issued from exercise of stock options, net (in shares)								2,070,300
Stock issued from equity financing								$ 195	242,847				243,042
Stock issued from equity financing (in shares)								19,528,302
Stock issued for acquisition	$ 59	$ 82,787	$ 82,846
Stock issued for acquisition (in shares)	5,921,771			25,762
Stock issued from exercise of warrants								$ 16	3,984				4,000
Stock issued from exercise of warrants (in shares)								1,600,000
Restricted stock vesting									(2,044)				(2,044)
Restricted stock vesting (in shares)								324,622
Warrants issued in debt financing										$ 8,755			8,755
Stock-based compensation									9,972				9,972
Unrealized holding gain/(loss) on available-for-sale securities											17		17
Net loss												(132,118)	(132,118)
Balance at Dec. 31, 2015								$ 1,306	917,454	8,755	(115)	(579,566)	347,834
Balance (in shares) at Dec. 31, 2015								125,027,034
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net								$ 7	3,029				3,036
Stock issued from exercise of stock options, net (in shares)								723,102
Stock issued for acquisition					$ 8	$ 4,599	$ 4,607
Stock issued for acquisition (in shares)					825,603
Stock issued from ATM transactions								$ 150	96,918				97,068
Stock issued from ATM transactions (in shares)								14,989,027
Restricted stock vesting									(1,282)				(1,282)
Restricted stock vesting (in shares)								268,425
Stock issued for contingent consideration								$ 9	6,106				6,115
Stock issued for contingent consideration (in shares)								858,795
Receivable from investor									932				932
Warrants issued in debt financing										7,321			7,321
Equity component of the Convertible Notes issuance, net of issuance costs of $2,709									88,346				88,346
Premium paid for Capped Call Confirmations									(13,450)				(13,450)
Stock-based compensation									17,504				17,504
Unrealized holding gain/(loss) on available-for-sale securities											217		217
Foreign currency translation adjustment											1,945		1,945
Net loss												(200,042)	(200,042)
Balance at Dec. 31, 2016								$ 1,480	1,120,156	16,076	2,047	(779,608)	$ 360,151
Balance (in shares) at Dec. 31, 2016								142,691,986					142,691,986
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net								$ 29	16,272				$ 16,301
Stock issued from exercise of stock options, net (in shares)								2,878,681
Stock issued from equity financing								$ 212	242,825				243,037
Stock issued from equity financing (in shares)								21,122,449
Restricted stock vesting									(1,596)				(1,596)
Restricted stock vesting (in shares)								296,674
Stock-based compensation									23,101				23,101
Unrealized holding gain/(loss) on available-for-sale securities											(538)		(538)
Foreign currency translation adjustment											(3,604)		(3,604)
Net loss												(284,002)	(284,002)
Balance at Dec. 31, 2017								$ 1,721	$ 1,400,758	$ 16,076	$ (2,095)	$ (1,063,610)	$ 352,850
Balance (in shares) at Dec. 31, 2017								166,989,790					166,989,790

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	Dec. 31, 2016 USD ($)
Consolidated Statements of Changes in Stockholders' Equity
Convertible notes issuance costs	$ 2,709

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (284,002)	$ (200,042)	$ (132,118)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash interest expense	9,703	2,689	492
Depreciation	3,593	3,242	1,833
Stock-based compensation	23,101	17,504	9,972
Restructuring charges		69	15
Change in fair value of derivative liability	(265)	265
Non-cash changes in the fair value of contingent consideration payable	(234,322)	6,760	4,377
Charges to research expense for stock issued in asset acquisition		4,607
Loss on extinguishment of debt		13,302	952
Foreign currency remeasurement (gain) loss	(5,620)	3,660
Non-cash deferred taxes and other tax benefits	(167,305)	(3,742)
(Gain) Loss on disposal of assets	(8)	17
Impairment of IPR&D	465,427
Changes in operating assets and liabilities:
Accounts receivable	(7,725)	(1,419)
Inventories	(897)	(3,651)
Prepaid expenses and other current assets	(15,329)	(394)	308
Other non-current assets	(2,519)	(1,357)	(666)
Account payable and accrued expenses	12,563	7,131	15,467
Non-current liabilities	720	825	93
Deferred reimbursements	(12,600)		(864)
Net cash used in operating activities	(215,485)	(150,534)	(100,139)
Investing activities
Sale and redemption of marketable securities	323,753	221,374	290,129
Purchases of marketable securities	(490,468)	(219,932)	(289,595)
Acquisitions, net of cash acquired			(141,060)
Purchases of property and equipment	(4,526)	(5,951)	(4,817)
Net cash used in investing activities	(171,241)	(4,509)	(145,343)
Financing activities
Proceeds from issuance of common stock and warrants, net of issuance costs	243,037	97,068	243,042
Payments of secured loan agreement		(80,000)	(15,291)
Payment of capital leases	(308)	(193)
Purchase of vested restricted stock units	(1,596)	(1,282)	(2,044)
Proceeds from exercise of stock options	16,301	3,036	11,186
Proceeds from exercise of warrants			4,000
Payment of contingent consideration	(10,000)	(5,000)
Proceeds from issuance of convertible senior notes, net of issuance costs		242,536
Premiums paid for Capped Call Confirmations		(13,450)
Proceeds from secured loan agreement		30,000	50,000
Net cash provided by financing activities	247,434	272,715	290,893
Effect of exchange rate changes on cash and cash equivalents	1,326	(131)
Net (decrease)/increase in cash and cash equivalents	(137,966)	117,541	45,411
Cash and cash equivalents at beginning of year/ period	187,026	69,485	24,074
Cash and cash equivalents at end of year/period	49,060	187,026	69,485
Supplemental disclosures of cash flow information
Cash paid during the period for interest	$ 7,424	2,990	$ 605
Contingent consideration paid in shares		6,115
Capital expenditures funded by capital lease borrowings		$ 944

Description of Business	12 Months Ended
Description of Business	Dec. 31, 2017
Description of Business
Description of Business	1. Description of Business Corporate Information, Status of Operations, and Management Plans Amicus Therapeutics, Inc. (the "Company") is a global patient-centric biotechnology company engaged in the discovery, development and commercialization of a diverse set of novel high-quality treatments for patients living with rare metabolic diseases. The cornerstone of the Amicus portfolio is migalastat HCl, an oral precision medicine for people living with Fabry disease who have amenable genetic mutations. Migalastat is currently approved under the trade name GALAFOLD in the European Union, with additional approvals granted and pending in several geographies. For Fabry patients with non-amenable genetic mutations, a novel proprietary enzyme replacement therapy ("ERT") co-formulated with migalastat HCl is currently in late preclinical development. The future value driver of the Amicus pipeline is ATB200/AT2221, a novel, late-stage, potential best-in-class treatment paradigm for Pompe disease. ATB200/AT2221 leverages our Chaperone-Advanced Replacement Therapy ("CHART®") platform technology to develop novel ERT products for Pompe disease, Fabry disease, and potentially other lysosomal storage disorders ("LSDs"). The Company is also investigating preclinical and discovery programs in other rare diseases including cyclin-dependent kinase-like 5 ("CDKL5") deficiency. The Company believes that its platform technologies and its product pipeline uniquely position them and drive their commitment to advancing and expanding a robust pipeline of cutting-edge, first- or best-in-class medicines for rare metabolic diseases. The Company was previously developing SD-101 in late-stage development as a potential first-to-market therapy for the chronic, rare connective tissue disorder Epidermolysis Bullosa ("EB"). On September 13, 2017, the Company reported that top-line data from the randomized, double-blind, placebo-controlled Phase 3 clinical study ("ESSENCE" or "SD-005") to assess the efficacy and safety of the novel topical wound-healing agent SD-101 did not meet the primary endpoints or secondary endpoints in participants with EB. The Company plans to further analyze and share the Phase 3 ESSENCE results with key stakeholders in the EB community including physicians, patient organizations and regulators. In the interim, in consultation with their physicians, participants in the ongoing extension studies (SD-004 and -006) will have the opportunity to continue being treated with SD-101. Based on the top-line data, the Company has no current plans to invest in any additional clinical studies or commercial preparation activities for SD-101. This event led the Company to assess the carrying amount of the program's tangible and intangible assets against their respective fair values. Based on the assessment, the Company recognized a loss on impairment of intangible assets in the amount of $463.7 million and $1.7 million in fixed assets recorded within Loss on Impairment of Assets within the Consolidated Statements of Operations. Since the study did not meet the primary and secondary endpoints, the Company has concluded that they will not make the potential milestone payments indicated in the Asset Purchase Agreement to the former Scioderm holders. Accordingly, the Company recognized a gain of $254.7 million in Changes in Fair Value of Contingent Consideration Payable in the third quarter of 2017, in order to decrease the liability to zero. The Company also recognized $0.4 million in selling, general and administrative costs and $8.1 million in research and development expenses related to the wind-down of operations for the Phase 3 ESSENCE study and ongoing extension studies SD-004 and SD-006, as well as income tax benefit of $164.7 million due to the reduction of the deferred tax liability related to Scioderm IPR&D, in the Consolidated Statements of Operations in the third quarter of 2017. See "— Note 4. Goodwill and IPR&D" for more details. On February 15, 2018, the Company announced the pricing of an underwritten offering of 19,354,839 shares of its common stock at $15.50 per shares, resulting in gross proceeds of $300.0 million, before deducting underwriting discounts and commissions and offering expenses payable by the Company. The offering closed on February 21, 2018 and the Company received net proceeds of $282.0 million from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by the Company. J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC were acting as joint lead book-running managers, Cowen and Leerink Partners were acting as co-book-running managers, and BofA Merrill Lynch was acting as lead co-manager for the offering. The Company expects to use the net proceeds of the offering for investment in the U.S. and international commercial infrastructure for migalastat HCl, investment in manufacturing capabilities for ATB200, the continued clinical development of its product candidates, research and development expenditures, clinical and pre-clinical trial expenditures, commercialization expenditures and for other general corporate purposes. In July 2017, the Company entered into an underwriting agreement ("the Underwriting Agreement") with J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC, as representatives of the several underwriters set forth on Schedule 1 thereto, relating to an underwritten public offering of the Company's common stock (the "Offering"). Under the terms of the Underwriting Agreement, the Company issued and sold 21,122,449 shares at a price to the public of $12.25 per share, resulting in gross proceeds of $258.8 million, before deducting underwriting discounts and commissions and offering expenses payable by the Company. The Offering closed on July 18, 2017 and the Company received net proceeds from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by the Company of $243.0 million. See "— Note 9. Equity" for more details. In December 2016, the Company issued $250 million aggregate principal amount of 3.00% unsecured Convertible Senior Notes due 2023 (the "Convertible Notes"), in a private offering to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the "Securities Act"). Interest is payable semiannually on June 15 and December 15 of each year, beginning on June 15, 2017. The Notes will mature on December 15, 2023, unless earlier repurchased, redeemed, or converted in accordance with their terms. The Notes are convertible at the option of the holders, under certain circumstances and during certain periods, into cash, shares of the Company's common stock, par value $0.01 per share ("Common Stock"), or a combination thereof. The net proceeds from the issuance of the Convertible Note offering were $243.0 million, after deducting fees and estimated expenses payable by the Company. In addition, the Company used approximately $13.5 million of the net proceeds from the issuance of the Convertible Notes to pay the cost of the capped call transactions ("Capped Call Confirmations") that the Company entered into in connection with the issuance of the Convertible Notes. For additional information, see "— Note 11. Debt Instruments and Related Party Transactions." In July 2016, the Company expanded its biologics pipeline with a new preclinical program for CDKL5 deficiency, a rare and devastating genetic neurological disease for which there is no currently approved treatment. The Company has obtained the rights and related intellectual property to a preclinical CDKL5 program through its acquisition of MiaMed, Inc. ("MiaMed"). The aggregate value of the deal was approximately $89.5 million, which included an upfront payment of $6.5 million and Company stock, cash and potential milestones of up to $83.0 million. For additional information, see "— Note 3. Acquisitions". Beginning in April 2016 and through July 2016, the Company sold 15.0 million shares of Common Stock under an at-the-market ("ATM") equity program with Cowen and Company, LLC ("Cowen") acting as sales agent. Cowen was compensated at a fixed commission rate up to 3.0%. The ATM sales agreement resulted in net proceeds of $97.1 million, after Cowen's commission of $2.7 million and other expenses of $0.2 million. The Company has completed all sales under the ATM equity program. The Company had an accumulated deficit of approximately $1.1 billion at December 31, 2017 and anticipates incurring losses through the fiscal year ending December 31, 2018 and beyond. The Company has been able to fund its operating losses to date through stock offering, debt issuances, and payments from partners during the terms of the collaboration agreements and other financing arrangements. The current cash position, including proceeds from the recent equity offering and expected Galafold revenues, is sufficient to fund ongoing Fabry and Pompe program operations into at least 2021. Potential future business development collaborations, pipeline expansion, and investment in biologics manufacturing capabilities could impact the Company's future capital requirements.

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") and include all adjustments necessary for the fair presentation of the Company's financial position for the periods presented. Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany accounts and transactions are eliminated in consolidation. Foreign Currency Transactions The functional currency for most of the Company's foreign subsidiaries is their local currency. For non-U.S. subsidiaries that transact in a functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of the Company's foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of equity. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. Cash, Money Market Funds, and Marketable Securities The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of acquisition, to be cash equivalents. Marketable securities consist of fixed income investments with a maturity of greater than three months and other highly liquid investments that can be readily purchased or sold using established markets. These investments are classified as available-for-sale and are reported at fair value on the Company's balance sheet. Unrealized holding gains and losses are reported within comprehensive income/ (loss) in the statements of comprehensive loss. Fair value is based on available market information including quoted market prices, broker or dealer quotations or other observable inputs. See "— Note 5. Cash, Money Market Funds and Marketable Securities", for a summary of available-for-sale securities as of December 31, 2017 and 2016. Concentration of Credit Risk The Company's financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and marketable securities. The Company maintains its cash and cash equivalents in bank accounts, which, at times, exceed federally insured limits. The Company invests its marketable securities in high-quality commercial financial instruments. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on cash and cash equivalents or its marketable securities. The Company is subject to credit risk from its accounts receivable related to its product sales of GALAFOLD. The Company's accounts receivable at December 31, 2017 have arisen from product sales in the EU. The Company will periodically assess the financial strength of its customers to establish allowances for anticipated losses, if any. For accounts receivable that have arisen from named patient sales, the payment terms are predetermined and the Company evaluates the creditworthiness of each customer on a regular basis. To date, the Company has not incurred any credit losses. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated over the estimated useful lives of the respective assets, which range from three to five years, or the lesser of the related initial term of the lease or useful life for leasehold improvements. The initial cost of property and equipment consists of its purchase price and any directly attributable costs of bringing the asset to its working condition and location for its intended use. Expenditures incurred after the fixed assets have been put into operation, such as repairs and maintenance, are charged to income in the period in which the costs are incurred. Major replacements, improvements and additions are capitalized in accordance with Company policy. Revenue Recognition The Company recognizes revenue when amounts are realized or realizable and earned, which is typically upon receipt by the customer. Revenue is considered realizable and earned when persuasive evidence an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collection of the amounts due are reasonably assured and the Company has no further performance obligations. Net Product Sales The Company's net product sales consist solely of sales of GALAFOLD for the treatment of Fabry disease in the EU. The Company has recorded revenue on sales where GALAFOLD is available either on a commercial basis or through a reimbursed early access program. Orders for GALAFOLD are generally received from pharmacies and the ultimate payor is typically a government authority. The Company records revenue net of estimated third party discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. These allowances are adjusted to reflect known changes in factors and may impact such allowances in the quarter those changes are known. Inventories and Cost of Goods Sold Prior to regulatory approval of GALAFOLD, the Company expensed all manufacturing costs related to GALAFOLD as research and development expense. Upon regulatory approval, the Company began capitalizing costs related to the purchase and manufacture of GALAFOLD. Inventories are stated at the lower of cost and net realizable value, determined by the first-in, first-out method. Inventories are reviewed periodically to identify slow-moving or obsolete inventory based on projected sales activity as well as product shelf-life. In evaluating the recoverability of inventories produced, the probability that revenue will be obtained from the future sale of the related inventory is considered and inventory value is written down for inventory quantities in excess of expected requirements. Expired inventory is disposed of and the related costs are recognized as cost of product sales in the consolidated statements of operations. Cost of goods sold includes the cost of inventory sold, manufacturing and supply chain costs, product shipping and handling costs, provisions for excess and obsolete inventory, as well as royalties payable. A portion of the inventory available for sale was expensed as research and development costs prior to regulatory approval and as such the cost of goods sold and related gross margins are not necessarily indicative of future cost of goods sold and gross margin. Fair Value Measurements The Company records certain asset and liability balances under the fair value measurements as defined by the FASB guidance. Current FASB fair value guidance emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, current FASB guidance establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity's own assumptions that market participants assumptions would use in pricing assets or liabilities (unobservable inputs classified within Level 3 of the hierarchy). Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at measurement date. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity's own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company's assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. Contingent Liabilities On an ongoing basis, the Company may be involved in various claims, and legal proceedings. On a quarterly basis, the Company reviews the status of each significant matter and assesses its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, the Company will accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals will be based on the Company's best estimates based on available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims, the Company may reassess the potential liability related to these matters and may revise these estimates, which could result in material adverse adjustments to the Company's operating results. Research and Development Costs Research and development costs are expensed as incurred. Research and development expense consists primarily of costs related to personnel, including salaries and other personnel related expenses, consulting fees and the cost of facilities and support services used in drug development. Assets acquired that are used for research and development and have no future alternative use are expensed as in-process research and development. Interest Income and Interest Expense Interest income consists of interest earned on the Company's cash and cash equivalents and marketable securities. Interest expense consists of interest incurred on debt and capital leases. Income Taxes The Company accounts for income taxes under the liability method. Under this method deferred income tax liabilities and assets are determined based on the difference between the financial statement carrying amounts and tax basis of assets and liabilities and for operating losses and tax credit carry forwards, using enacted tax rates in effect in the years in which the differences are expected to reverse. A valuation allowance is recorded if it is "more likely than not" that a portion or all of a deferred tax asset will not be realized. Other Comprehensive Income/ (Loss) Components of other comprehensive income/ (loss) include unrealized gains and losses on available-for-sale securities and gain/ (loss) on foreign currency transactions, and are included in the statements of comprehensive loss. Leases In the ordinary course of business, the Company enters into lease agreements for office space as well as leases for certain property and equipment. The leases have varying terms and expirations and have provisions to extend or renew the lease agreement, among other terms and conditions, as negotiated. Once the agreement is executed, the lease is assessed to determine whether the lease qualifies as a capital or operating lease. When a non-cancelable operating lease includes any fixed escalation clauses and lease incentives for rent holidays or build-out contributions, rent expense is recognized on a straight-line basis over the initial term of the lease. The excess between the average rental amount charged to expense and amounts payable under the lease is recorded in accrued expenses. Nonqualified Cash Deferral Plan The Company's Cash Deferral Plan (the "Deferral Plan"), provides certain key employees and members of the Board of Directors as selected by the Compensation Committee of the Board of Directors of the Company (the "Compensation Committee"), with an opportunity to defer the receipt of such participant's base salary, bonus and director's fees, as applicable. The Deferral Plan is intended to be a nonqualified deferred compensation plan that complies with the provisions of Section 409A of the Internal Revenue Code (the "Code"). All of the investments held in the Deferral Plan are classified as investments held-to-maturity and recorded at fair value with changes in the investments' fair value recognized as earnings in the period they occur. The corresponding liability for the Deferral Plan is included in other non-current liability in the consolidated balance sheets. Equity-based Compensation At December 31, 2017, the Company had three equity-based employee compensation plans, which are described more fully in "— Note 9. Stockholders' Equity." The Company applies the fair value method of measuring equity-based compensation, which requires a public entity to measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. Loss per Common Share The Company calculates net loss per share as a measurement of the Company's performance while giving effect to all dilutive potential common shares that were outstanding during the reporting period. The Company had a net loss for all periods presented; accordingly, the inclusion of common stock options, unvested RSUs and warrants would be anti-dilutive. Therefore, the weighted average shares used to calculate both basic and diluted earnings per share are the same. See "— Note 17. Earnings per Share" for further discussion on net loss per share. Segment Information The Company currently operates in one business segment focused on the discovery, development and commercialization of advanced therapies to treat a range of devastating rare and orphan diseases. The Company is not organized by market and is managed and operated as one business. A single management team reports to the chief operating decision maker who comprehensively manages the entire business. The Company does not operate any separate lines of business or separate business entities with respect to its products. Accordingly, the Company does not accumulate discrete financial information with respect to separate service lines and does not have separately reportable segments. Business Combinations The Company assigns fair value to the tangible and intangible assets acquired and liabilities assumed based upon their estimated fair values on the acquisition date from acquired businesses. The purchase price allocation process requires management to make significant estimates and assumptions, especially at the acquisition date with respect to intangible assets and in-process research and development ("IPR&D"). In connection with the purchase price allocations for acquisitions, the Company estimates the fair value of contingent payments utilizing a probability-based income approach inclusive of an estimated discount rate. Contingent Consideration Payable The Company determines the fair value of contingent acquisition consideration payable on the acquisition date using a probability-based income approach utilizing an appropriate discount rate. Contingent acquisition consideration payable is shown as a non-current liability on the Company's consolidated balance sheets. The fair value of the contingent consideration payable will be determined each period end and the resulting change will be recorded on the consolidated statements of operations. Intangible Assets and Goodwill The Company records goodwill in a business combination when the total consideration exceeds the fair value of the net tangible and identifiable intangible assets acquired. Purchased IPR&D is accounted for as an indefinite lived intangible asset until the underlying project is completed, at which point the intangible asset will be accounted for as a definite lived intangible asset, or abandoned, at which point the intangible asset will be written off or partially impaired. Goodwill and indefinite lived intangible assets are assessed annually for impairment and whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined that the full carrying amount of an asset is not recoverable, an impairment loss is recorded in the amount by which the carrying amount of the asset exceeds its fair value. Recent Accounting Pronouncements In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendments in this Update better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. To meet that objective, the amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in this Update also make certain targeted improvements to simplify the application of hedge accounting guidance and ease the administrative burden of hedge documentation requirements and assessing hedge effectiveness. For public business entities, the amendment is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption, including adoption in an interim period, is permitted. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception. Part I of this Update addresses the complexity of accounting for certain financial instruments with down round features. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced on the basis of the pricing of future equity offerings. When determining whether certain financial instruments should be classified as liabilities or equity instruments, a down round feature no longer precludes equity classification when assessing whether the instrument is indexed to an entity's own stock. Part II of this Update addresses the difficulty of navigating Topic 480, Distinguishing Liabilities from Equity, because of the existence of extensive pending content in the FASB Accounting Standards Codification®. For public business entities, the amendments in Part I of this Update are effective for fiscal years, and years, beginning after December 15, 2018. Early adoption is permitted for all entities, including adoption in an interim period. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting. The amendments provide guidance on determining which changes to the terms and conditions of share-based payment awards require an entity to apply modification accounting under Topic 718 Compensation — Stock Compensation. An entity should account for the effects of a modification unless all the following are met: 1. The fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the modified award is the same as the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the original award immediately before the original award is modified. If the modification does not affect any of the inputs to the valuation technique that the entity uses to value the award, the entity is not required to estimate the value immediately before and after the modification. 2. The vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified. 3. The classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The ASU is effective for all entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, including adoption in any interim period. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables — Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. The amendments shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The ASU is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. For other entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles — Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. To simplify the subsequent measurement of goodwill, ASU 2017-04 eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. ASU 2017-04 also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 should be applied on a prospective basis. The nature of and reason for the change in accounting principle should be disclosed upon transition. A public business entity that is a U.S. SEC filer should adopt ASU 2017-04 for its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. This Accounting Standards Update clarifies the definition of a business. The amendments affect all companies and other reporting organizations that must determine whether they have acquired or sold a business. The amendments in this Update are effective for public companies for annual periods beginning after December 15, 2017, including interim periods within those periods. Early adoption is permitted under certain circumstances. The amendments should be applied prospectively as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. This Accounting Standards Update requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The amendments eliminate the exception for an intra-entity transfer of an asset other than inventory. The amendments in this Update are effective for public business entities for annual periods beginning after December 15, 2017, including interim reporting periods within those annual reporting periods. Early adoption is permitted for all entities in the first interim period if an entity issues interim financial statements. The Company is currently assessing the impact that this standard will have on its consolidated financial statements and plans to adopt this ASU in the first quarter of 2018 using a modified retrospective approach with any adjustment, if any, to be recorded in retained earnings as January 1, 2018. The Company is completing the assessment of the impact, if any, of the adoption of this standard. In March 2016, the FASB issued ASU 2016-09, Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The amendments are intended to improve the accounting for employee share-based payments and affect all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment award transactions are simplified, including: (a) income tax consequences; (b) classification of awards as either equity or liabilities; and (c) classification on the statement of cash flows. For public companies, the amendments are effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted for any organization in any interim or annual period. The Company adopted ASU 2016-09 on January 1, 2017. The adoption resulted in an increase to the Company's NOL and valuation allowance by $4.0 million, however there was no impact on Retained earnings and the classification of excess tax benefits on the statement of cash flows for prior periods have not been adjusted. In connection with the adoption of ASU 2016-9, the Company has decided to continue its current policy and estimate forfeitures and adjust the estimate when it is likely to change. This election will have no impact on the Company's consolidated financial statements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This update requires the recognition of lease assets and lease liabilities on the balance sheet for all lease obligations and disclosing key information about leasing arrangements. This update requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous generally accepted accounting principles. This update will be effective for the Company for all annual and interim periods beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted for all public business entities and all nonpublic business entities upon issuance. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, "Financial Instruments — Overall: Recognition and Measurement of Financial Assets and Financial Liabilities" (ASU 2016-01). ASU 2016-01 changes accounting for equity investments, financial liabilities under the fair value option, and presentation and disclosure requirements for financial instruments. ASU 2016-01 does not apply to equity investments in consolidated subsidiaries or those accounted for under the equity method of accounting. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. Equity investments with readily determinable fair values will be measured at fair value with changes in fair value recognized in net income. Companies have the option to either measure equity investments without readily determinable fair values at fair value or at cost adjusted for changes in observable prices minus impairment. Companies that elect the fair value option for financial liabilities must recognize changes in fair value related to instrument-specific credit risk in other comprehensive income. Companies must assess valuation allowances for deferred tax assets related to available-for-sale debt securities in combination with their other deferred tax assets. ASU 2016-01 will be effective beginning in the first quarter of 2018. We will adopt this ASU in the first quarter of 2018. We expect the implementation of this standard to have no impact on our Consolidated Financial Statements and related disclosures, as the Company does not have equity investments and liabilities with credit risk and the guidance relating to deferred tax assets is currently in place at Amicus even prior to the adoption of the ASU. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes. ASU 2015-17 requiring companies to classify all deferred tax assets and liabilities as noncurrent on the balance sheet instead of separating deferred taxes into current and noncurrent amounts. For public business entities, the guidance is effective for financial statements issued for annual periods beginning after 15 December 2016, and interim periods within those annual periods. The Company adopted this guidance as of January 1, 2017 and the adoption did not have a material impact on its consolidated financial statements. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which requires an entity to measure in scope inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendments apply to inventory that is measured using first-in, first-out (FIFO) or average cost. The ASU is effective for public business entities for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. A reporting entity should apply the amendments prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company adopted this guidance as of January 1, 2017 and the adoption did not have any impact on its consolidated financial statements. In May 2014, FASB issued ASU 2014-09, Revenue from Contracts with Customers which along with amendments issued in 2015 and 2016, will replace substantially all current US GAAP guidance on this topic and eliminate industry-specific guidance. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance permits two methods of adoption: full retrospective method (retrospective application to each prior reporting period presented) or modified retrospective method (retrospective application with the cumulative effect of initially applying the guidance recognized at the date of initial application and providing certain additional disclosures). The Company has elected to adopt the new standard using the modified retrospective approach. ASU 2014-09 is effective for the Company during the first quarter of 2018. The Company's implementation plan included a phased project plan, an understanding of the new standard and its requirements, assessment of the Company's revenue streams and specific contracts in the streams. Additionally, the Company continues to monitor modifications, clarifications and interpretations issued by the FASB that may impact its assessment. While the Company performed a detailed review of representative contracts and assessed the potential impacts the standard may have on previously reported revenues and future revenues, the Company is finalizing its assessment of the adoption of the new standard. Based on the adoption of the ASU 2014-09, the Company identified two revenue streams: sales to distributors and pharmacies. The timing of revenue recognition and treatment of contract costs remains unchanged under the new standard. As such, the Company does not expect the adoption of ASU 2014-09 to have a material impact on its consolidated financial statements. The Company does expect the adoption of the new standard to impact its financial reporting disclosures and internal controls over financial reporting. The Company has developed implementation controls that allow the Company to properly and timely adopt the new revenue accounting standard on its effective date.

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2017
Acquisitions
Acquisitions	3. Acquisitions Acquisition of MiaMed, Inc. In July 2016, the Company entered into an Agreement and Plan of Merger (the "MiaMed Agreement") with MiaMed, Inc., ("MiaMed"). MiaMed is a pre-clinical biotechnology company focused on developing protein replacement therapy for CDKL5 and related diseases. Under the terms of the MiaMed Agreement, the former holders of MiaMed's capital stock received an aggregate of $6.5 million, comprised of (i) approximately $1.8 million in cash (plus MiaMed's cash and cash equivalents at closing and less any of MiaMed's unpaid third-party fees and expenses related to the transaction), and (ii) 825,603 shares of the Company's Common Stock. In addition, the Company also agreed to pay up to an additional $83.0 million in connection with the achievement of certain clinical, regulatory and commercial milestones, for a potential aggregate deal value of $89.5 million. The Company evaluated the transaction based on the guidance of Accounting Standard Codification ("ASC") 805, Business Combinations and concluded that it only acquired inputs and did not acquire any processes. The Company will need to develop its own processes in order to produce an output. Therefore, the Company accounted for the transaction as an asset acquisition and accordingly $6.5 million was expensed to research and development. Acquisition of Scioderm, Inc. In September 2015, the Company acquired Scioderm Inc., ("Scioderm"), a privately-held biopharmaceutical company focused on developing innovative therapies for treating the rare disease EB. The acquisition potentially leveraged the Scioderm development team's EB expertise with the Company's global clinical infrastructure to advance SD-101 toward regulatory approvals and the Company's commercial, patient advocacy, and medical affairs infrastructure to support a successful global launch. The acquisition of Scioderm was accounted for as a purchase of a business in accordance with ASC 805 Business Combinations. At the end of the first quarter of 2017, the Company achieved 100% enrollment in the Phase 3 clinical study of SD-101 and the milestone payment of $10 million due for this event, was paid in April 2017. On September 13, 2017, the Company reported that top-line data from the randomized, double-blind, placebo-controlled Phase 3 clinical study (ESSENCE, SD-005) to assess the efficacy and safety of the novel topical wound-healing agent SD-101 did not meet the primary endpoints or secondary endpoints in participants with EB. Based on these top-line data, the Company has no current plans to invest in any additional clinical studies or commercial preparation activities for SD-101. For additional information, see "— Note 1. Description of Business." The associated impairment of Scioderm IPR&D is discussed in "— Note 4. Goodwill and Intangible Assets." For additional information, see "— Note 4. Goodwill and Intangible Assets." Acquisition of Callidus Biopharma, Inc. In November 2013, the Company acquired Callidus a privately-held biologics company focused on developing best-in-class ERTs for LSDs with its lead ERT ATB200 for Pompe disease in late preclinical development. The acquisition of the Callidus assets and technology complements Amicus' CHART® platform for the development of next generation ERTs. The fair value of the contingent acquisition consideration payments was estimated by applying a probability-based income approach utilizing an appropriate discount rate. Key assumptions include discount rate and various probability factors. This estimation was based on significant inputs that are not observable in the market, referred to as Level 3 inputs. Some of the more significant assumptions used in the valuation include (i) the probability and timing related to the achievement of certain developmental milestones and (ii) and the discount rate. See "— Note 10. Assets and Liabilities Measured at Fair Value", for additional discussion regarding fair value measurements of the contingent acquisition consideration payable. The Company determined the fair value of the contingent consideration to be $25.4 million at December 31, 2017, of which $8.4 million is payable over the next twelve months and $17.0 million is payable beyond the next twelve months, resulting in an increase in the contingent consideration payable and related expense of $15.7 million in the year ended December 31, 2017. The expense is recorded in the Consolidated Statement of Operations within the changes in fair value of contingent consideration line item. For further information, see "— Note 4. Goodwill and Intangible Assets."

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets

Goodwill and Intangible Assets

4. Goodwill and Intangible Assets

In connection with the acquisitions, the Company initially recognized IPR&D of $486.7 million and goodwill of $197.8 million. Intangible assets related to IPR&D assets are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate a reduction in the fair value of the IPR&D assets below their respective carrying amounts.

Goodwill and intangible assets are assessed annually for impairment on October 1 and whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined that the full carrying amount of an asset is not recoverable, an impairment loss is recorded in the amount by which the carrying amount of the asset exceeds its fair value. As discussed in "— Note 1. Description of Business", in September 2017, the Company reported that top-line data from the randomized, double-blind, placebo-controlled Phase 3 clinical study (ESSENCE, SD-005) to assess the efficacy and safety of the novel topical wound-healing agent SD-101 did not meet the primary endpoints or secondary endpoints in participants with EB. This event led to an assessment to determine if an impairment had occurred for goodwill and IPR&D. Based on tests for impairment, the Company determined that IPR&D had been impaired, however goodwill was not impaired based on qualitative and market capitalization tests performed. The loss on impairment of IPR&D is recorded within Loss on Impairment of Assets within the Consolidated Statements of Operations.

The following table represents the changes in IPR&D for the year ended December 31, 2017:

	(in millions)
Balance at December 31, 2016	$	486.7
Impairment in IPR&D related to Scioderm		(463.7	)

Balance at December 31, 2017	$	23.0

The following table represents the changes in Goodwill for the year ended December 31, 2017:

	(in millions)
Balance at December 31, 2016	$	197.8
Change in goodwill		—

Balance at December 31, 2017	$	197.8

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Cash, Money Market Funds and Marketable Securities

12 Months Ended

Dec. 31, 2017

Cash, Money Market Funds and Marketable Securities

Cash, Money Market Funds and Marketable Securities

5. Cash, Money Market Funds and Marketable Securities

As of December 31, 2017, the Company held $49.1 million in cash and cash equivalents and $309.5 million of available-for-sale securities which are reported at fair value on the Company's Consolidated Balance Sheets. Unrealized gains and losses are reported within accumulated other comprehensive income/ (loss) in the statements of comprehensive loss. If a decline in the fair value of a marketable security below the Company's cost basis is determined to be other than temporary, such marketable security is written down to its estimated fair value as a new cost basis and the amount of the write-down is included in earnings as an impairment charge. To date, only temporary impairment adjustments have been recorded.

The Company regularly invests excess operating cash in deposits with major financial institutions, money market funds, notes issued by the U.S. government, as well as fixed income investments and U.S. bond funds both of which can be readily purchased and sold using established markets. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated as many of these securities are either government backed or of the highest credit rating. Investments that have original maturities or greater than 3 months but less than 1 year are classified as short-term and investments with maturities that are greater than 1 year are classified as long-term. As of December 31, 2017, all the investments were classified as short-term on the Company's Consolidated Balance Sheets.

The Company transacts business in various foreign countries and therefore, is subject to risk of foreign currency exchange rate fluctuations. As such, in June 2016 the Company entered into a forward contract to economically hedge transactional exposure associated with commitments arising from trade accounts payable denominated in a currency other than the functional currency of the respective operating entity. The Company does not designate these forward contracts as hedging instruments under applicable accounting guidance and, therefore, changes in fair value are recorded within other income (expense) in the Consolidated Statements of Operations, with the corresponding liability in current liabilities on the Consolidated Balance Sheet. For the years ended December 31, 2017 and 2016, we recognized a loss of $0.2 million and $0.3 million, respectively, related to the foreign currency forward contract not designated as hedging instruments in other expense in the Consolidated Statements of Operations. For the year ended December 31, 2016, the Company also recognized a corresponding liability of $0.3 million as other current liability in the Consolidated Balance Sheets. As the forward contract settled in June 2017, there was no liability for the year ended December 31, 2017.

Cash and available for sale securities consisted of the following as of December 31, 2017 and December 31, 2016 (in thousands):

	As of December 31, 2017
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	49,060	$	—	$	—		$	49,060
Corporate debt securities, current portion		199,314		1		(303	)		199,012
Commercial paper		79,878		—		(75	)		79,803
Asset-backed securities		30,346		—		(59	)		30,287
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	358,998	$	1	$	(437	)	$	358,562


Included in cash and cash equivalents	$	49,060	$	—	$	—		$	49,060
Included in marketable securities		309,938		1		(437	)		309,502

Total cash and marketable securities	$	358,998	$	1	$	(437	)	$	358,562

	As of December 31, 2016
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	187,026	$	—	$	—		$	187,026
Corporate debt securities, current portion		74,564		2		(31	)		74,535
Commercial paper		68,258		132		—			68,390
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	330,248	$	134	$	(31	)	$	330,351


Included in cash and cash equivalents	$	187,026	$	—	$	—		$	187,026
Included in marketable securities		143,222		134		(31	)		143,325

Total cash and marketable securities	$	330,248	$	134	$	(31	)	$	330,351

For the years ended December 31, 2017 and 2016, there were no realized gains or losses. The cost of securities sold is based on the specific identification method.

Unrealized loss positions in the available for sale securities as of December 31, 2017 and December 31, 2016 reflect temporary impairments that have been in a loss position for less than twelve months and as such are recognized in other comprehensive gain/ (loss). The fair value of these available for sale securities in unrealized loss positions was $295.1 million and $58.7 million as of December 31, 2017 and 2016, respectively.

The Company holds available-for-sale investment securities which are reported at fair value on the Company's balance sheet. Unrealized gains and losses are reported within accumulated other comprehensive income ("AOCI") in the statements of comprehensive loss.

Inventories

12 Months Ended

Dec. 31, 2017

Inventories

Inventories

6. Inventories

Inventories consist of work in process and finished goods related to the manufacture of GALAFOLD. The following table summarizes the components of inventories at December 31, 2017 (in thousands):

	December 31, 2017		December 31, 2016
Work-in-process	$	3,843	$	3,308
Finished goods		780		108

Total inventories	$	4,623	$	3,416

Inventory manufactured prior to approval was expensed to research and development. Inventories are reviewed periodically to identify slow-moving or obsolete inventory based on projected sales activity, as well as product shelf-life. In evaluating the recoverability of inventories produced, the Company considers the probability that revenue will be obtained from the future sale of the related inventory. Inventory becomes obsolete when it has aged past its shelf-life, cannot be recertified and is no longer usable or able to be sold, or the inventory has been damaged. In such instances, a full reserve would be taken against such inventory. Expired inventory is disposed of and the related costs are recognized as cost of product sales in the consolidated statement of operations. There have been no write-downs of inventory from the time inventory was first capitalized nor have any inventory reserves been recorded to date.

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property and Equipment

Property and Equipment

7. Property and Equipment

Property and equipment consist of the following (in thousands):

	December 31,
	2017			2016
Property and equipment consist of the following:
Computer equipment	$	3,746		$	3,511
Computer software		1,236			1,347
Research equipment		6,379			7,465
Furniture and fixtures		2,992			3,018
Leasehold improvements		7,193			6,970
Construction in progress		31			—

		21,577			22,311
Less accumulated depreciation		(12,515	)		(12,495	)

	$	9,062		$	9,816

Depreciation expense was $3.6 million and $3.2 million for the years ended December 31, 2017 and 2016, respectively, and includes depreciation expenses related to capital lease obligations.

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2017

Accounts Payable and Accrued Expenses

Accounts Payable and Accrued Expenses

8. Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following (in thousands):

	December 31,
	2017		2016
Accounts payable	$	7,867	$	12,905
Accrued professional fees		5,845		5,079
Accrued contract manufacturing & contract research costs		4,632		8,042
Accrued compensation and benefits		19,620		9,686
Accrued facility costs		1,665		1,740
Accrued program fees		5,707		—
Foreign currency forward contract		—		265
Capital lease, short term portion		307		283
Royalties payable		2,529		510
Accrued interest		313		208
Accrued other		5,405		2,290

	$	53,890	$	41,008

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

Stockholders' Equity

Stockholders' Equity

9. Stockholders' Equity

Common Stock and Warrants

As of December 31, 2017, the Company was authorized to issue 250 million shares of common stock. Dividends on common stock will be paid when, and if, declared by the board of directors. Each holder of common stock is entitled to vote on all matters that are appropriate for stockholder voting and is entitled to one vote for each share held.

As discussed in "— Note 1. Business," On February 15, 2018, the Company announced the pricing of an underwritten offering of 19,354,839 shares of its common stock at $15.50 per shares, resulting in gross proceeds of $300.0 million, before deducting underwriting discounts and commissions and offering expenses payable by the Company. The offering closed on February 21, 2018 and the Company received net proceeds of $282.0 million from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by the Company. The offering is expected to close on February 21, 2018, subject to customary closing conditions. J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC were acting as joint lead book-running managers, Cowen and Leerink Partners were acting as co-book-running managers, and BofA Merrill Lynch was acting as lead co-manager for the offering.

As discussed in "— Note 1. Business," in July 2017, the Company entered into the Underwriting Agreement with J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC, as representatives of the several underwriters set forth on Schedule 1 thereto, relating to the Offering. Under the terms of the Underwriting Agreement, the Company issued and sold 21,122,449 shares at a price to the public of $12.25 per share, resulting in gross proceeds of $258.8 million, before deducting underwriting discounts and commissions and offering expenses payable by the Company. The Offering closed on July 18, 2017 and the Company received net proceeds from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by the Company of $243.0 million.

As discussed in "— Note 11. Debt Instruments and Related Party Transactions", in December 2016, the Company issued $250 million aggregate principal amount of 3.0% unsecured Convertible Senior Notes due 2023 (the "Convertible Notes), in a private offering. The Notes will mature on December 15, 2023, unless earlier repurchased, redeemed, or converted in accordance with their terms. The Notes are convertible at the option of the holders, under certain circumstances and during certain periods, into cash, shares of the Company's common stock, par value $0.01 per share ("Common Stock"), or a combination thereof. Prior to the close of business on the business day immediately preceding September 15, 2023, the Notes are convertible at the option of the holders of the Notes only under certain conditions. On or after September 15, 2023, until the close of business on the second business day immediately preceding the maturity date, holders of the Notes may convert their Notes at their option at the conversion rate then in effect, irrespective of these conditions. The Company will settle conversions of the Notes by paying or delivering, as the case may be, cash, shares of Common Stock, or a combination of cash and shares of Common Stock, at the Company's election. The conversion rate will initially be 163.3987 shares of Common Stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $6.12 per share of Common Stock). The conversion rate is subject to customary adjustments upon the occurrence of certain events.

Beginning in April 2016 and through July 2016, the Company sold 15.0 million shares of Common Stock under an ATM equity program with Cowen and Company, LLC ("Cowen") acting as sales agent. Cowen was compensated at a fixed commission rate up to 3.0%. The ATM sales agreement resulted in net proceeds of $97.1 million, after Cowen's commission of $2.7 million and other expenses of $0.2 million. The Company has completed all sales under the ATM equity program.

As discussed in "— Note 11. Debt instruments and Related Party Transactions," the Company issued approximately 1.8 million and 1.3 million of warrants in February 2016 and June 2016, respectively. The closing balance of the warrants was $16.1 million as of December 31, 2016 and is recorded within equity on the Consolidated Balance Sheets.

As discussed in "— Note 3. Acquisitions, in July 2016, the Company entered into an Agreement and Plan of Merger (the "MiaMed Agreement") with MiaMed. Under the terms of the MiaMed Agreement, the former holders of MiaMed's capital stock received an aggregate of $6.5 million, comprised of (i) approximately $1.8 million in cash (plus MiaMed's cash and cash equivalents at closing and less any of MiaMed's unpaid third-party fees and expenses related to the transaction), and (ii) 825,603 shares of the Company's Common Stock. In addition, the Company also agreed to pay up to an additional $83.0 million in connection with the achievement of certain clinical, regulatory and commercial milestones, for a potential aggregate deal value of $89.5 million.

In September 2015, the Company acquired Scioderm with cash and stock. As part of the acquisition, the Company paid holders of Scioderm an amount equal to $223.9 million, of which approximately $141.1 million was paid in cash and approximately $82.8 million was paid through the issuance of 5.9 million newly issued shares.

Nonqualified Cash Plan

The Company's Deferral Plan, (the "Deferral Plan") provides certain key employees and members of the Board of Directors as selected by the Compensation Committee, with an opportunity to defer the receipt of such participant's base salary, bonus and director's fees, as applicable. The Deferral Plan is intended to be a nonqualified deferred compensation plan that complies with the provisions of Section 409A of the Internal Revenue Code of 1986 as amended.

The following table summarizes the deferred compensation amounts under the Deferral Plan as of December 31, 2017 and 2016, respectively (in thousands):

	Year ended December 31,
	2017		2016
Deferred compensation investment	$	2,248	$	1,469
Deferred compensation liability	$	2,258	$	1,479
Investment income	$	66	$	34
Unrealized gain	$	92	$	32

Deferral Plan investment assets are classified as trading securities and are recorded at fair value with changes in the investments' fair value recognized in AOCI in the period they occur. Deferred compensation liability amounts under the Deferral Plan are included in other long-term liabilities.

Equity Incentive Plans

The Company's Equity Incentive Plans consist of the Amended and Restated 2007 Equity Incentive Plan (the "Plan") and the 2007 Director Option Plan (the "2007 Director Plan"). The Plan provides for the granting of restricted stock and options to purchase common stock in the Company to employees, advisors and consultants at a price to be determined by the Company's board of directors. The Plan is intended to encourage ownership of stock by employees and consultants of the Company and to provide additional incentives for them to promote the success of the Company's business. The 2007 Director Plan is intended to promote the recruiting and retention of highly qualified eligible directors and strengthen the commonality of interest between directors and stockholders by encouraging ownership of common stock of the Company. Under the provisions of each plan, no option will have a term in excess of 10 years.

The Board of Directors, or its committee, is responsible for determining the individuals to be granted options, the number of options each individual will receive, the option price per share, and the exercise period of each option. Options granted pursuant to the Plan generally vest 25% on the first year anniversary date of grant plus an additional 1/48th for each month thereafter and may be exercised in whole or in part for 100% of the shares vested at any time after the date of grant. Options under the 2007 Director Plan may be granted to new directors upon joining the Board and vest in the same manner as options under the Plan. In addition, options are automatically granted to all directors at each annual meeting of stockholders and vest on the date of the annual meeting of stockholders of the Company in the year following the year during which the options were granted.

As of December 31, 2017, the Company has reserved up to 7,855,550 shares for issuance under the Plan and the 2007 Director Plan.

Stock Option Grants

The Company adopted the fair value method of measuring stock-based compensation, using the fair value of each equity award granted. The Company chose the "straight-line" attribution method for allocating compensation costs and recognized the fair value of each stock option on a straight-line basis over the vesting period of the related awards.

The Company uses the Black-Scholes option pricing model when estimating the grant date fair value for stock-based awards. Use of a valuation model requires management to make certain assumptions with respect to selected model inputs. Expected volatility was based on our historical volatility since our initial public offering in May 2007. Beginning in the third quarter of 2017, the average expected life was determined using our actual historical data versus a "simplified" method used in prior quarters. The "simplified" method of estimating the expected exercise term uses the mid-point between the vesting date and the end of the contractual term. In earlier quarters, we did not have sufficient reliable exercise data to justify a change from the use of the "simplified" method of estimating the expected exercise term of employee stock option grants. The impact from this change was not material. The risk-free interest rate is based on U.S. Treasury, zero-coupon issues with a remaining term equal to the expected life assumed at the date of grant. Forfeitures are estimated based on voluntary termination behavior, as well as a historical analysis of actual option forfeitures.

The weighted average assumptions used in the Black-Scholes option pricing model are as follows:

	Years Ended December 31,
	2017			2016			2015
Expected stock price volatility		82.8	%		81.3	%		75.9	%
Risk free interest rate		2.0	%		1.5	%		1.7	%
Expected life of options (years)		6.18			6.25			6.25
Expected annual dividend per share	$	0.00		$	0.00		$	0.00

The weighted average grant-date fair value per share of options granted during 2017, 2016 and 2015 were $5.09, $5.28 and $7.51, respectively.

The following table summarizes information about stock options outstanding:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
	(in thousands)						(in millions)
Options outstanding, December 31, 2014		10,020.7		$	5.02
Granted		3,917.2		$	11.61
Exercised		(2,070.3	)	$	5.43
Forfeited		(138.4	)	$	7.76

Options outstanding, December 31, 2015		11,729.2		$	7.11
Granted		5,114.1		$	7.67
Exercised		(723.1	)	$	4.20
Forfeited		(622.7	)	$	8.62

Options outstanding, December 31, 2016		15,497.5		$	7.37
Granted		3,695.3		$	7.17
Exercised		(2,878.7	)	$	5.67
Forfeited		(1,133.0	)	$	9.55

Options outstanding, December 31, 2017		15,181.1		$	7.48	7.2 years	$	105.8


Vested and unvested expected to vest, December 31, 2017		14,398.5		$	7.45	7.1 years	$	100.9
Exercisable at December 31, 2017		7,985.6		$	7.05	6.0 years	$	59.1

The aggregate intrinsic value of options exercised during the years ended December 31, 2017, 2016 and 2015 was $20.8 million, $2.6 million and $14.7 million respectively. Cash proceeds from stock options exercised during the years ended December 31, 2017, 2016, and 2015 were $16.3 million, $3.0 million, and $11.2 million, respectively. As of December 31, 2017, the total unrecognized compensation cost related to non-vested stock options granted was $31.9 million and is expected to be recognized over a weighted average period of 2.5 years.

Restricted Stock Units ("RSUs")and Performance-Based Restricted Stock Units

RSUs awarded under the Plan are generally subject to graded vesting and are contingent on an employee's continued service. RSUs are generally subject to forfeiture if employment terminates prior to the release of vesting restrictions. The Company expenses the cost of the RSUs, which is determined to be the fair market value of the shares of Common Stock underlying the RSUs at the date of grant, ratably over the period during which the vesting restrictions lapse.

A summary of non-vested RSU activity under the Plan for the year ended December 31, 2017 is as follows:

	Number of Share			Weighted Average Grant Date Fair Value		Weighted Average Remaining Years		Aggregate Intrinsic Value
	(in thousands)							(in millions)
Non-vested units as of December 31, 2015		478.5		$	10.38
Granted		582.7		$	6.21
Vested		(281.9	)	$	8.73
Forfeited		(34.9	)	$	7.71

Non-vested units as of December 31, 2016		744.4		$	7.86
Granted		2,348.7		$	5.69
Vested		(318.2	)	$	9.23
Forfeited		(199.8	)	$	6.24

Non-vested units as of December 31, 2017		2,575.1		$	5.85		2.47	$	37.1

On December 30, 2016, the Compensation Committee approved a form of Performance-Based Restricted Stock Unit Award Agreement (the "Performance-Based RSU Agreement"), to be used for performance-based RSUs granted to participants under the Amended and Restated Amicus Therapeutics, Inc. 2007 Equity Incentive Plan, including named executive officers. Certain awards under the form of Performance-Based RSU Agreement were granted in January 2017. The table above includes 401,413 market performance-based restricted stock units ("MPRSUs") granted to executives. Vesting of these awards is contingent upon the Company meeting certain total shareholder return ("TSR") levels as compared to a select peer group over the next three years. The MPRSUs cliff vest at the end of the three-year period and have a maximum potential to vest at 200% (802,826 shares) based on TSR performance. The related share-based compensation expense is determined based on the estimated fair value of the underlying shares on the date of grant and is recognized straight-line over the vesting term. The estimated fair value per share of the MPRSUs was $8.08 and was calculated using a Monte Carlo simulation model. The table above also includes 401,413 performance based awards that will vest over the next three years based on the Company achieving certain clinical milestones.

For the year ended December 31, 2017, 0.3 million of the RSUs vested and all non-vested units are expected to vest over their normal term. As of December 31, 2017, there was $11.4 million of total unrecognized compensation cost related to unvested RSUs with service-based vesting conditions. These costs are expected to be recognized over a weighted average period of 2.47 years.

Compensation Expense Related to Equity Awards

The following table summarizes the equity-based compensation expense recognized in the statements of operations (in thousands):

	Years Ended December 31,
	2017		2016		2015
Equity compensation expense recognized in:
Research and development expense	$	10,328	$	8,071	$	4,600
Selling, general and administrative expense		12,773		9,433		5,372

Total equity compensation expense	$	23,101	$	17,504	$	9,972

Assets and Liabilities Measured at Fair Value

12 Months Ended

Dec. 31, 2017

Assets and Liabilities Measured at Fair Value

Assets and Liabilities Measured at Fair Value

10. Assets and Liabilities Measured at Fair Value

The Company's financial assets and liabilities are measured at fair value and classified within the fair value hierarchy which is defined as follows:

Level 1 — Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2 — Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly.

Level 3 — Inputs that are unobservable for the asset or liability.

A summary of the fair value of the Company's recurring assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of December 31, 2017 are identified in the following table (in thousands):

	Level 2		Total
Assets:
Commercial paper	$	79,803	$	79,803
Asset-back securities		30,287		30,287
Corporate debt securities		199,012		199,012
Money market funds		2,598		2,598

	$	311,700	$	311,700

	Level 2		Level 3		Total
Liabilities:
Contingent consideration payable	$	—	$	25,400	$	25,400
Deferred compensation plan liability		2,258		—		2,258

	$	2,258	$	25,400	$	27,658

A summary of the fair value of the Company's assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of December 31, 2016 are identified in the following table (in thousands):

	Level 2		Total
Assets:
Commercial paper	$	68,390	$	68,390
Corporate debt securities		74,535		74,535
Money market funds		1,829		1,829

	$	144,754	$	144,754

	Level 2		Level 3		Total
Liabilities:
Contingent consideration payable	$	—	$	269,722	$	269,722
Derivative liability		265		—		265
Deferred compensation plan liability		1,479		—		1,479

	$	1,744	$	269,722	$	271,466

See "— Note 11. Debt Instruments and Related Party Transactions" for the carrying amount and estimated fair value of the Company's Convertible Notes due in 2023. The Company did not have any Level 3 assets as of December 31, 2017 or 2016. The Company did not have any transfers between the Levels during the year ended December 31, 2017 and December 31, 2016.

Cash, Money Market Funds and Marketable Securities

The Company classifies its cash and money market funds within the fair value hierarchy as Level 1 as these assets are valued using quoted prices in active market for identical assets at the measurement date. The Company considers its investments in marketable securities as available for sale and classifies these assets within the fair value hierarchy as Level 2 primarily utilizing broker quotes in a non-active market for valuation of these securities. No changes in valuation techniques or inputs occurred during the year ended December 31, 2017. No transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy occurred during the year ended December 31, 2017.

Contingent Consideration Payable

As discussed in "— Note 1. Business," on September 13, 2017, the Company reported that top-line data from the randomized, double-blind, placebo-controlled Phase 3 clinical study (ESSENCE, SD-005) to assess the efficacy and safety of the novel topical wound-healing agent SD-101 did not meet the primary endpoints or secondary endpoints in participants with EB. Based on these top-line data, the Company has no current plans to invest in any additional clinical studies or commercial preparation activities for SD-101. As such, the contingent consideration related to Scioderm is no longer payable as of September 30, 2017.

The contingent consideration payable resulted from the acquisition of Callidus, as discussed in "— Note 3. Acquisitions." The most recent valuation was determined using a probability weighted discounted cash flow valuation approach. Using this approach, expected future cash flows are calculated over the expected life of the agreement, are discounted, and then exercise scenario probabilities are applied. The valuation is performed quarterly. Gains and losses are included in the statement of operations.

As discussed in "— Note 3. Acquisitions," on July 5, 2016, the Company entered into the MiaMed Agreement with MiaMed. MiaMed is a pre-clinical biotechnology company focused on developing protein replacement for CDKL5 and related diseases. Under the terms of the MiaMed Agreement, the Company agreed to pay up to an additional $83.0 million in connection with the achievement of certain clinical, regulatory and commercial milestones, for a potential aggregate deal value of $89.5 million. The MiaMed Agreement was accounted for as an asset acquisition and as such the Company determined that a liability for future milestone payments is not required to be recorded until the actual contingencies are met and will be recorded to research and development expenses when the contingency is resolved.

The contingent consideration payable for Callidus has been classified as a Level 3 recurring liability as its valuation requires substantial judgment and estimation of factors that are not currently observable in the market. If different assumptions were used for the various inputs to the valuation approach the estimated fair value could be significantly higher or lower than the fair value the Company determined. The Company may be required to record losses in future periods, including expenses related to CDKL5.

On February 7, 2018, the Company announced positive results from the global Phase 1/2 clinical study (ATB200-02) to investigate ATB200/AT2221 in patients with Pompe disease. As a result of these positive results, the probability of success of ATB200 was increased to 71%-100% at December 31, 2017, which drove the increase in fair value of the liability. With these data, the Company plans to continue a series of collaborative discussions with regulators in the US and EU. This event was considered in the calculation of the Contingent Consideration as of December 31, 2017.

The following significant unobservable inputs were used in the valuation of the contingent consideration payable of Callidus for the ATB-200 Pompe program:

Contingent Consideration Liability	Fair value as of December 31, 2017	Valuation Technique	Unobservable Input	Range
			Discount rate	11.5%
Clinical and regulatory milestones	$25.0 million	Probability weighted discounted cash flow	Probability of achievement of milestones	71.0% - 100.0%
			Projected year of payments	2018 - 2022

Contingent consideration liabilities are remeasured to fair value each reporting period using projected revenues, discount rates, probabilities of payment and projected payment dates. Projected contingent payment amounts related to clinical and regulatory based milestones are discounted back to the current period using a discounted cash flow model. Revenue-based payments are valued using a monte-carlo valuation model, which simulates future revenues during the earn out-period using management's best estimates. Projected revenues are based on our most recent internal operational budgets and long-range strategic plans. Increases in projected revenues and probabilities of payment may result in higher fair value measurements. Increases in discount rates and the time to payment may result in lower fair value measurements. Increases or decreases in any of those inputs together, or in isolation, may result in a significantly lower or higher fair value measurement. There is no assurance that any of the conditions for the milestone payments will be met.

The following table shows the change in the balance of contingent consideration payable for the year ended December 31, 2017 and 2016, respectively (in thousands):

	Year ended December 31,
	2017			2016
Balance, beginning of the period	$	269,722		$	274,077
Payment of contingent consideration in cash		(10,000	)		(5,000	)
Payment of contingent consideration in stock		—			(6,115	)
Unrealized change in fair value change during the period, included in Statement of Operations		(234,322	)		6,760

Balance, end of the period	$	25,400		$	269,722

Deferred Compensation Plan- Investment and Liability

As disclosed in "— Note 9. Stockholders' Equity," the Deferral Plan provides certain key employees and members of the Board of Directors with an opportunity to defer the receipt of such participant's base salary, bonus and director's fees, as applicable. Deferral Plan assets are classified as trading securities and recorded at fair value with changes in the investments' fair value recognized in the period they occur. The asset investments consist of market exchanged mutual funds. The Company considers its investments in marketable securities, as available-for-sale and classifies these assets and related liability within the fair value hierarchy as Level 2 primarily utilizing broker quotes in a non-active market for valuation of these securities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Debt Instruments and Related Party Transactions

12 Months Ended

Dec. 31, 2017

Debt Instruments and Related Party Transactions

Debt Instruments and Related Party Transactions

11. Debt Instruments and Related Party Transactions

October 2015 and February 2016 Notes and Warrants Purchase Agreement

In October 2015, the Company entered into the October 2015 Purchase Agreement with Redmile, who beneficially owned approximately 6.7% of the Common Stock as of December 31, 2015, whereby it sold, on a private placement basis, (a) $50.0 million aggregate principal amount of its unsecured promissory notes ("Notes") and (b) five-year warrants ("Warrants") for 1.3 million shares of Common Stock. The payment terms under the purchase agreement contained two installments, the first $15.0 million in October 2017 and the balance $35.0 million in October 2020. Interest was payable at 4.1% on a monthly basis over the term of the loan. Due to the embedded redemption (put and/or call) features in the note agreement, it was determined that the fair value of the warrants should be bifurcated from the value of the notes payable and recorded as a debt discount. The relative fair value of the warrants and the debt discount as related to the October 2015 purchase agreement was determined to be $8.8 million.

This Purchase Agreement was modified in February 2016 when the Company entered into a Note and Warrant Purchase Agreement (the "February 2016 Purchase Agreement") with Redmile for an aggregate amount of up to $75.0 million. The Company agreed with Redmile that in full consideration of the purchase price for the notes issued under the October 2015 Purchase Agreement, Redmile surrendered for cancellation all notes and warrants acquired from the October 2015 Purchase Agreement and the Company paid Redmile any unpaid interest accrued thereunder. Pursuant to the February 2016 agreement, at closing, it sold, on a private placement basis (a) $50.0 million aggregate principal amount of unsecured promissory notes ("Initial Notes") and (b) five year warrants to purchase up to 37 shares of the Company's Common Stock for every $1,000 of the principal amount of Initial Notes purchased ("Initial Warrants"), for an aggregate of up to 1,850,000 shares of Common Stock issuable under the Initial Warrants. The payment terms contained two installments, the first $15.0 million in October 2017 and the balance $35.0 million in October 2021. The interest rate was 3.875% and payable upon of maturity. This transaction was accounted for as a debt modification in accordance with ASC 470-50. The incremental fair value between the warrants that were cancelled and the February issued warrants of $3.5 million was recorded as additional unamortized debt discount on the balance sheet and added to the prior warrant balance within equity.

The Notes mentioned above were cancelled in December 2016. For more details, refer to section December 2016 Note Purchase Agreement below in this footnote.

June 2016 Amended Purchase Agreement

In June 2016, following the marketing approval for migalastat in Europe, the Company entered into the Amended Purchase Agreement with Redmile. Such amendment joined GCM to the February 2016 Purchase Agreement. Pursuant to the Amended Purchase Agreement, the Company sold an additional $30 million unsecured promissory notes and five year warrants to purchase up to purchase up to 42 shares of our Common Stock, par value $0.01 per share for every $1,000 of the principal amount of additional notes purchased, for an aggregate of up to 1,260,000 shares of Common Stock issuable from the additional warrants. The payment was due in October 2021. The interest rate was 3.875% and payable upon of maturity. The Notes mentioned above were cancelled in December 2016. For more details, refer to section December 2016 Note Purchase Agreement below in this footnote.

December 2016 Note Purchase Agreement

On December 15, 2016, the Company entered into a Note Purchase Agreement ("Note Purchase Agreement") with GCM and RedMile, pursuant to which the Company agreed to prepay all outstanding principal and accrued and unpaid interest on the notes issued by the Company and held by GCM and Redmile. Such prepayment was made in December, 2016. The Note Purchase Agreement did not cancel the warrants, under the Amended Purchase Agreement. The net loss on extinguishment of the debt was $13.3 million and is included as loss on extinguishment in the Consolidated Statement of Operations for the year ended December 31, 2016.

2016 Convertible Debt

In December, 2016, the Company issued at par value $250 million aggregate principal amount of unsecured Convertible Senior Notes due 2023 (the "Convertible Notes"), which included the exercise in full of the $25 million over-allotment option granted to the initial purchasers of the Notes, in a private offering to qualified institutional buyers pursuant to Rule 144A under the Securities Act. Interest is payable semiannually on June 15 and December 15 of each year, beginning on June 15, 2017. The Notes will mature on December 15, 2023, unless earlier repurchased, redeemed, or converted in accordance with their terms. The Notes are convertible at the option of the holders, under certain circumstances and during certain periods, into cash, shares of the Company's common stock or a combination thereof and may be settled as described below. The net proceeds from the Note Offering were $243.0 million, after deducting fees and estimated expenses payable by the Company. In addition, the Company used approximately $13.5 million of the net proceeds from the issuance of the Convertible Notes to pay the cost of the capped call transactions ("Capped Call Confirmations") that the Company entered into in connection with the issuance of the Convertible Notes.

The Convertible Notes are governed by an indenture dated December 21, 2016 (the "Indenture") by and between Amicus and Wilmington Trust, National Association, as trustee.

The Convertible Notes are initially convertible into approximately 40,849,675 shares of the Company's common stock under certain circumstances prior to maturity at a conversion rate of 163.3987 shares per $1,000 principal amount of Convertible Notes, which represents a conversion price of approximately $6.12 per share of Common Stock, subject to adjustment under certain conditions. Holders may convert their Convertible Notes at their option at specified times prior to the maturity date of December 15, 2023, only if:


	•	during any fiscal quarter commencing after March 31, 2017, if the last reported sale price of the Company's common stock for at least 20 trading days in the period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter is equal to or more than 130% of the conversion price of the Convertible Notes on the last day of such preceding fiscal quarter;
	•	a Holder submits its Convertible Notes for conversion during the five business day period following any five consecutive trading day period in which the trading price for the Convertible Notes, per $1,000 principal amount of the Convertible Notes, for each such trading day was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate of the Convertible Notes on such date; or
	•	the Company issues to all or substantially all of the holders of common stock rights options or warrants entitling then them for a period of not more than 60 calendar days after the date of such issuance to subscribe for or purchase shares of the Common Stock, at a price per share less than the average of the Last Reported Sale Prices of the Common Stock for the 10 consecutive Trading Day period ending on, and including, the Trading Day immediately preceding the date of announcement of such issuance or distributes to all or substantially all holders of the Common Stock the Company's assets, debt securities or rights to purchase the Company's securities which distribution has a per share value of exceeding 10% of the Last Reported Sale Price of the Common Stock on the Trading Day immediately preceding the date of announcement of such distribution
	•	the Company enters into specified corporate transactions.
	•	the Company has had a call for redemption, the holder can convert up until the second trading day immediately preceding the redemption date

The Convertible Notes will be convertible, at the option of the note holders, regardless of whether any of the foregoing conditions have been satisfied, on or after September 15, 2023 at any time prior to the close of business on the second scheduled trading day immediately preceding the stated maturity date of December 15, 2023.

The last reported sale price of the Company's Common Stock was equal to or more than 130% of the conversion price of the Convertible Notes for at least 20 trading days of the 30 consecutive trading days ending on the last day of the fourth quarter of 2017. As a result, the Convertible Notes are currently convertible into the Company's Common stock as discussed above.

Upon the occurrence of a make-whole fundamental change or if the Company call all or any portion of the Convertible Notes for redemption prior to July 1, 2020, the Company will, in certain circumstances, increase the conversion rate by a number of additional shares for a holder that elects to convert its Convertible Notes in connection with such make-whole fundamental change or during the related redemption period.

Upon conversion, the Company may pay cash, shares of the Company's common stock or a combination of cash and stock, as determined by the Company in its discretion.

The Company accounts for the Convertible Notes as a liability and equity component where the carrying value of the liability component will be valued based on a similar instrument. In accounting for the issuance of the Convertible Notes, the Company separated the Convertible Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the Convertible Notes as a whole. The excess of the principal amount of the liability component over its carrying amount, referred to as the debt discount, is amortized to interest expense over the seven-year term of the Convertible Notes. The equity component is not re-measured as long as it continues to meet the conditions for equity classification.

In accounting for the issuance of the Convertible Notes, the Company separated the Convertible Notes into liability and equity components based on their relative values. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the Convertible Notes. The difference between the principal amount of the Convertible Notes and the liability component represents the debt discount, which is recorded as a direct deduction from the related debt liability in the Consolidated Balance Sheets and amortized to interest expense using the effective interest method over the seven-year term of the Convertible Notes. The equity component of the Convertible Notes of approximately $88.3 million is included in additional paid-in capital in the Consolidated Balance Sheets and is not remeasured as long as it continues to meet the conditions for equity classification. Additionally, the Company recorded a deferred tax liability of $29.8 million in relation to the Convertible Notes.

The Company incurred transaction costs of approximately $7.5 million, including approximately $6.9 million that was paid from the gross proceeds of the Convertible Notes offering. In accounting for the transaction costs, the Company allocated the total amount incurred to the liability and equity components using the same proportions as the proceeds from the Convertible Notes. Transaction costs attributable to the liability component were recorded as a direct deduction from the related debt liability in the Consolidated Balance Sheets and amortized to interest expense over the seven-year term of the Convertible Notes. Transaction costs attributable to the equity component were netted with the equity component in additional-paid-in-capital.

The Convertible Notes consist of the following as of December 31, 2017 and 2016 (In thousands):

Liability component	2017			2016
Principal	$	250,000		$	250,000
Less: debt discount (1)		(81,566	)		(90,807	)
Less: deferred financing (1)		(4,267	)		(4,729	)

Net carrying value of the debt	$	164,167		$	154,464


(1)	Included in the Consolidated Balance Sheets within Convertible Senior Notes (due 2023) and amortized to interest expense over the remaining life of the Convertible Senior Notes using the effective interest rate method.

The fair value of the debt at December 31, 2017 was approximately $633.4 million.

The following table sets forth total interest expense recognized related to the Convertible Notes for the year ended December 31, 2017 and 2016 (In thousands):

Components	2017			2016
Contractual interest expense	$	7,528		$	208
Amortization of deferred financing		470			26
Amortization of debt discount		9,241			248

Total	$	17,239		$	482


Effective interest rate of the liability component		10.85	%		10.85	%

The Capped Call Confirmations of $13.5 million are expected generally to reduce the potential dilution to the Common Stock upon any conversion of the Convertible Notes and/or offset the cash payments the Company is required to make in excess of the principal amount upon conversion of the Notes in the event that the market price of the Common Stock is greater than the strike price of the Capped Call Confirmations (which initially corresponds to the initial conversion price of the Convertible Notes and is subject to certain adjustments under the terms of the Capped Call Confirmations), with such reduction and/or offset subject to a cap based on the cap price of the Capped Call Confirmations. The Capped Call Confirmations have an initial cap price of $7.20 per share, which represents a premium of approximately 50% over the closing price of the Company's Common Stock on The NASDAQ Global Market on December 15, 2016, and is subject to certain adjustments under the terms of the Capped Call Confirmations. The Capped Call Confirmations will cover, subject to anti-dilution adjustments substantially similar to those applicable to the Convertible Notes, the number of shares of Common Stock that will underlie the Convertible Notes. The Capped Call Confirmations do not meet the criteria for separate accounting as a derivative as they are indexed to the Company's Common Stock. The premiums paid for the Capped Call Confirmations have been included as a net reduction to additional paid-in capital.

Leases

12 Months Ended

Dec. 31, 2017

Leases

Leases

12. Leases

Operating Leases

The Company currently leases office space and research laboratory space in various facilities under operating agreements expiring at various dates through 2025.

The following table contains information about our current significant leased properties as of December 31, 2017:

Location	Approximate Square Feet		Use	Lease expiry date
Cranbury, New Jersey		90,000	Office and laboratory	September 2025
Durham, North Carolina		5,603	Office	June 2018
Buckinghamshire, United Kingdom		9,821	Office	September 2020
Munich, Germany		4,751	Office	April 2022

In addition to the above, we also maintain small offices in the Italy, France, Netherlands, Spain, Japan, Canada and Denmark. We believe that our current office and laboratory facilities are adequate and suitable for our current and anticipated needs. We believe that, to the extent required, we will be able to lease or buy additional facilities at commercially reasonable rates.

Rent expenses for the Company's facilities are recognized over the term of the lease. The Company recognizes rent starting when possession of the facility is taken from the landlord. When a lease contains a predetermined fixed escalation of the minimum rent, the Company recognizes the related rent expense on a straight-line basis and records the difference between the recognized rental expense and the amounts payable under the lease as deferred rent liability. Tenant leasehold improvement allowances are reflected in accrued expenses on the consolidated balance sheets and are amortized as a reduction to rent expense in the statement of operations over the term of the lease.

At December 31, 2017, aggregate annual future minimum lease payments under these leases are as follows:

(in thousands)		2018			2019			2020			2021			2022 and beyond			Total
Minimum lease payments		$	2,762		$	2,575		$	2,472		$	2,240		$	8,467		$	18,516

Rent expense, including fees for utilities and common area maintenances for the years ended December 31, 2017, 2016 and 2015 were $3.9 million, $3.5 million and $2.6 million, respectively.

Capital Leases

In 2016, the Company purchased equipment of approximately $0.9 million through financing arrangements. These financing arrangements include interest of approximately 0.2-5.7%, and lease terms of 36-48 months.

At December 31, 2017, aggregate annual future minimum lease payments under these leases, including interest, are as follows (in thousands):

Years ending December 31:
2018	$	356
2019		134
2020		—
2021		—
2022 and beyond		—

Total principal obligation	$	490

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

Income Taxes

13. Income Taxes

For financial reporting purposes, income (loss) before income taxes includes the following components (in thousands):

	Years Ended December 31,
	2017			2016			2015
United States	$	(440,696	)	$	(174,913	)	$	(123,697	)
Foreign		(8,425	)		(28,868	)		(8,421	)

Total	$	(449,121	)	$	(203,781	)	$	(132,118	)

Following were the components of income tax expense (benefit) for the years ending December 31, 2017 and December 31, 2016:

	2017			2016			2015
Current:
State	$	9		$	7		$	—
Foreign		2,276			—			—
Deferred
Federal		(150,015	)		(1,101	)		—
State		(17,389	)		(2,645	)		—

Total	$	(165,119	)	$	(3,739	)	$	—

A reconciliation of the statutory tax rates and the effective tax rates for the years ended December 31, 2017, 2016 and 2015 are as follows:

	Years Ended December 31,
	2017			2016			2015
Statutory rate		(34	)%		(34	)%		(34	)%
State taxes, net of federal benefit		(5	)		(5	)		(5	)
Permanent adjustments		(1	)		3			2
Contingent consideration		(18	)		—			—
R&D credit		(2	)		(3	)		(3	)
Foreign income tax rate differential		5			2			1
Impact of 2017 Act		27			—			—
Other		5			(1	)		2
Valuation allowance		(14	)		36			37

Net		(37	)%		(2	)%		(0	)%

On December 22, 2017, the US government enacted the Tax Act. The Tax Act significantly revises US tax law by, among other provisions, lowering the US federal statutory income tax rate to 21%, imposing a mandatory one-time transition tax on previously deferred foreign earnings, and eliminating or reducing certain income tax deductions.

ASC 740, Income Taxes requires the effects of changes in tax laws to be recognized in the period in which the legislation is enacted. However, due to the complexity and significance of the Tax Act's provisions, the SEC staff issued SAB 118, which allows companies to record the tax effects of the Tax Act on a provisional basis based on a reasonable estimate, and then, if necessary, subsequently adjust such amounts during a limited measurement period as more information becomes available. The measurement period ends when a company has obtained, prepared, and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year from enactment. The Tax Act did not have a material impact on the Company's financial statements because its deferred temporary differences are fully offset by a valuation allowance and the Company does not have any significant offshore earnings from which to record the mandatory transition tax. The Company recorded an income tax benefit of $2.7 million in the Consolidated Statement of Operations, in connection with the reduction in the statutory corporate income tax rate. The Company operates in a consolidated loss position in its foreign operations, and does not have a one-time tax on accumulated earnings of foreign subsidiaries.

However, given the significant complexity of the Tax Act, anticipated guidance from the US Treasury about implementing the Tax Act, and the potential for additional guidance from the SEC or the FASB related to the Tax Act, these estimates may be adjusted during the measurement period. The Company continues to analyze the changes in certain income tax deductions, assess calculations of earnings and profits in certain foreign subsidiaries, including if those earnings are held in cash or other assets, and gather additional data to compute the full impacts on the Company's deferred and current tax assets and liabilities.

For the year ended December 31, 2017, the Company recorded an income tax benefit of $164.7 million due to the reduction of the deferred tax liability related to Scioderm IPR&D as a result of the announcement of the Phase 3 ESSENCE study.

The Company recorded income tax expense of $2.3 million in 2017 for taxes in foreign and state jurisdictions.

The Company did not recognize interest or penalties related to income tax during the period ended December 31, 2017 and did not accrue for interest or penalties as of December 31, 2017. The Company does not have an accrual for uncertain tax positions as of December 31, 2017. Tax returns for all years 2010 and thereafter are subject to future examination by tax authorities.

Deferred income taxes reflect the net effect of temporary difference between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The significant components of the deferred tax assets and liabilities are as follows (in thousands):

	For Years Ended December 31,
	2017			2016
Deferred tax assets
Intellectual property	$	44,573		$	95,956
Amortization/depreciation		3,082			1,781
Research tax credit		43,382			32,851
Net operating loss carry forwards		221,912			223,758
Deferred revenue		6,158			14,281
Non-cash stock issue		10,751			11,649
Others		7,328			3,358

Gross deferred tax assets		337,186			383,634
Deferred tax liabilities
Business acquisition		(6,465	)		(173,771	)
Royalty payable		(44,573	)		(96,829	)
Convertible notes		(18,991	)		(29,845	)
Advanced R&D payments		(3,069	)		—

Total net deferred tax asset		264,088			83,189
Less valuation allowance		(270,553	)		(256,960	)

Net deferred tax liability	$	(6,465	)	$	(173,771	)

The Company records a valuation allowance for temporary differences for which it is more likely than not that the Company will not receive future tax benefits. At December 31, 2017 and 2016, the Company recorded valuation allowances of $270.6 million and $257.0 million, respectively, representing an increase in the valuation allowance of $13.6 million in 2017 due to the uncertainty regarding the realization of such deferred tax assets, to offset the benefits of net operating losses generated during those years. The deferred tax liability related to business acquisitions pertains to the basis difference in IPR&D acquired by the Company. The Company's policy is to record a deferred tax liability related to acquired IPR&D that may eventually be realized either upon amortization of the asset when the research is completed and a product is successfully launched or the write-off of the asset if it is abandoned or unsuccessful.

As of December 31, 2017, the Company had federal, state, and foreign net operating loss carry forwards ("NOLs") of approximately $777.6 million, $781.8 million, and $47.1 million, respectively. The federal carry forward will expire in 2030 through 2037. Most of the state carry forwards generated prior to 2009 have expired through 2016. The remaining state carry forwards including those generated in 2010 through 2017 will expire in 2030 through 2037. The foreign NOLs have indefinite expiration. Utilization of NOLs may be subject to a substantial limitation pursuant to Section 382 of the Code as well as similar state statutes in the event of an ownership change. Such ownership changes have occurred in the past, and could occur again in the future As a result of these ownership changes, Section 382 places an annual limitation on the amount of NOLs that can be utilized to offset future taxable income each year, which is based on the value of the company at the change date. This limitation could result in expiration of those carry forwards before utilization. In general, an ownership change, as defined by Section 382, results from transactions that increase the ownership of certain stockholders or public groups in the stock of a corporation by more than 50 percentage points over a three year period. The Company completed a detailed study of its cumulative ownership changes for 2017 and determined that in 2017, there was no ownership change in excess of 50%; therefore there was no write-down to net realizable value of the federal NOLs and research and development credits subject to the 382 limitations.

We also have research and experimentation and orphan drug credit carryforwards of approximately $35.2 million and $8.2 million, respectively, which will expire in the years 2023 through 2037. Deferred tax assets for these carryforwards are subject to a full valuation allowance.

Licenses	12 Months Ended
Licenses	Dec. 31, 2017
Licenses
Licenses	14. Licenses The Company acquired rights to develop and commercialize its product candidates through licenses granted by various parties. The following summarizes the Company's material rights and obligations under those licenses: GSK — For discussion of the royalties and milestone payments potentially due to GSK, see "— Note 15. Collaborative Agreements." Mt. Sinai School of Medicine of New York University ("MSSM") — The Company acquired exclusive worldwide patent rights to develop and commercialize migalastat and other pharmacological chaperones for the prevention or treatment of human diseases or clinical conditions by increasing the activity of wild-type and mutant enzymes pursuant to a license agreement with Mt. Sinai School of Medicine ("MSSM") of New York University. Under this agreement, to date, the Company has paid no upfront or annual license fees and there are no milestone or future payments other than royalties on net sales. This agreement expires upon expiration of the last of the licensed patent rights, which will be in 2019, subject to any patent term extension that may be granted, or 2024 if the Company develops a product for combination therapy (pharmacological chaperone plus/ERT) and a patent issues from the pending application covering the combination therapy, subject to any patent term extension that may be granted. Under its license agreements, if the Company owes royalties on net sales for one of its products to more than one of the above licensors, then the Company has the right to reduce the royalties owed to one licensor for royalties paid to another. The amount of royalties to be offset is generally limited in each license and can vary under each agreement. For migalastat, in 2017, the Company incurred $1.1 million of royalty expense under the agreement with MSSM. The Company's rights with respect to these agreements to develop and commercialize migalastat may terminate, in whole or in part, if the Company fails to meet certain development or commercialization requirements or if the Company does not meet its obligations to make royalty payments.

Collaborative Agreements

12 Months Ended

Dec. 31, 2017

Collaborative Agreements

Collaborative Agreements

15. Collaborative Agreements

GSK

In November 2013, Amicus entered into the Revised Agreement with GSK, pursuant to which Amicus has obtained global rights to develop and commercialize migalastat as a monotherapy and in combination with ERT for Fabry disease. The Revised Agreement amends and replaces in its entirety the earlier agreement entered into between Amicus and GSK in July 2012. Under the terms of the Revised Agreement, there was no upfront payment from Amicus to GSK. For migalastat monotherapy, GSK is eligible to receive post-approval and sales-based milestones up to $40 million, as well as tiered royalties in the mid-teens in eight major markets outside the U.S. For the year ended December 31, 2017, the Company incurred approximately $3.9 million of royalty expenses under the revised agreement with GSK.

Under the terms of the Revised Agreement, GSK will no longer jointly fund development costs for all formulations of migalastat.

In evaluating the impact of both the Expanded Collaboration Agreement and the Revised Agreement, the Company applied the accounting guidance regarding the impact of potential future payments it may make in its role as a vendor (i.e., Amicus) to its customer (i.e., GSK) and evaluated if these potential future payments could be a reduction of revenue from GSK. If the potential future payments to GSK are as follows:


	•	a payment for an identifiable benefit, and
	•	the identifiable benefit is separable from the existing relationship between the Company and GSK, and
	•	the identifiable benefit can be obtained from a party other than GSK, and
	•	the Company can reasonably estimate the fair value of the identifiable benefit,

then the potential future payments would be treated separately from the collaboration and research revenue. However, if all these criteria are not satisfied, then the potential future payments are treated as a reduction of revenue.

Accordingly, the Company did not believe that, for accounting purposes, the new U.S. licensing rights to migalastat obtained from GSK under the Expanded Collaboration Agreement, nor the ex U.S. licensing rights to migalastat obtained from GSK under the Revised Agreement, represented a separate, identifiable benefit from the licenses in the Original Collaboration Agreement entered into between Amicus and GSK in 2010. The contingent amounts payable to GSK were not sufficiently separable from GSK's original license and the research and development reimbursements such that Amicus could not have entered into a similar exchange transaction with another party. Additionally, the Company cannot reasonably estimate the fair value of the worldwide licensing rights to migalastat.

The Company determined that the potential future payments to GSK would be treated as a reduction of revenue and that the total amount of revenue to be received under the arrangement is no longer fixed or determinable as the contingent milestone payments are subject to significant uncertainty.

As a result, the Company no longer recognized any of the upfront license fees and premiums on the equity purchase from GSK until such time as the arrangement consideration becomes fixed or determinable, because an indeterminable amount may ultimately be payable back to GSK. These amounts (the balance of the unrecognized upfront license fee and the premium on the equity purchases) are classified as deferred reimbursements on the balance sheet. As of December 31, 2017, the Company recognized a liability of $21.9 million as deferred reimbursements, in addition to $1.3 million related to milestone payable to GSK in accounts payable, accrued expenses, and other current liabilities in the Consolidated Balance Sheets.

The recognition of Research Revenue was also affected by the determination that the overall total arrangement consideration was no longer fixed and determinable, despite the fact that the research activities continued and that the research expense reimbursements by GSK to Amicus were received as the research activities related to the reimbursement had been completed. Therefore the research reimbursements from GSK were recorded as deferred reimbursements on the balance sheet and would not recognized until the total arrangement consideration becomes fixed and determinable.

As a result, all revenue recognition was suspended until the total arrangement consideration would become fixed and determinable. In addition, future milestone payments made by the Company will be applied against the balance of this deferred reimbursements account. Revenue recognition for research expense reimbursements, the original upfront license fee, and the equity premiums will resume once the total arrangement consideration becomes fixed and determinable which will occur when the balance of the deferred reimbursements account is sufficient to cover all the remaining contingent milestone payments.

Earnings per Share

12 Months Ended

Dec. 31, 2017

Earnings per Share

Earnings per Share

16. Earnings per Share

The following table provides a reconciliation of the numerator and denominator used in computing basic and diluted net loss attributable to common stockholders per common share (in thousands except share amounts):

	Years Ended December 31,
Historical	2017			2016			2015
Numerator:
Net loss attributable to common stockholders	$	(284,002	)	$	(200,042	)	$	(132,118	)


Denominator:
Weighted average common shares outstanding — basic and diluted		153,355,144			134,401,588			109,923,815

Dilutive common stock equivalents would include the dilutive effect of common stock options, convertible debt units, RSUs and warrants for common stock equivalents. Potentially dilutive common stock equivalents were excluded from the diluted earnings per share denominator for all periods because of their anti-dilutive effect. For the year ended 2017 there was 40.9 million potential common shares outstanding as a result of the convertible debt that was excluded from the diluted net loss per share calculation because their effect would have been anti-dilutive.

The table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method (in thousands):

	Year ended December 31,
	2017		2016		2015
Options to purchase common stock		15,181		15,528		11,729
Convertible debt		40,850		40,850		—
Outstanding warrants, convertible to common stock		3,110		3,110		1,350
Unvested restricted stock units		2,575		744		479
Vested restricted stock units, unissued		50		—		—

Total number of potentially issuable shares		61,766		60,232		13,558

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2017
Commitments and Contingencies
Commitments and Contingencies	17. Commitments and Contingencies Since October 1, 2015, three purported securities class action lawsuits were filed in the United States District Court for New Jersey, naming as defendants the Company, its Chairman and Chief Executive Officer, and in one of the actions, its Chief Medical Officer. The lawsuits alleged violations of the Securities Exchange Act of 1934 in connection with allegedly false and misleading statements made by the Company related to the regulatory approval path for migalastat. The plaintiffs sought, among other things, damages for purchasers of the Company's Common Stock during different periods, all of which fall between March 19, 2015 and October 1, 2015. On May 26, 2016, the Court consolidated these lawsuits into a single action entitled In re Amicus Therapeutics, Inc. Shareholder Litigation (C.A. # 3:15-cv-07350) and appointed a lead plaintiff. The lead plaintiff filed a Consolidated Amended Class Action Complaint on July 11, 2016. On August 25, 2016, the Company and other defendants filed a motion to dismiss in response to the Consolidated Amended Class Action Complaint. This motion to dismiss was fully briefed on October 28, 2016. Before the motion was decided, the lead plaintiff and defendants entered into a Stipulation and Agreement of Settlement dated April 14, 2017. Thereafter, on June 29, 2017, the Court entered an order granting preliminary approval of the Settlement. On November 9, 2017, the Court conducted a fairness hearing and on November 15, 2017, entered an Order and Final Judgment approving the Settlement. Among other provisions, the Settlement provides defendants with a release of all claims and involves the creation of a Settlement Fund for class members in the amount of $3.8 million. The majority of the amount was covered under insurance and any out of pocket expenses were immaterial to the Company's consolidated financial statements. On or about March 3, 2016, a derivative lawsuit was filed by an Amicus shareholder purportedly on Amicus' behalf in the Superior Court of New Jersey, Middlesex County, Chancery Division, against various officers and directors of the Company. Amicus itself is named as a nominal defendant. The derivative lawsuit alleges similar facts and circumstances as the three purported securities class action lawsuits described above and further alleges claims for breach of state law fiduciary duties, waste of corporate assets, unjust enrichment, abuse of control, and gross mismanagement based on allegedly false and misleading statements made by Amicus related to the regulatory approval path for migalastat HCl. The plaintiff seeks, among other things, to require the Amicus Board to take certain actions to reform its corporate governance procedures, including greater shareholder input and a provision to permit shareholders to nominate candidates for election to the Board, along with restitution, costs of suit and attorney's fees. On February 7, 2017, the complaint was dismissed by the Court without prejudice. These lawsuits and any other related lawsuits are subject to inherent uncertainties and the actual cost will depend upon many unknown factors. The outcome of any litigation is necessarily uncertain and we could be forced to expend significant resources in the defense of these lawsuits, and we may not prevail.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events
Subsequent Events	18. Subsequent Events On February 15, 2018, the Company announced the pricing of an underwritten offering of 19,354,839 shares of its common stock at $15.50 per shares, resulting in gross proceeds of $300.0 million, before deducting underwriting discounts and commissions and offering expenses payable by the Company. The offering closed on February 21, 2018 and the Company received net proceeds of $282.0 million from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by the Company. J.P. Morgan Securities LLC and Goldman Sachs & Co. LLC were acting as joint lead book-running managers, Cowen and Leerink Partners were acting as co-book-running managers, and BofA Merrill Lynch was acting as lead co-manager for the offering. The Company expects to use the net proceeds of the offering for investment in the U.S. and international commercial infrastructure for migalastat HCl, investment in manufacturing capabilities for ATB200, the continued clinical development of its product candidates, research and development expenditures, clinical and pre-clinical trial expenditures, commercialization expenditures and for other general corporate purposes. The securities described above are being offered by the Company pursuant to a registration statement previously filed with the U.S. Securities and Exchange Commission (the "SEC") on April 29, 2016, which became effective automatically upon the filing thereof.

Selected Quarterly Financial Data (Unaudited - in thousands except per share data)

12 Months Ended

Dec. 31, 2017

Selected Quarterly Financial Data (Unaudited - in thousands except per share data)

Selected Quarterly Financial Data (Unaudited - in thousands except per share data)

19. Selected Quarterly Financial Data (Unaudited — in thousands except per share data)

	Quarters Ended
	March 31			June 30			September 30			December 31
2017
Net loss	$	(54,992	)	$	(48,136	)	$	(111,666	)	$	(69,208	)
Basic and diluted net loss per common share (1)	$	(0.39	)	$	(0.34	)	$	(0.69	)	$	(0.42	)
2016
Net loss	$	(43,691	)	$	(51,050	)	$	(46,654	)	$	(58,647	)
Basic and diluted net loss per common share (1)		(0.35	)		(0.40	)		(0.33	)		(0.41	)


(1)	Per common share amounts for the quarters and full years have been calculated separately. Accordingly, quarterly amounts do not add to the annual amounts because of differences on the weighted-average common shares outstanding during each period principally due to the effect of the Company issuing shares of its common stock during the year.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") and include all adjustments necessary for the fair presentation of the Company's financial position for the periods presented.
Consolidation	Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany accounts and transactions are eliminated in consolidation.
Foreign Currency Transactions	Foreign Currency Transactions The functional currency for most of the Company's foreign subsidiaries is their local currency. For non-U.S. subsidiaries that transact in a functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of the Company's foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of equity.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Cash, Money Market Funds, and Marketable Securities	Cash, Money Market Funds, and Marketable Securities The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of acquisition, to be cash equivalents. Marketable securities consist of fixed income investments with a maturity of greater than three months and other highly liquid investments that can be readily purchased or sold using established markets. These investments are classified as available-for-sale and are reported at fair value on the Company's balance sheet. Unrealized holding gains and losses are reported within comprehensive income/ (loss) in the statements of comprehensive loss. Fair value is based on available market information including quoted market prices, broker or dealer quotations or other observable inputs. See "— Note 5. Cash, Money Market Funds and Marketable Securities", for a summary of available-for-sale securities as of December 31, 2017 and 2016.
Concentration of Credit Risk	Concentration of Credit Risk The Company's financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and marketable securities. The Company maintains its cash and cash equivalents in bank accounts, which, at times, exceed federally insured limits. The Company invests its marketable securities in high-quality commercial financial instruments. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on cash and cash equivalents or its marketable securities. The Company is subject to credit risk from its accounts receivable related to its product sales of GALAFOLD. The Company's accounts receivable at December 31, 2017 have arisen from product sales in the EU. The Company will periodically assess the financial strength of its customers to establish allowances for anticipated losses, if any. For accounts receivable that have arisen from named patient sales, the payment terms are predetermined and the Company evaluates the creditworthiness of each customer on a regular basis. To date, the Company has not incurred any credit losses.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated over the estimated useful lives of the respective assets, which range from three to five years, or the lesser of the related initial term of the lease or useful life for leasehold improvements. The initial cost of property and equipment consists of its purchase price and any directly attributable costs of bringing the asset to its working condition and location for its intended use. Expenditures incurred after the fixed assets have been put into operation, such as repairs and maintenance, are charged to income in the period in which the costs are incurred. Major replacements, improvements and additions are capitalized in accordance with Company policy.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when amounts are realized or realizable and earned, which is typically upon receipt by the customer. Revenue is considered realizable and earned when persuasive evidence an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collection of the amounts due are reasonably assured and the Company has no further performance obligations. Net Product Sales The Company's net product sales consist solely of sales of GALAFOLD for the treatment of Fabry disease in the EU. The Company has recorded revenue on sales where GALAFOLD is available either on a commercial basis or through a reimbursed early access program. Orders for GALAFOLD are generally received from pharmacies and the ultimate payor is typically a government authority. The Company records revenue net of estimated third party discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. These allowances are adjusted to reflect known changes in factors and may impact such allowances in the quarter those changes are known.
Inventories and Cost of Goods Sold	Inventories and Cost of Goods Sold Prior to regulatory approval of GALAFOLD, the Company expensed all manufacturing costs related to GALAFOLD as research and development expense. Upon regulatory approval, the Company began capitalizing costs related to the purchase and manufacture of GALAFOLD. Inventories are stated at the lower of cost and net realizable value, determined by the first-in, first-out method. Inventories are reviewed periodically to identify slow-moving or obsolete inventory based on projected sales activity as well as product shelf-life. In evaluating the recoverability of inventories produced, the probability that revenue will be obtained from the future sale of the related inventory is considered and inventory value is written down for inventory quantities in excess of expected requirements. Expired inventory is disposed of and the related costs are recognized as cost of product sales in the consolidated statements of operations. Cost of goods sold includes the cost of inventory sold, manufacturing and supply chain costs, product shipping and handling costs, provisions for excess and obsolete inventory, as well as royalties payable. A portion of the inventory available for sale was expensed as research and development costs prior to regulatory approval and as such the cost of goods sold and related gross margins are not necessarily indicative of future cost of goods sold and gross margin.
Fair Value Measurements	Fair Value Measurements The Company records certain asset and liability balances under the fair value measurements as defined by the FASB guidance. Current FASB fair value guidance emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, current FASB guidance establishes a fair value hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity's own assumptions that market participants assumptions would use in pricing assets or liabilities (unobservable inputs classified within Level 3 of the hierarchy). Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at measurement date. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity's own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company's assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability.
Contingent Liabilities	Contingent Liabilities On an ongoing basis, the Company may be involved in various claims, and legal proceedings. On a quarterly basis, the Company reviews the status of each significant matter and assesses its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, the Company will accrue a liability for the estimated loss. Because of uncertainties related to claims and litigation, accruals will be based on the Company's best estimates based on available information. On a periodic basis, as additional information becomes available, or based on specific events such as the outcome of litigation or settlement of claims, the Company may reassess the potential liability related to these matters and may revise these estimates, which could result in material adverse adjustments to the Company's operating results.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expense consists primarily of costs related to personnel, including salaries and other personnel related expenses, consulting fees and the cost of facilities and support services used in drug development. Assets acquired that are used for research and development and have no future alternative use are expensed as in-process research and development.
Interest Income and Interest Expense	Interest Income and Interest Expense Interest income consists of interest earned on the Company's cash and cash equivalents and marketable securities. Interest expense consists of interest incurred on debt and capital leases.
Income Taxes	Income Taxes The Company accounts for income taxes under the liability method. Under this method deferred income tax liabilities and assets are determined based on the difference between the financial statement carrying amounts and tax basis of assets and liabilities and for operating losses and tax credit carry forwards, using enacted tax rates in effect in the years in which the differences are expected to reverse. A valuation allowance is recorded if it is "more likely than not" that a portion or all of a deferred tax asset will not be realized.
Other Comprehensive Income/ (Loss)	Other Comprehensive Income/ (Loss) Components of other comprehensive income/ (loss) include unrealized gains and losses on available-for-sale securities and gain/ (loss) on foreign currency transactions, and are included in the statements of comprehensive loss.
Leases	Leases In the ordinary course of business, the Company enters into lease agreements for office space as well as leases for certain property and equipment. The leases have varying terms and expirations and have provisions to extend or renew the lease agreement, among other terms and conditions, as negotiated. Once the agreement is executed, the lease is assessed to determine whether the lease qualifies as a capital or operating lease. When a non-cancelable operating lease includes any fixed escalation clauses and lease incentives for rent holidays or build-out contributions, rent expense is recognized on a straight-line basis over the initial term of the lease. The excess between the average rental amount charged to expense and amounts payable under the lease is recorded in accrued expenses.
Nonqualified Cash Deferral Plan	Nonqualified Cash Deferral Plan The Company's Cash Deferral Plan (the "Deferral Plan"), provides certain key employees and members of the Board of Directors as selected by the Compensation Committee of the Board of Directors of the Company (the "Compensation Committee"), with an opportunity to defer the receipt of such participant's base salary, bonus and director's fees, as applicable. The Deferral Plan is intended to be a nonqualified deferred compensation plan that complies with the provisions of Section 409A of the Internal Revenue Code (the "Code"). All of the investments held in the Deferral Plan are classified as investments held-to-maturity and recorded at fair value with changes in the investments' fair value recognized as earnings in the period they occur. The corresponding liability for the Deferral Plan is included in other non-current liability in the consolidated balance sheets.
Equity- based Compensation	Equity-based Compensation At December 31, 2017, the Company had three equity-based employee compensation plans, which are described more fully in "— Note 9. Stockholders' Equity." The Company applies the fair value method of measuring equity-based compensation, which requires a public entity to measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award.
Loss per Common Share	Loss per Common Share The Company calculates net loss per share as a measurement of the Company's performance while giving effect to all dilutive potential common shares that were outstanding during the reporting period. The Company had a net loss for all periods presented; accordingly, the inclusion of common stock options, unvested RSUs and warrants would be anti-dilutive. Therefore, the weighted average shares used to calculate both basic and diluted earnings per share are the same. See "— Note 17. Earnings per Share" for further discussion on net loss per share.
Segment Information	Segment Information The Company currently operates in one business segment focused on the discovery, development and commercialization of advanced therapies to treat a range of devastating rare and orphan diseases. The Company is not organized by market and is managed and operated as one business. A single management team reports to the chief operating decision maker who comprehensively manages the entire business. The Company does not operate any separate lines of business or separate business entities with respect to its products. Accordingly, the Company does not accumulate discrete financial information with respect to separate service lines and does not have separately reportable segments.
Business Combinations	Business Combinations The Company assigns fair value to the tangible and intangible assets acquired and liabilities assumed based upon their estimated fair values on the acquisition date from acquired businesses. The purchase price allocation process requires management to make significant estimates and assumptions, especially at the acquisition date with respect to intangible assets and in-process research and development ("IPR&D"). In connection with the purchase price allocations for acquisitions, the Company estimates the fair value of contingent payments utilizing a probability-based income approach inclusive of an estimated discount rate.
Contingent Consideration Payable	Contingent Consideration Payable The Company determines the fair value of contingent acquisition consideration payable on the acquisition date using a probability-based income approach utilizing an appropriate discount rate. Contingent acquisition consideration payable is shown as a non-current liability on the Company's consolidated balance sheets. The fair value of the contingent consideration payable will be determined each period end and the resulting change will be recorded on the consolidated statements of operations.
Intangible Assets and Goodwill	Intangible Assets and Goodwill The Company records goodwill in a business combination when the total consideration exceeds the fair value of the net tangible and identifiable intangible assets acquired. Purchased IPR&D is accounted for as an indefinite lived intangible asset until the underlying project is completed, at which point the intangible asset will be accounted for as a definite lived intangible asset, or abandoned, at which point the intangible asset will be written off or partially impaired. Goodwill and indefinite lived intangible assets are assessed annually for impairment and whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. If it is determined that the full carrying amount of an asset is not recoverable, an impairment loss is recorded in the amount by which the carrying amount of the asset exceeds its fair value.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendments in this Update better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. To meet that objective, the amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in this Update also make certain targeted improvements to simplify the application of hedge accounting guidance and ease the administrative burden of hedge documentation requirements and assessing hedge effectiveness. For public business entities, the amendment is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption, including adoption in an interim period, is permitted. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception. Part I of this Update addresses the complexity of accounting for certain financial instruments with down round features. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced on the basis of the pricing of future equity offerings. When determining whether certain financial instruments should be classified as liabilities or equity instruments, a down round feature no longer precludes equity classification when assessing whether the instrument is indexed to an entity's own stock. Part II of this Update addresses the difficulty of navigating Topic 480, Distinguishing Liabilities from Equity, because of the existence of extensive pending content in the FASB Accounting Standards Codification®. For public business entities, the amendments in Part I of this Update are effective for fiscal years, and years, beginning after December 15, 2018. Early adoption is permitted for all entities, including adoption in an interim period. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting. The amendments provide guidance on determining which changes to the terms and conditions of share-based payment awards require an entity to apply modification accounting under Topic 718 Compensation — Stock Compensation. An entity should account for the effects of a modification unless all the following are met: 1. The fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the modified award is the same as the fair value (or calculated value or intrinsic value, if such an alternative measurement method is used) of the original award immediately before the original award is modified. If the modification does not affect any of the inputs to the valuation technique that the entity uses to value the award, the entity is not required to estimate the value immediately before and after the modification. 2. The vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified. 3. The classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The ASU is effective for all entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, including adoption in any interim period. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables — Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. The amendments shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The ASU is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. For other entities, the amendments are effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles — Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. To simplify the subsequent measurement of goodwill, ASU 2017-04 eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. ASU 2017-04 also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 should be applied on a prospective basis. The nature of and reason for the change in accounting principle should be disclosed upon transition. A public business entity that is a U.S. SEC filer should adopt ASU 2017-04 for its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. This Accounting Standards Update clarifies the definition of a business. The amendments affect all companies and other reporting organizations that must determine whether they have acquired or sold a business. The amendments in this Update are effective for public companies for annual periods beginning after December 15, 2017, including interim periods within those periods. Early adoption is permitted under certain circumstances. The amendments should be applied prospectively as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. This Accounting Standards Update requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The amendments eliminate the exception for an intra-entity transfer of an asset other than inventory. The amendments in this Update are effective for public business entities for annual periods beginning after December 15, 2017, including interim reporting periods within those annual reporting periods. Early adoption is permitted for all entities in the first interim period if an entity issues interim financial statements. The Company is currently assessing the impact that this standard will have on its consolidated financial statements and plans to adopt this ASU in the first quarter of 2018 using a modified retrospective approach with any adjustment, if any, to be recorded in retained earnings as January 1, 2018. The Company is completing the assessment of the impact, if any, of the adoption of this standard. In March 2016, the FASB issued ASU 2016-09, Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The amendments are intended to improve the accounting for employee share-based payments and affect all organizations that issue share-based payment awards to their employees. Several aspects of the accounting for share-based payment award transactions are simplified, including: (a) income tax consequences; (b) classification of awards as either equity or liabilities; and (c) classification on the statement of cash flows. For public companies, the amendments are effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted for any organization in any interim or annual period. The Company adopted ASU 2016-09 on January 1, 2017. The adoption resulted in an increase to the Company's NOL and valuation allowance by $4.0 million, however there was no impact on Retained earnings and the classification of excess tax benefits on the statement of cash flows for prior periods have not been adjusted. In connection with the adoption of ASU 2016-9, the Company has decided to continue its current policy and estimate forfeitures and adjust the estimate when it is likely to change. This election will have no impact on the Company's consolidated financial statements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This update requires the recognition of lease assets and lease liabilities on the balance sheet for all lease obligations and disclosing key information about leasing arrangements. This update requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous generally accepted accounting principles. This update will be effective for the Company for all annual and interim periods beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted for all public business entities and all nonpublic business entities upon issuance. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, "Financial Instruments — Overall: Recognition and Measurement of Financial Assets and Financial Liabilities" (ASU 2016-01). ASU 2016-01 changes accounting for equity investments, financial liabilities under the fair value option, and presentation and disclosure requirements for financial instruments. ASU 2016-01 does not apply to equity investments in consolidated subsidiaries or those accounted for under the equity method of accounting. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. Equity investments with readily determinable fair values will be measured at fair value with changes in fair value recognized in net income. Companies have the option to either measure equity investments without readily determinable fair values at fair value or at cost adjusted for changes in observable prices minus impairment. Companies that elect the fair value option for financial liabilities must recognize changes in fair value related to instrument-specific credit risk in other comprehensive income. Companies must assess valuation allowances for deferred tax assets related to available-for-sale debt securities in combination with their other deferred tax assets. ASU 2016-01 will be effective beginning in the first quarter of 2018. We will adopt this ASU in the first quarter of 2018. We expect the implementation of this standard to have no impact on our Consolidated Financial Statements and related disclosures, as the Company does not have equity investments and liabilities with credit risk and the guidance relating to deferred tax assets is currently in place at Amicus even prior to the adoption of the ASU. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes. ASU 2015-17 requiring companies to classify all deferred tax assets and liabilities as noncurrent on the balance sheet instead of separating deferred taxes into current and noncurrent amounts. For public business entities, the guidance is effective for financial statements issued for annual periods beginning after 15 December 2016, and interim periods within those annual periods. The Company adopted this guidance as of January 1, 2017 and the adoption did not have a material impact on its consolidated financial statements. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which requires an entity to measure in scope inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendments apply to inventory that is measured using first-in, first-out (FIFO) or average cost. The ASU is effective for public business entities for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. A reporting entity should apply the amendments prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company adopted this guidance as of January 1, 2017 and the adoption did not have any impact on its consolidated financial statements. In May 2014, FASB issued ASU 2014-09, Revenue from Contracts with Customers which along with amendments issued in 2015 and 2016, will replace substantially all current US GAAP guidance on this topic and eliminate industry-specific guidance. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance permits two methods of adoption: full retrospective method (retrospective application to each prior reporting period presented) or modified retrospective method (retrospective application with the cumulative effect of initially applying the guidance recognized at the date of initial application and providing certain additional disclosures). The Company has elected to adopt the new standard using the modified retrospective approach. ASU 2014-09 is effective for the Company during the first quarter of 2018. The Company's implementation plan included a phased project plan, an understanding of the new standard and its requirements, assessment of the Company's revenue streams and specific contracts in the streams. Additionally, the Company continues to monitor modifications, clarifications and interpretations issued by the FASB that may impact its assessment. While the Company performed a detailed review of representative contracts and assessed the potential impacts the standard may have on previously reported revenues and future revenues, the Company is finalizing its assessment of the adoption of the new standard. Based on the adoption of the ASU 2014-09, the Company identified two revenue streams: sales to distributors and pharmacies. The timing of revenue recognition and treatment of contract costs remains unchanged under the new standard. As such, the Company does not expect the adoption of ASU 2014-09 to have a material impact on its consolidated financial statements. The Company does expect the adoption of the new standard to impact its financial reporting disclosures and internal controls over financial reporting. The Company has developed implementation controls that allow the Company to properly and timely adopt the new revenue accounting standard on its effective date.

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets

Schedule of changes in IPR&D

	(in millions)
Balance at December 31, 2016	$	486.7
Impairment in IPR&D related to Scioderm		(463.7	)

Balance at December 31, 2017	$	23.0

Schedule of changes in goodwill

	(in millions)
Balance at December 31, 2016	$	197.8
Change in goodwill		—

Balance at December 31, 2017	$	197.8

Cash, Money Market Funds and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Cash, Money Market Funds and Marketable Securities

Schedule of cash and available for sale securities

Cash and available for sale securities consisted of the following as of December 31, 2017 and December 31, 2016 (in thousands):

	As of December 31, 2017
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	49,060	$	—	$	—		$	49,060
Corporate debt securities, current portion		199,314		1		(303	)		199,012
Commercial paper		79,878		—		(75	)		79,803
Asset-backed securities		30,346		—		(59	)		30,287
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	358,998	$	1	$	(437	)	$	358,562


Included in cash and cash equivalents	$	49,060	$	—	$	—		$	49,060
Included in marketable securities		309,938		1		(437	)		309,502

Total cash and marketable securities	$	358,998	$	1	$	(437	)	$	358,562

	As of December 31, 2016
	Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash balances	$	187,026	$	—	$	—		$	187,026
Corporate debt securities, current portion		74,564		2		(31	)		74,535
Commercial paper		68,258		132		—			68,390
Money market		350		—		—			350
Certificate of deposit		50		—		—			50

	$	330,248	$	134	$	(31	)	$	330,351


Included in cash and cash equivalents	$	187,026	$	—	$	—		$	187,026
Included in marketable securities		143,222		134		(31	)		143,325

Total cash and marketable securities	$	330,248	$	134	$	(31	)	$	330,351

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventories

Schedule of inventories for the period

The following table summarizes the components of inventories at December 31, 2017 (in thousands):

	December 31, 2017		December 31, 2016
Work-in-process	$	3,843	$	3,308
Finished goods		780		108

Total inventories	$	4,623	$	3,416

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property and Equipment

Schedule of property and equipment

Property and equipment consist of the following (in thousands):

	December 31,
	2017			2016
Property and equipment consist of the following:
Computer equipment	$	3,746		$	3,511
Computer software		1,236			1,347
Research equipment		6,379			7,465
Furniture and fixtures		2,992			3,018
Leasehold improvements		7,193			6,970
Construction in progress		31			—

		21,577			22,311
Less accumulated depreciation		(12,515	)		(12,495	)

	$	9,062		$	9,816

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Accounts Payable and Accrued Expenses

Schedule of accounts payable and accrued expenses

Accounts payable and accrued expenses consist of the following (in thousands):

	December 31,
	2017		2016
Accounts payable	$	7,867	$	12,905
Accrued professional fees		5,845		5,079
Accrued contract manufacturing & contract research costs		4,632		8,042
Accrued compensation and benefits		19,620		9,686
Accrued facility costs		1,665		1,740
Accrued program fees		5,707		—
Foreign currency forward contract		—		265
Capital lease, short term portion		307		283
Royalties payable		2,529		510
Accrued interest		313		208
Accrued other		5,405		2,290

	$	53,890	$	41,008

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Stockholders' Equity

Summary of deferred compensation amounts

The following table summarizes the deferred compensation amounts under the Deferral Plan as of December 31, 2017 and 2016, respectively (in thousands):

	Year ended December 31,
	2017		2016
Deferred compensation investment	$	2,248	$	1,469
Deferred compensation liability	$	2,258	$	1,479
Investment income	$	66	$	34
Unrealized gain	$	92	$	32

Schedule of fair value weighted-average assumptions

	Years Ended December 31,
	2017			2016			2015
Expected stock price volatility		82.8	%		81.3	%		75.9	%
Risk free interest rate		2.0	%		1.5	%		1.7	%
Expected life of options (years)		6.18			6.25			6.25
Expected annual dividend per share	$	0.00		$	0.00		$	0.00

Summary of stock options outstanding

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
	(in thousands)						(in millions)
Options outstanding, December 31, 2014		10,020.7		$	5.02
Granted		3,917.2		$	11.61
Exercised		(2,070.3	)	$	5.43
Forfeited		(138.4	)	$	7.76

Options outstanding, December 31, 2015		11,729.2		$	7.11
Granted		5,114.1		$	7.67
Exercised		(723.1	)	$	4.20
Forfeited		(622.7	)	$	8.62

Options outstanding, December 31, 2016		15,497.5		$	7.37
Granted		3,695.3		$	7.17
Exercised		(2,878.7	)	$	5.67
Forfeited		(1,133.0	)	$	9.55

Options outstanding, December 31, 2017		15,181.1		$	7.48	7.2 years	$	105.8


Vested and unvested expected to vest, December 31, 2017		14,398.5		$	7.45	7.1 years	$	100.9
Exercisable at December 31, 2017		7,985.6		$	7.05	6.0 years	$	59.1

Summary of non-vested Restricted Stock Units activity

	Number of Share			Weighted Average Grant Date Fair Value		Weighted Average Remaining Years		Aggregate Intrinsic Value
	(in thousands)							(in millions)
Non-vested units as of December 31, 2015		478.5		$	10.38
Granted		582.7		$	6.21
Vested		(281.9	)	$	8.73
Forfeited		(34.9	)	$	7.71

Non-vested units as of December 31, 2016		744.4		$	7.86
Granted		2,348.7		$	5.69
Vested		(318.2	)	$	9.23
Forfeited		(199.8	)	$	6.24

Non-vested units as of December 31, 2017		2,575.1		$	5.85		2.47	$	37.1

Summary of the equity-based compensation expense recognized in the statements of operations

The following table summarizes the equity-based compensation expense recognized in the statements of operations (in thousands):

	Years Ended December 31,
	2017		2016		2015
Equity compensation expense recognized in:
Research and development expense	$	10,328	$	8,071	$	4,600
Selling, general and administrative expense		12,773		9,433		5,372

Total equity compensation expense	$	23,101	$	17,504	$	9,972

Assets and Liabilities Measured at Fair Value (Tables)

12 Months Ended

Dec. 31, 2017

Financial assets and liabilities subject to fair value measurements

Summary of assets and liabilities subject to fair value measurements

	Level 2		Total
Assets:
Commercial paper	$	79,803	$	79,803
Asset-back securities		30,287		30,287
Corporate debt securities		199,012		199,012
Money market funds		2,598		2,598

	$	311,700	$	311,700

	Level 2		Level 3		Total
Liabilities:
Contingent consideration payable	$	—	$	25,400	$	25,400
Deferred compensation plan liability		2,258		—		2,258

	$	2,258	$	25,400	$	27,658

	Level 2		Total
Assets:
Commercial paper	$	68,390	$	68,390
Corporate debt securities		74,535		74,535
Money market funds		1,829		1,829

	$	144,754	$	144,754

	Level 2		Level 3		Total
Liabilities:
Contingent consideration payable	$	—	$	269,722	$	269,722
Derivative liability		265		—		265
Deferred compensation plan liability		1,479		—		1,479

	$	1,744	$	269,722	$	271,466

Schedule of changes in contingent consideration payable

The following table shows the change in the balance of contingent consideration payable for the year ended December 31, 2017 and 2016, respectively (in thousands):

	Year ended December 31,
	2017			2016
Balance, beginning of the period	$	269,722		$	274,077
Payment of contingent consideration in cash		(10,000	)		(5,000	)
Payment of contingent consideration in stock		—			(6,115	)
Unrealized change in fair value change during the period, included in Statement of Operations		(234,322	)		6,760

Balance, end of the period	$	25,400		$	269,722

Callidus

Financial assets and liabilities subject to fair value measurements

Schedule of significant unobservable inputs used in the valuation of the contingent consideration payable

Contingent Consideration Liability	Fair value as of December 31, 2017	Valuation Technique	Unobservable Input	Range
			Discount rate	11.5%
Clinical and regulatory milestones	$25.0 million	Probability weighted discounted cash flow	Probability of achievement of milestones	71.0% - 100.0%
			Projected year of payments	2018 - 2022

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Debt Instruments and Related Party Transactions (Tables)

12 Months Ended

Dec. 31, 2017

Debt Instruments and Related Party Transactions

Schedule of liability components of the Convertible Notes

The Convertible Notes consist of the following as of December 31, 2017 and 2016 (In thousands):

Liability component	2017			2016
Principal	$	250,000		$	250,000
Less: debt discount (1)		(81,566	)		(90,807	)
Less: deferred financing (1)		(4,267	)		(4,729	)

Net carrying value of the debt	$	164,167		$	154,464


(1)	Included in the Consolidated Balance Sheets within Convertible Senior Notes (due 2023) and amortized to interest expense over the remaining life of the Convertible Senior Notes using the effective interest rate method.

Components of total interest expense recognized related to the Convertible Notes

The following table sets forth total interest expense recognized related to the Convertible Notes for the year ended December 31, 2017 and 2016 (In thousands):

Components	2017			2016
Contractual interest expense	$	7,528		$	208
Amortization of deferred financing		470			26
Amortization of debt discount		9,241			248

Total	$	17,239		$	482


Effective interest rate of the liability component		10.85	%		10.85	%

Leases (Tables)

12 Months Ended

Dec. 31, 2017

Leases

Schedule of current significant leased properties

The following table contains information about our current significant leased properties as of December 31, 2017:

Location	Approximate Square Feet		Use	Lease expiry date
Cranbury, New Jersey		90,000	Office and laboratory	September 2025
Durham, North Carolina		5,603	Office	June 2018
Buckinghamshire, United Kingdom		9,821	Office	September 2020
Munich, Germany		4,751	Office	April 2022

Schedule of aggregate annual future minimum lease payments under the operating leases

At December 31, 2017, aggregate annual future minimum lease payments under these leases are as follows:

(in thousands)		2018			2019			2020			2021			2022 and beyond			Total
Minimum lease payments		$	2,762		$	2,575		$	2,472		$	2,240		$	8,467		$	18,516

Schedule of aggregate annual future minimum lease payments under the capital leases, including interest

At December 31, 2017, aggregate annual future minimum lease payments under these leases, including interest, are as follows (in thousands):

Years ending December 31:
2018	$	356
2019		134
2020		—
2021		—
2022 and beyond		—

Total principal obligation	$	490

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of income (loss) before income taxes

For financial reporting purposes, income (loss) before income taxes includes the following components (in thousands):

	Years Ended December 31,
	2017			2016			2015
United States	$	(440,696	)	$	(174,913	)	$	(123,697	)
Foreign		(8,425	)		(28,868	)		(8,421	)

Total	$	(449,121	)	$	(203,781	)	$	(132,118	)

Schedule of income tax expense (benefit)

Following were the components of income tax expense (benefit) for the years ending December 31, 2017 and December 31, 2016:

	2017			2016			2015
Current:
State	$	9		$	7		$	—
Foreign		2,276			—			—
Deferred
Federal		(150,015	)		(1,101	)		—
State		(17,389	)		(2,645	)		—

Total	$	(165,119	)	$	(3,739	)	$	—

Schedule of reconciliation of the statutory tax rates and the effective tax rates

	Years Ended December 31,
	2017			2016			2015
Statutory rate		(34	)%		(34	)%		(34	)%
State taxes, net of federal benefit		(5	)		(5	)		(5	)
Permanent adjustments		(1	)		3			2
Contingent consideration		(18	)		—			—
R&D credit		(2	)		(3	)		(3	)
Foreign income tax rate differential		5			2			1
Impact of 2017 Act		27			—			—
Other		5			(1	)		2
Valuation allowance		(14	)		36			37

Net		(37	)%		(2	)%		(0	)%

Schedule of significant components of the deferred tax assets and liabilities

The significant components of the deferred tax assets and liabilities are as follows (in thousands):

	For Years Ended December 31,
	2017			2016
Deferred tax assets
Intellectual property	$	44,573		$	95,956
Amortization/depreciation		3,082			1,781
Research tax credit		43,382			32,851
Net operating loss carry forwards		221,912			223,758
Deferred revenue		6,158			14,281
Non-cash stock issue		10,751			11,649
Others		7,328			3,358

Gross deferred tax assets		337,186			383,634
Deferred tax liabilities
Business acquisition		(6,465	)		(173,771	)
Royalty payable		(44,573	)		(96,829	)
Convertible notes		(18,991	)		(29,845	)
Advanced R&D payments		(3,069	)		—

Total net deferred tax asset		264,088			83,189
Less valuation allowance		(270,553	)		(256,960	)

Net deferred tax liability	$	(6,465	)	$	(173,771	)

Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings per Share

Schedule of reconciliation of the numerator and denominator used in computing basic and diluted net loss per common share

	Years Ended December 31,
Historical	2017			2016			2015
Numerator:
Net loss attributable to common stockholders	$	(284,002	)	$	(200,042	)	$	(132,118	)


Denominator:
Weighted average common shares outstanding — basic and diluted		153,355,144			134,401,588			109,923,815

Schedule of potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method

The table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method (in thousands):

	Year ended December 31,
	2017		2016		2015
Options to purchase common stock		15,181		15,528		11,729
Convertible debt		40,850		40,850		—
Outstanding warrants, convertible to common stock		3,110		3,110		1,350
Unvested restricted stock units		2,575		744		479
Vested restricted stock units, unissued		50		—		—

Total number of potentially issuable shares		61,766		60,232		13,558

Selected Quarterly Financial Data (Unaudited - in thousands except per share data) (Tables)

12 Months Ended

Dec. 31, 2017

Selected Quarterly Financial Data (Unaudited - in thousands except per share data)

Schedule of selected quarterly financial data

Selected Quarterly Financial Data (Unaudited — in thousands except per share data)

	Quarters Ended
	March 31			June 30			September 30			December 31
2017
Net loss	$	(54,992	)	$	(48,136	)	$	(111,666	)	$	(69,208	)
Basic and diluted net loss per common share (1)	$	(0.39	)	$	(0.34	)	$	(0.69	)	$	(0.42	)
2016
Net loss	$	(43,691	)	$	(51,050	)	$	(46,654	)	$	(58,647	)
Basic and diluted net loss per common share (1)		(0.35	)		(0.40	)		(0.33	)		(0.41	)


(1)	Per common share amounts for the quarters and full years have been calculated separately. Accordingly, quarterly amounts do not add to the annual amounts because of differences on the weighted-average common shares outstanding during each period principally due to the effect of the Company issuing shares of its common stock during the year.

Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended		3 Months Ended	4 Months Ended	12 Months Ended
	Feb. 21, 2018	Feb. 15, 2018	Jul. 18, 2017	Jul. 05, 2016	Jul. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Jul. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Corporate Information, Status of Operations and Management Plans
Loss on impairment of intangible assets									$ 463,700
Changes in fair value of contingent consideration payable									234,322	$ (6,760)	$ (4,377)
Contingent consideration payable						$ 269,722			25,400	269,722
Income tax benefit									(165,119)	(3,739)
Number of common stock shares issued from underwriting agreement					21,122,449
Price per share of common stock issued (in dollars per share)					$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions					$ 258,800				243,037		243,042
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000						$ 243,037	$ 97,068	$ 243,042
Common stock, par value (in dollars per share)						$ 0.01			$ 0.01	$ 0.01
Net proceeds from convertible notes to pay capped call transactions										$ 13,450
Net proceeds from stock issued at ATM transactions										97,068
Accumulated deficit						$ (779,608)			$ (1,063,610)	$ (779,608)
SD-101
Corporate Information, Status of Operations and Management Plans
Loss on impairment related to fixed assets									1,700
Changes in fair value of contingent consideration payable							$ 254,700
Contingent consideration payable							0
Selling, general and administrative costs due to wind-down							400
Research and development expenses due to wind-down							8,100
Income tax benefit							$ 164,700		$ 164,700
Cowen and Company, LLC \| Sales Agreement
Corporate Information, Status of Operations and Management Plans
Number of shares issued from ATM transactions (in shares)								15,000,000
Net proceeds from stock issued at ATM transactions								$ 97,100
Commission expenses incurred on issue of common stock								2,700
Other expenses paid								$ 200
Common Stock
Corporate Information, Status of Operations and Management Plans
Number of common stock shares issued from underwriting agreement					21,122,449				21,122,449		19,528,302
Price per share of common stock issued (in dollars per share)					$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions					$ 258,800				$ 212		$ 195
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000
Number of shares issued from ATM transactions (in shares)										14,989,027
Net proceeds from stock issued at ATM transactions										$ 150
Common Stock \| Subsequent event
Corporate Information, Status of Operations and Management Plans
Number of common stock shares issued from underwriting agreement		19,354,839
Price per share of common stock issued (in dollars per share)		$ 15.50
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions		$ 300,000
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions	$ 282,000
Convertible Notes \| 2016 Convertible Notes
Corporate Information, Status of Operations and Management Plans
Aggregate principal amount						$ 250,000				$ 250,000
Fixed interest rate (as a percent)						3.00%				3.00%
Proceeds from convertible notes, Net of issuance costs						$ 243,000
Net proceeds from convertible notes to pay capped call transactions						$ 13,500
Maximum \| Cowen and Company, LLC \| Sales Agreement
Corporate Information, Status of Operations and Management Plans
Fixed commission rate as a percentage of gross proceeds per Share sold								3.00%
IPR&D \| SD-101
Corporate Information, Status of Operations and Management Plans
Loss on impairment of intangible assets									$ 463,700
MiaMed Inc
Corporate Information, Status of Operations and Management Plans
Asset acquisition, potential aggregate deal value				$ 89,500
Asset acquisition, total consideration, stock and cash				6,500
MiaMed Inc \| Clinical, Regulatory and Commercial milestones \| Maximum
Corporate Information, Status of Operations and Management Plans
Contingent consideration payable upon achievement of milestones				$ 83,000

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Property and Equipment
Estimated useful lives	3 years
Maximum
Property and Equipment
Estimated useful lives	5 years

Summary of Significant Accounting Policies - Equity Incentive Plan and Stock-Based Compensation (Details)	Dec. 31, 2017 item
Equity-based Compensation
Number of equity-based employee compensation plans	3

Summary of Significant Accounting Policies - Segment Information and Recent Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017 segment
Summary of Significant Accounting Policies
Number of business segments	1

Summary of Significant Accounting Policies - Recent Accounting Policies (Details) - Accounting Standards Update 2016-09 - Adjustment $ in Millions	Jan. 01, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Amount of net operating loss carry forwards	$ 4.0
Net operating loss carryforward, valuation allowance	$ 4.0

Acquisitions (Details) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended	12 Months Ended
Acquisitions (Details) - USD ($) $ in Thousands	Jul. 05, 2016	Sep. 30, 2017	Apr. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Charges to research expense for stock issued in asset acquisition						$ 4,607
Contingent consideration payable					$ 25,400	269,722
Contingent consideration payable, current portion					8,400	56,101
Contingent consideration payable, non-current portion					17,000	213,621
Changes in fair value of contingent consideration payable					(234,322)	$ 6,760	$ 4,377
MiaMed Inc
Acquisitions
Asset acquisition, total consideration, stock and cash	$ 6,500
Asset acquisition, cash consideration paid	1,800
Asset acquisition, potential aggregate deal value	89,500
Charges to research expense for stock issued in asset acquisition	$ 6,500
MiaMed Inc \| Amicus \| Common Stock
Acquisitions
Consideration paid in common stock	825,603
Scioderm
Acquisitions
Enrollment rate (as a percent)				100.00%
Milestone payment			$ 10,000
Scioderm \| Amicus \| Common Stock
Acquisitions
Consideration paid in common stock		5,900,000
Callidus
Acquisitions
Contingent consideration payable					25,400
Contingent consideration payable, current portion					8,400
Contingent consideration payable, non-current portion					17,000
Callidus \| Changes in fair value of contingent consideration payable
Acquisitions
Changes in fair value of contingent consideration payable					$ (15,700)
Clinical, Regulatory and Commercial milestones \| MiaMed Inc \| Maximum
Acquisitions
Contingent consideration payable upon achievement of milestones	$ 83,000

Goodwill and Intangible Assets - IPR&D (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Changes in IPR&D
Balance at beginning of the period	$ 486.7
Impairment in IPR&D related to Scioderm	(463.7)
Balance at end of the period	23.0
Business Acquisitions
Changes in IPR&D
Balance at end of the period	$ 486.7

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Changes in goodwill
Balance at beginning of the period	$ 197,797
Balance at end of the period	197,797
Goodwill
Changes in goodwill
Balance at beginning of the period	197,800
Balance at end of the period	197,800
Business Acquisitions \| Goodwill
Changes in goodwill
Balance at end of the period	$ 197,800

Cash, Money Market Funds and Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash, Money Market Funds, and Marketable Securities
Cash and cash equivalents, Amortized Cost	$ 49,060	$ 187,026	$ 69,485	$ 24,074
Cash and cash equivalents, Fair Value	49,060	187,026
Marketable securities, Amortized Cost	309,938	143,222
Gross Unrealized Gain	1	134
Gross Unrealized Loss	(437)	(31)
Marketable securities, Fair Value	309,502	143,325
Cash and marketable securities, Amortized Cost	358,998	330,248
Cash and marketable securities, Fair Value	358,562	330,351
Available-for-sale investments
Realized gain (loss) on securities available-for-sale	0	0
Fair value of available for sale securities in unrealized loss positions	295,100	58,700
Other current liabilities \| Foreign exchange forward contract \| Not designated
Cash, Money Market Funds, and Marketable Securities
Derivative liabilities	0	300
Other expense \| Foreign exchange forward contract \| Not designated
Cash, Money Market Funds, and Marketable Securities
Loss on derivative instruments	200	300
Corporate debt securities, current portion
Cash, Money Market Funds, and Marketable Securities
Marketable securities, Amortized Cost	199,314	74,564
Gross Unrealized Gain	1	2
Gross Unrealized Loss	(303)	(31)
Marketable securities, Fair Value	199,012	74,535
Commercial paper
Cash, Money Market Funds, and Marketable Securities
Marketable securities, Amortized Cost	79,878	68,258
Gross Unrealized Gain		132
Gross Unrealized Loss	(75)
Marketable securities, Fair Value	79,803	68,390
Asset-backed securities
Cash, Money Market Funds, and Marketable Securities
Marketable securities, Amortized Cost	30,346
Gross Unrealized Loss	(59)
Marketable securities, Fair Value	30,287
Money market funds
Cash, Money Market Funds, and Marketable Securities
Marketable securities, Amortized Cost	350	350
Marketable securities, Fair Value	350	350
Certificate of deposit
Cash, Money Market Funds, and Marketable Securities
Marketable securities, Amortized Cost	50	50
Marketable securities, Fair Value	$ 50	$ 50

Inventories (Details) - USD ($) $ in Thousands	24 Months Ended
Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventories
Work-in-process	$ 3,843	$ 3,308
Finished goods	780	108
Total inventories	4,623	$ 3,416
Inventory write-downs	$ 0

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Property and equipment, gross	$ 21,577	$ 22,311
Less accumulated depreciation	(12,515)	(12,495)
Property and equipment, net	9,062	9,816
Depreciation	3,593	3,242	$ 1,833
Computer equipment
Property and Equipment
Property and equipment, gross	3,746	3,511
Computer software
Property and Equipment
Property and equipment, gross	1,236	1,347
Research equipment
Property and Equipment
Property and equipment, gross	6,379	7,465
Furniture and fixtures
Property and Equipment
Property and equipment, gross	2,992	3,018
Leasehold improvements
Property and Equipment
Property and equipment, gross	7,193	$ 6,970
Construction in progress
Property and Equipment
Property and equipment, gross	$ 31

Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts payable and accrued expenses
Accounts payable	$ 7,867	$ 12,905
Accrued professional fees	5,845	5,079
Accrued contract manufacturing & contract research costs	4,632	8,042
Accrued compensation and benefits	19,620	9,686
Accrued facility costs	1,665	1,740
Accrued program fees	5,707
Foreign currency forward contract		265
Capital lease, short term portion	307	283
Royalties payable	2,529	510
Accrued interest	313	208
Accrued other	5,405	2,290
Accounts payable and accrued expenses	$ 53,890	$ 41,008

Stockholders' Equity - Common Stock and Warrants (Details)						1 Months Ended				4 Months Ended	12 Months Ended
	Feb. 21, 2018 USD ($)	Feb. 15, 2018 USD ($) $ / shares shares	Jul. 18, 2017 USD ($)	Dec. 21, 2016 USD ($) $ / shares	Jul. 05, 2016 USD ($) shares	Sep. 30, 2017 USD ($) shares	Jul. 31, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Feb. 29, 2016 USD ($) shares	Jul. 31, 2016 USD ($) shares	Dec. 31, 2017 USD ($) item $ / shares shares	Dec. 31, 2016 USD ($) item $ / shares shares	Dec. 31, 2015 USD ($) shares	Oct. 31, 2015 USD ($) shares
Convertible Debt
Authorized number of shares of common stock \| shares											250,000,000	250,000,000
Voting right for each share held, number \| item											1	1
Common stock, par value (in dollars per share) \| $ / shares											$ 0.01	$ 0.01
Number of common stock shares issued from underwriting agreement \| shares							21,122,449
Price per share of common stock issued (in dollars per share) \| $ / shares							$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions							$ 258,800,000				$ 243,037,000		$ 243,042,000
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000,000								243,037,000	$ 97,068,000	$ 243,042,000
Net proceeds from stock issued at ATM transactions												97,068,000
Warrant liability											$ 16,076,000	$ 16,076,000
Common Stock
Convertible Debt
Number of common stock shares issued from underwriting agreement \| shares							21,122,449				21,122,449		19,528,302
Price per share of common stock issued (in dollars per share) \| $ / shares							$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions							$ 258,800,000				$ 212,000		$ 195,000
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000,000
Number of shares issued from ATM transactions (in shares) \| shares												14,989,027
Net proceeds from stock issued at ATM transactions												$ 150,000
Cowen and Company, LLC \| Sales Agreement
Convertible Debt
Number of shares issued from ATM transactions (in shares) \| shares										15,000,000
Net proceeds from stock issued at ATM transactions										$ 97,100,000
Commission expenses incurred on issue of common stock										2,700,000
Other Expenses										$ 200,000
Cowen and Company, LLC \| Sales Agreement \| Maximum
Convertible Debt
Fixed commission rate as a percentage of gross proceeds per Share sold										3.00%
Scioderm
Convertible Debt
Initial amount to Effective Time Holders						$ 223,900,000
Initial amount cash payment excluding Series B Preferred						141,100,000
Initial amount paid in shares of Common Stock						$ 82,800,000
Scioderm \| Amicus \| Common Stock
Convertible Debt
Consideration paid in common stock \| shares						5,900,000
MiaMed Inc
Convertible Debt
Asset acquisition, total consideration, stock and cash					$ 6,500,000
Asset acquisition, cash consideration paid					1,800,000
Asset acquisition, potential aggregate deal value					89,500,000
MiaMed Inc \| Maximum \| Clinical, Regulatory and Commercial milestones
Convertible Debt
Contingent consideration payable upon achievement of milestones					$ 83,000,000
MiaMed Inc \| Amicus \| Common Stock
Convertible Debt
Consideration paid in common stock \| shares					825,603
October 2015 Notes and Warrants Purchase Agreement \| Redmile Group
Convertible Debt
Fixed interest rate (as a percent)														4.10%
Warrant liability														$ 8,800,000
October 2015 Notes and Warrants Purchase Agreement \| Redmile Group \| Private Placement Purchase Agreement
Convertible Debt
Aggregate principal amount														$ 50,000,000
October 2015 Notes and Warrants Purchase Agreement \| Redmile Group \| Private Placement Purchase Agreement \| Warrants
Convertible Debt
Shares issuable for warrants (in shares) \| shares														1,300,000
February 2016 Notes and Warrants Purchase Agreement \| Beneficial Owner \| Redmile Group \| Maximum
Convertible Debt
Aggregate principal amount									$ 75,000,000
February 2016 Notes and Warrants Purchase Agreement \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement
Convertible Debt
Aggregate principal amount									$ 50,000,000
Fixed interest rate (as a percent)									3.875%
February 2016 Notes and Warrants Purchase Agreement \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement \| Warrants
Convertible Debt
Increment used for debt conversion									$ 1,000
Shares issuable for warrants (in shares) \| shares									1,800,000
February 2016 Notes and Warrants Purchase Agreement \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement \| Maximum
Convertible Debt
Shares issuable for warrants (in shares) \| shares									1,850,000
2016 Convertible Notes \| Convertible Notes
Convertible Debt
Aggregate principal amount												$ 250,000,000
Fixed interest rate (as a percent)												3.00%
Debt conversion ratio (in shares)				0.1633987
Increment used for debt conversion				$ 1,000
Conversion price (in dollars per share) \| $ / shares				$ 6.12
Additional Note and Warrant Agreement June 2016 \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement
Convertible Debt
Aggregate principal amount								$ 30,000,000
Fixed interest rate (as a percent)								3.875%
Common stock, par value (in dollars per share) \| $ / shares								$ 0.01
Additional Note and Warrant Agreement June 2016 \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement \| Warrants
Convertible Debt
Increment used for debt conversion								$ 1,000
Shares issuable for warrants (in shares) \| shares								1,300,000
Additional Note and Warrant Agreement June 2016 \| Beneficial Owner \| Redmile Group \| Private Placement Purchase Agreement \| Maximum \| Warrants
Convertible Debt
Shares issuable for warrants (in shares) \| shares								1,260,000
Subsequent event \| Common Stock
Convertible Debt
Number of common stock shares issued from underwriting agreement \| shares		19,354,839
Price per share of common stock issued (in dollars per share) \| $ / shares		$ 15.50
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions		$ 300,000,000
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions	$ 282,000,000

Stockholders' Equity - Nonqualified Cash Plan and Equity Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Aggregate Intrinsic Value
Proceeds from exercise of stock options	$ 16,301	$ 3,036	$ 11,186
Nonqualified Cash Plan (the "Deferral Plan")
Stockholders' Equity
Deferred compensation investment	2,248	1,469
Deferred compensation liability	2,258	1,479
Investment income	66	34
Unrealized gain	$ 92	$ 32
Common stock options
Fair value weighted-average assumptions:
Maximum term of option	10 years
Expected stock price volatility (as a percent)	82.80%	81.30%	75.90%
Risk free interest rate (as a percent)	2.00%	1.50%	1.70%
Expected life of options	6 years 2 months 5 days	6 years 3 months	6 years 3 months
Expected annual dividend per share (in dollars per share)	$ 0.00	$ 0.00	$ 0.00
Granted (in dollars per share)	$ 5.09	$ 5.28	$ 7.51
Number of Shares
Balance at the beginning of the period (in shares)	15,497,500	11,729,200	10,020,700
Options granted (in shares)	3,695,300	5,114,100	3,917,200
Options exercised (in shares)	(2,878,700)	(723,100)	(2,070,300)
Options forfeited (in shares)	(1,133,000)	(622,700)	(138,400)
Balance at the end of the period (in shares)	15,181,100	15,497,500	11,729,200
Vested and unvested expected to vest as of the end of the period (in shares)	14,398,500
Exercisable at the end of the period (in shares)	7,985,600
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 7.37	$ 7.11	$ 5.02
Options granted (in dollars per share)	7.17	7.67	11.61
Options exercised (in dollars per share)	5.67	4.20	5.43
Options forfeited (in dollars per share)	9.55	8.62	7.76
Balance at the end of the period (in dollars per share)	7.48	$ 7.37	$ 7.11
Vested and unvested expected to vest as of the end of the period (in dollars per share)	7.45
Exercisable at the end of the period (in dollars per share)	$ 7.05
Weighted Average Remaining Contractual Life
Balance at the end of the period	7 years 2 months 12 days
Vested and unvested expected to vest at the end of the period	7 years 1 month 6 days
Exercisable at the end of the period	6 years
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding (in dollars)	$ 105,800
Aggregate intrinsic value of options vested and unvested expected to vest (in dollars)	100,900
Aggregate intrinsic value of options exercisable (in dollars)	59,100
Aggregate intrinsic value of options exercised (in dollars)	20,800	$ 2,600	$ 14,700
Proceeds from exercise of stock options	16,300	$ 3,000	$ 11,200
Total unrecognized compensation cost related to non-vested stock options granted (in dollars)	$ 31,900
Period of recognition unrecognized compensation costs (in years)	2 years 6 months
Common stock options \| 2007 Plan and 2007 Director Plan
Fair value weighted-average assumptions:
Percentage of options vest on the first year anniversary		25.00%
Vesting percentage		2.08%
Percentage of shares vested that may be exercised in whole or part		100.00%
Restricted stock units (RSUs) \| Amended and Restated 2007 Equity Incentive Plan
Aggregate Intrinsic Value
Estimated fair value (in dollars per share)	$ 5.69	$ 6.21
Period of recognition unrecognized compensation costs (in years)	2 years 5 months 19 days
Restricted Stock Units, Number of Shares
Non-vested units as of the beginning of the period (in shares)	744,400	478,500
Granted (in shares)	2,348,700	582,700
Vested (in shares)	(318,200)	(281,900)
Forfeited (in shares)	(199,800)	(34,900)
Non-vested units as of the end of the period (in shares)	2,575,100	744,400	478,500
Weighted Average Grant Date Fair Value
Non-vested units as of the beginning of the period (in dollars per share)	$ 7.86	$ 10.38
Granted (in dollars per share)	5.69	6.21
Vested (in dollars per share)	9.23	8.73
Forfeited (in dollars per share)	6.24	7.71
Non-vested units as of the end of the period (in dollars per share)	$ 5.85	$ 7.86	$ 10.38
Weighted Average Remaining Years
Non-vested units as of the end of the period	2 years 5 months 19 days
Aggregate Intrinsic Value
Non-vested units as of the end of the period (in dollars)	$ 37,100
Unrecognized compensation cost related to unvested RSU's (in dollars)	$ 11,400
Clinical milestone \| Restricted stock units (RSUs) \| Amended and Restated 2007 Equity Incentive Plan
Aggregate Intrinsic Value
Vesting period	3 years
Restricted Stock Units, Number of Shares
Granted (in shares)	401,413
Executive Officers \| Market Performance-based Restricted Stock Units (MPRSUs) \| Amended and Restated 2007 Equity Incentive Plan
Aggregate Intrinsic Value
Vesting period	3 years
Estimated fair value (in dollars per share)	$ 8.08
Restricted Stock Units, Number of Shares
Granted (in shares)	401,413
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 8.08
Executive Officers \| Market Performance-based Restricted Stock Units (MPRSUs) \| Amended and Restated 2007 Equity Incentive Plan \| Cliff Vesting
Aggregate Intrinsic Value
Vesting period	3 years
Maximum \| Common stock options \| 2007 Plan and 2007 Director Plan
Fair value weighted-average assumptions:
Number of shares reserved for issuance	7,855,550
Maximum \| Executive Officers \| Market Performance-based Restricted Stock Units (MPRSUs) \| Amended and Restated 2007 Equity Incentive Plan
Fair value weighted-average assumptions:
Vesting percentage	200.00%
Number of Shares
Exercisable at the end of the period (in shares)	802,826

Stockholders' Equity - Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity compensation expense
Total equity compensation expense	$ 23,101	$ 17,504	$ 9,972
Research and development expense
Equity compensation expense
Total equity compensation expense	10,328	8,071	4,600
Selling, general and administrative expense
Equity compensation expense
Total equity compensation expense	$ 12,773	$ 9,433	$ 5,372

Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 05, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016	Oct. 31, 2015
Financial assets and liabilities subject to fair value measurements
Transfer of assets from Level 1 to Level 2		$ 0
Transfer of assets from Level 2 to Level 1		0
Assets:
Fair value of assets		311,700	$ 144,754
Liabilities:
Contingent consideration payable		25,400	269,722
Derivative liability			265
Deferred compensation plan liability		2,258	1,479
Fair value of liabilities		27,658	271,466
Contingent consideration payable
Balance, beginning of the period		269,722	274,077
Payment of contingent consideration in cash		(10,000)	(5,000)
Payment of contingent consideration in stock			(6,115)
Unrealized change in fair value change during the period, included in Statement of Operations		(234,322)	6,760	$ 4,377
Balance, end of the period		25,400	269,722	$ 274,077
Callidus
Liabilities:
Contingent consideration payable		25,400
MiaMed Inc
Contingent consideration payable
Asset acquisition, potential aggregate deal value	$ 89,500
Clinical and Regulatory Approval milestones \| Callidus
Liabilities:
Contingent consideration payable		25,000
Maximum \| Clinical, Regulatory and Commercial milestones \| MiaMed Inc
Liabilities:
Contingent consideration payable upon achievement of milestones	83,000
Contingent consideration payable
Contingent consideration payable upon achievement of milestones	$ 83,000
Commercial paper
Assets:
Fair value of assets		79,803	68,390
Asset-backed securities
Assets:
Fair value of assets		30,287
Corporate debt securities
Assets:
Fair value of assets		199,012	74,535
Money market funds
Assets:
Fair value of assets		2,598	1,829
Level 2
Assets:
Fair value of assets		311,700	144,754
Liabilities:
Derivative liability			265
Deferred compensation plan liability		2,258	1,479
Fair value of liabilities		2,258	1,744
Level 2 \| Commercial paper
Assets:
Fair value of assets		79,803	68,390
Level 2 \| Asset-backed securities
Assets:
Fair value of assets		30,287
Level 2 \| Corporate debt securities
Assets:
Fair value of assets		199,012	74,535
Level 2 \| Money market funds
Assets:
Fair value of assets		2,598	1,829
Level 3
Liabilities:
Contingent consideration payable		25,400	269,722
Fair value of liabilities		$ 25,400	$ 269,722
Level 3 \| Clinical and Regulatory Approval milestones \| Probability weighted discounted cash flow \| Callidus
Liabilities:
Discount rate (as a percent)		11.50%
Level 3 \| Minimum \| Clinical and Regulatory Approval milestones \| Probability weighted discounted cash flow \| Callidus
Liabilities:
Probability of achievement of milestones (as a percent)		71.00%
Level 3 \| Maximum \| Clinical and Regulatory Approval milestones \| Probability weighted discounted cash flow \| Callidus
Liabilities:
Probability of achievement of milestones (as a percent)		100.00%
Redmile Group \| October 2015 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement
Financial assets and liabilities subject to fair value measurements
Debt Instrument, Face Amount						$ 50,000
Redmile Group \| Additional Note and Warrant Agreement June 2016 \| Beneficial Owner \| Private Placement Purchase Agreement
Financial assets and liabilities subject to fair value measurements
Debt Instrument, Face Amount					$ 30,000

Debt Instruments and Related Party Transactions - Notes and Warrants Purchase Agreements (Details)	1 Months Ended			12 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares	Feb. 29, 2016 USD ($) item shares	Oct. 31, 2015 USD ($) installment shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) $ / shares
Debt Instruments
Warrants				$ 16,076,000		$ 16,076,000
Common stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01
Loss on extinguishment of debt				$ 13,302,000	$ 952,000
Redmile Group \| October 2015 Notes and Warrants Purchase Agreement
Debt Instruments
Number of installments for repayment of debt \| installment			2
Fixed interest rate (as a percent)			4.10%
Warrants			$ 8,800,000
Redmile Group \| October 2015 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement
Debt Instruments
Ownership position in the company (as a percent)			6.70%
Proceeds from note and warrant purchase agreement			$ 50,000,000
Redmile Group \| October 2015 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Warrants
Debt Instruments
Warrant Term			5 years
Shares issuable for warrants (in shares) \| shares			1,300,000
Redmile Group \| February 2016 Notes and Warrants Purchase Agreement \| Beneficial Owner \| Maximum
Debt Instruments
Proceeds from note and warrant purchase agreement		$ 75,000,000
Redmile Group \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner
Debt Instruments
Proceeds from note and warrant purchase agreement		$ 50,000,000
Number of installments for repayment of debt \| item		2
Fixed interest rate (as a percent)		3.875%
Redmile Group \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner \| Maximum
Debt Instruments
Shares issuable for warrants (in shares) \| shares		1,850,000
Redmile Group \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner \| Warrants
Debt Instruments
Warrant Term		5 years
Shares issuable for warrants (in shares) \| shares		1,800,000
Increment used for debt conversion		$ 1,000
Incremental fair value of warrant liability		$ 3,500,000
Redmile Group \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner \| Warrants \| Maximum
Debt Instruments
Shares of common stock issued per increment of note principal \| shares		37
Redmile Group \| Additional Note and Warrant Agreement June 2016 \| Private Placement Purchase Agreement \| Beneficial Owner
Debt Instruments
Proceeds from note and warrant purchase agreement	$ 30,000,000
Fixed interest rate (as a percent)	3.875%
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01
Redmile Group \| Additional Note and Warrant Agreement June 2016 \| Private Placement Purchase Agreement \| Beneficial Owner \| Warrants
Debt Instruments
Warrant Term	5 years
Shares issuable for warrants (in shares) \| shares	1,300,000
Increment used for debt conversion	$ 1,000
Redmile Group \| Additional Note and Warrant Agreement June 2016 \| Private Placement Purchase Agreement \| Beneficial Owner \| Warrants \| Maximum
Debt Instruments
Shares issuable for warrants (in shares) \| shares	1,260,000
Shares of common stock issued per increment of note principal \| shares	42
Redmile Group \| December 2016 Note Purchase Agreement
Debt Instruments
Loss on extinguishment of debt				$ 13,300,000
Redmile Group \| October 2017 payment \| October 2015 Notes and Warrants Purchase Agreement
Debt Instruments
Installment payment			$ 15,000,000
Redmile Group \| October 2017 payment \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner
Debt Instruments
Installment payment		$ 15,000,000
Redmile Group \| October 2020 payment \| October 2015 Notes and Warrants Purchase Agreement
Debt Instruments
Installment payment			$ 35,000,000
Redmile Group \| October 2021 payment \| February 2016 Notes and Warrants Purchase Agreement \| Private Placement Purchase Agreement \| Beneficial Owner
Debt Instruments
Installment payment		$ 35,000,000

Debt Instruments and Related Party Transactions - Convertible Debt (Details)			1 Months Ended	12 Months Ended
	Dec. 21, 2016 USD ($) D $ / shares shares	Dec. 15, 2016 $ / item	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Convertible Debt
Net proceeds from convertible notes to pay capped call transactions					$ 13,450,000
Equity component of the Convertible Notes					88,346,000
Deferred tax liability in relation to the Convertible Notes			$ 29,845,000	$ 18,991,000	29,845,000
Convertible notes issuance costs			2,709,000		2,709,000
Convertible Notes \| 2016 Convertible Notes
Convertible Debt
Aggregate principal amount			250,000,000		250,000,000
Net proceeds after deducting fees and estimated expenses			243,000,000
Net proceeds from convertible notes to pay capped call transactions			13,500,000
Shares of common stock issued per increment of note principal \| shares	40,849,675
Debt conversion ratio (in shares)	0.1633987
Increment used for debt conversion	$ 1,000
Conversion price (in dollars per share) \| $ / shares	$ 6.12
Maximum calendar days allowed to holders of common stock rights options or warrants to purchase of common stock	60 days
Trading days for price per share based on last reported sale price	10 days
Minimum percentage of per share value of last reported sale price of common stock	10.00%
Debt instrument term	7 years
Equity component of the Convertible Notes	$ 88,300,000
Convertible notes issuance costs	7,500,000
Convertible notes issuance cost paid	$ 6,900,000
Liability components of convertible notes
Principal			250,000,000	250,000,000	250,000,000
Less: debt discount			(90,807,000)	(81,566,000)	(90,807,000)
Less: deferred financing			(4,729,000)	(4,267,000)	(4,729,000)
Net carrying value of the debt			$ 154,464,000	164,167,000	154,464,000
Fair value of the debt				633,400,000
Interest expense
Contractual interest expense				7,528,000	208,000
Amortization of deferred financing				470,000	26,000
Amortization of debt discount				9,241,000	248,000
Total interest expense				$ 17,239,000	$ 482,000
Effective interest rate of the liability component			10.85%	10.85%	10.85%
Initial cap price \| $ / item		7.20
Capped call premium on closing price		50.00%
Convertible Notes \| 2016 Convertible Notes \| Convertible Notes, condition 1
Convertible Debt
Threshold consecutive trading days \| D	30
Threshold percentage	130.00%
Convertible Notes \| 2016 Convertible Notes \| Convertible Notes, condition 1 \| Minimum
Convertible Debt
Threshold trading days	20 days
Convertible Notes \| 2016 Convertible Notes \| Convertible Notes, condition 2
Convertible Debt
Threshold trading days	5 days
Threshold consecutive trading days \| D	5
Maximum threshold percentage	98.00%
Over-allotment Option \| Private Placement Purchase Agreement \| Convertible Notes \| 2016 Convertible Notes
Convertible Debt
Aggregate principal amount			$ 25,000,000		$ 25,000,000

Leases (Details) $ in Thousands	12 Months Ended
Leases (Details) $ in Thousands	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Minimum lease payments
2018	$ 2,762
2019	2,575
2020	2,472
2021	2,240
2022 and beyond	8,467
Total	18,516
Rent expense, including fees for utilities and common area maintenances	3,900	$ 3,500	$ 2,600
Equipment
Capital Leases
Capital lease obligation		$ 900
2018	356
2019	134
Total principal obligation	$ 490
Equipment \| Minimum
Capital Leases
Fixed interest rate (as a percent)		0.20%
Term of capital lease (in months)		36 months
Equipment \| Maximum
Capital Leases
Fixed interest rate (as a percent)		5.70%
Term of capital lease (in months)		48 months
Cranbury, New Jersey \| Office and laboratory space
Operating Leases
Area of space leased (in square feet) \| ft²	90,000
Durham, North Carolina \| Office space
Operating Leases
Area of space leased (in square feet) \| ft²	5,603
Buckinghamshire, United Kingdom \| Office space
Operating Leases
Area of space leased (in square feet) \| ft²	9,821
Munich, Germany \| Office space
Operating Leases
Area of space leased (in square feet) \| ft²	4,751

Income Taxes - Statutory Rate (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) before income taxes:
United States			$ (440,696)	$ (174,913)	$ (123,697)
Foreign			(8,425)	(28,868)	(8,421)
Loss before income tax benefit			(449,121)	(203,781)	$ (132,118)
Current:
State			9	7
Foreign			2,276
Deferred
Federal			(150,015)	(1,101)
State			(17,389)	(2,645)
Total			$ (165,119)	$ (3,739)
Reconciliation of the statutory tax rates and the effective tax rates
Statutory rate (as a percent)			(34.00%)	(34.00%)	(34.00%)
State taxes, net of federal benefit (as a percent)			(5.00%)	(5.00%)	(5.00%)
Permanent adjustments (as a percent)			(1.00%)	3.00%	2.00%
Contingent consideration (as a percent)			(18.00%)
R&D credit (as a percent)			(2.00%)	(3.00%)	(3.00%)
Foreign income tax rate differential (as a percent)			5.00%	2.00%	1.00%
Impact of 2017 Act (as a percent)			27.00%
Other (as a percent)			5.00%	(1.00%)	2.00%
Valuation allowance (as a percent)			(14.00%)	36.00%	37.00%
Net (as a percent)			(37.00%)	(2.00%)	(0.00%)
Income tax benefit on reduction of income tax rate			$ (2,700)
Income tax benefit			(165,119)	$ (3,739)
Forecast
Reconciliation of the statutory tax rates and the effective tax rates
Statutory rate (as a percent)		(21.00%)
SD-101
Deferred
Total	$ 164,700		164,700
Reconciliation of the statutory tax rates and the effective tax rates
Income tax benefit	$ 164,700		$ 164,700

Income Taxes - Deferred and Valuation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Foreign and state income tax expenses	$ 2,300
Accrual for interest and penalties	0
Accrual for uncertain tax positions	0
Deferred tax assets
Intellectual property	44,573	$ 95,956
Amortization/depreciation	3,082	1,781
Research tax credit	43,382	32,851
Net operating loss carry forwards	221,912	223,758
Deferred revenue	6,158	14,281
Non-cash stock issue	10,751	11,649
Others	7,328	3,358
Gross deferred tax assets	337,186	383,634
Business acquisition	(6,465)	(173,771)
Royalty payable	(44,573)	(96,829)
Convertible notes	(18,991)	(29,845)
Advanced R&D payments	(3,069)
Total net deferred tax asset	264,088	83,189
Less valuation allowance	(270,553)	(256,960)
Net deferred tax liability	(6,465)	$ (173,771)
Increase in the valuation allowance	$ 13,600

Income Taxes - Loss Carryforwards (Details) $ in Millions	12 Months Ended
Income Taxes - Loss Carryforwards (Details) $ in Millions	Dec. 31, 2017 USD ($)
Net operating loss carry forwards
Period for measuring the change in ownership	3 years
Maximum change in ownership percentage allowed before statutory limitations imposed on the availability of net operating losses	50.00%
Research and experimentation tax credit carryforward
Net operating loss carry forwards
Tax credit carryforward amount	$ 35.2
Orphan drug tax credit carryforwards
Net operating loss carry forwards
Tax credit carryforward amount	8.2
Federal
Net operating loss carry forwards
Amount of net operating loss carry forwards	777.6
Write-down of NOLs and R&D credits subject to section 382 limitation	0.0
State
Net operating loss carry forwards
Amount of net operating loss carry forwards	781.8
Foreign
Net operating loss carry forwards
Amount of net operating loss carry forwards	$ 47.1

Licenses (Details) - License agreement - MSSM	12 Months Ended
Licenses (Details) - License agreement - MSSM	Dec. 31, 2017 USD ($)
Licenses
Upfront and annual license fees paid	$ 0
Potential milestone payments	0
Royalty expense	$ 1,100,000

Collaborative Agreements (Details) $ in Thousands	1 Months Ended	12 Months Ended
Collaborative Agreements (Details) $ in Thousands	Nov. 30, 2013 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaborative Agreements
Deferred reimbursements		$ 14,156	$ 21,906
Accounts payable, accrued expenses, and other current liabilities		53,890	$ 41,008
GSK \| Revised Agreement
Collaborative Agreements
Upfront payment received	$ 0
Potential milestone payments upon achievement of post-approval and sales-based milestones	$ 40,000
Number of major markets outside the U.S. from whom parties to contractual arrangement is eligible to receive post-approval and sales-based milestones \| item	8
Milestone revenue recognized		3,900
Deferred reimbursements		21,900
Accounts payable, accrued expenses, and other current liabilities		$ 1,300

Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Earnings per Share (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss attributable to common stockholders	$ (69,208)	$ (111,666)	$ (48,136)	$ (54,992)	$ (58,647)	$ (46,654)	$ (51,050)	$ (43,691)	$ (284,002)	$ (200,042)	$ (132,118)
Denominator:
Weighted average common shares outstanding - basic and diluted									153,355,144	134,401,588	109,923,815
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									61,766,000	60,232,000	13,558,000
Common stock options
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									15,181,000	15,528,000	11,729,000
Convertible debt
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									40,850,000	40,850,000
Warrants
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									3,110,000	3,110,000	1,350,000
Restricted stock units (RSUs)
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									2,575,000	744,000	479,000
Vested restricted stock units, unissued
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)									50,000

Commitments and Contingencies (Details) $ in Millions	Nov. 15, 2017 USD ($)	Dec. 31, 2017 lawsuit
Commitments and Contingencies
Number of purported securities class action lawsuits		3
Number of purported securities class action lawsuits naming additional company officers as defendants		1
Settlement Fund for class members \| $	$ 3.8

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Feb. 21, 2018	Feb. 15, 2018	Jul. 18, 2017	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Events
Number of common stock shares issued from underwriting agreement				21,122,449
Price per share of common stock issued (in dollars per share)				$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions				$ 258,800	$ 243,037		$ 243,042
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000		$ 243,037	$ 97,068	$ 243,042
Common Stock
Subsequent Events
Number of common stock shares issued from underwriting agreement				21,122,449	21,122,449		19,528,302
Price per share of common stock issued (in dollars per share)				$ 12.25
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions				$ 258,800	$ 212		$ 195
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions			$ 243,000
Subsequent event \| Common Stock
Subsequent Events
Number of common stock shares issued from underwriting agreement		19,354,839
Price per share of common stock issued (in dollars per share)		$ 15.50
Gross proceeds from issue of common stock before deducting underwriting discounts and commissions		$ 300,000
Net proceeds from the issuance of common stock after deducting underwriting discounts and commissions	$ 282,000

Selected Quarterly Financial Data (Unaudited - in thousands except per share data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data
Net loss	$ (69,208)	$ (111,666)	$ (48,136)	$ (54,992)	$ (58,647)	$ (46,654)	$ (51,050)	$ (43,691)	$ (284,002)	$ (200,042)	$ (132,118)
Basic and diluted net loss per common share (in dollars per share)	$ (0.42)	$ (0.69)	$ (0.34)	$ (0.39)	$ (0.41)	$ (0.33)	$ (0.40)	$ (0.35)	$ (1.85)	$ (1.49)	$ (1.20)