Horizon Therapeutics Public (HZNP) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 22, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	HZNP
Entity Registrant Name	HORIZON PHARMA PLC
Entity Central Index Key	1,492,426
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		164,570,004
Entity Public Float			$ 1.9

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 751,368	$ 509,055
Restricted cash	6,529	7,095
Accounts receivable, net	367,351	305,725
Inventories, net	61,655	174,788
Prepaid expenses and other current assets	43,402	49,619
Total current assets	1,230,305	1,046,282
Property and equipment, net	20,405	23,484
Intangible assets, net	2,449,390	2,773,435
Goodwill	426,441	445,579
Deferred tax assets, net	3,470	911
Other assets	36,081	2,368
Total assets	4,166,092	4,292,059
CURRENT LIABILITIES:
Long-term debt—current portion	10,625	7,750
Accounts payable	34,681	52,479
Accrued expenses	137,834	182,765
Accrued trade discounts and rebates	501,753	297,556
Accrued royalties—current portion	65,328	61,981
Deferred revenues—current portion	6,885	3,321
Total current liabilities	757,106	605,852
LONG-TERM LIABILITIES:
Exchangeable notes, net	314,384	298,002
Long-term debt, net, net of current	1,576,646	1,501,741
Accrued royalties, net of current	291,185	272,293
Deferred revenues, net of current	9,713	7,763
Deferred tax liabilities, net	157,945	296,568
Other long-term liabilities	68,015	46,061
Total long-term liabilities	2,417,888	2,422,428
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Ordinary shares, $0.0001 nominal value; 300,000,000 shares authorized; 164,785,083 and 162,004,956 shares issued at December 31, 2017 and December 31, 2016, respectively, and 164,400,717 and 161,620,590 shares outstanding at December 31, 2017 and December 31, 2016, respectively	16	16
Treasury stock, 384,366 ordinary shares at December 31, 2017 and December 31, 2016	(4,585)	(4,585)
Additional paid-in capital	2,248,979	2,119,455
Accumulated other comprehensive loss	(983)	(3,086)
Accumulated deficit	(1,252,329)	(848,021)
Total shareholders’ equity	991,098	1,263,779
Total liabilities and shareholders' equity	4,166,092	4,292,059
Developed Technology [Member]
CURRENT ASSETS:
Intangible assets, net	2,443,949	2,767,184
Customer Relationships [Member]
CURRENT ASSETS:
Intangible assets, net	$ 5,441	$ 6,251

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Ordinary shares, nominal value	$ 0.0001	$ 0.0001
Ordinary shares, shares authorized	300,000,000	300,000,000
Ordinary shares, shares issued	164,785,083	162,004,956
Ordinary shares, shares outstanding	164,400,717	161,620,590
Treasury stock, ordinary shares	384,366	384,366

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 1,056,231	$ 981,120	$ 757,044
Cost of goods sold	546,275	393,272	219,502
Gross profit	509,956	587,848	537,542
OPERATING EXPENSES:
Research and development	224,962	60,707	41,865
Selling, general and administrative	677,363	608,308	440,305
Impairment of in-process research and development		66,000
Total operating expenses	902,325	735,015	482,170
Operating (loss) income	(392,369)	(147,167)	55,372
OTHER EXPENSE, NET:
Interest expense, net	(126,523)	(86,610)	(69,900)
Foreign exchange loss	(260)	(1,005)	(1,237)
Gain on divestiture	6,267
Loss on induced conversion of debt and debt extinguishment	(978)		(77,624)
Loss on sale of long-term investments	0	0	(29,032)
Other income (expense), net	588	6,697	(10,291)
Total other expense, net	(120,906)	(80,918)	(188,084)
Loss before benefit for income taxes	(513,275)	(228,085)	(132,712)
Benefit for income taxes	(102,749)	(61,251)	(172,244)
Net (loss) income	$ (410,526)	$ (166,834)	$ 39,532
Net (loss) income per ordinary share—basic	$ (2.52)	$ (1.04)	$ 0.27
Weighted average ordinary shares outstanding—basic	163,122,663	160,699,543	148,788,020
Net (loss) income per ordinary share —diluted	$ (2.52)	$ (1.04)	$ 0.25
Weighted average ordinary shares outstanding—diluted	163,122,663	160,699,543	155,923,251
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX
Foreign currency translation adjustments	$ 2,067	$ (302)	$ 1,712
Pension remeasurements	36	(133)
Other comprehensive income (loss)	2,103	(435)	1,712
Comprehensive (loss) income	$ (408,423)	$ (167,269)	$ 41,244

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2014	$ 540,204	$ 13	$ (4,585)	$ 1,269,858	$ (4,363)	$ (720,719)
Beginning balance, shares at Dec. 31, 2014		124,425,853	384,366
Issuance of ordinary shares, value	475,685	$ 2		475,683
Issuance of ordinary shares		17,652,500
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises	5,217			5,217
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises, shares		1,157,807
Ordinary shares withheld for payment of employees’ withholding tax liability	(3,024)			(3,024)
Issuance of ordinary shares in conjunction with inducement of convertible notes	57,544	$ 1		57,543
Issuance of ordinary shares in conjunction with inducement of convertible notes, Shares		11,368,921
Issuance of ordinary shares in conjunction with ESPP purchases	4,452			4,452
Issuance of ordinary shares in conjunction with ESPP purchases, shares		591,277
Share-based compensation	83,553			83,553
Issuance of ordinary shares in conjunction with warrant exercises	18,124			18,124
Issuance of ordinary shares in conjunction with warrant exercises, shares		4,872,709
Issuance of Exchangeable Senior Notes	119,080			119,080
Deferred tax on Exchangeable Senior Notes	(29,770)			(29,770)
Deferred tax on capped call transactions	836			836
Currency translation adjustment	1,712				1,712
Net (loss) income	39,532					39,532
Ending balance at Dec. 31, 2015	1,313,145	$ 16	$ (4,585)	2,001,552	(2,651)	(681,187)
Ending balance, shares at Dec. 31, 2015		160,069,067	384,366
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises	3,875			3,875
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises, shares		1,245,637
Ordinary shares withheld for payment of employees’ withholding tax liability	(5,539)			(5,539)
Issuance of ordinary shares in conjunction with ESPP purchases	6,540			6,540
Issuance of ordinary shares in conjunction with ESPP purchases, shares		513,659
Issuance of ordinary shares in conjunction with PSU vesting, shares		13,584
Share-based compensation	113,019			113,019
Issuance of ordinary shares in conjunction with warrant exercises	8			8
Issuance of ordinary shares in conjunction with warrant exercises, shares		163,009
Currency translation adjustment	(302)				(302)
Pension remeasurements	(133)				(133)
Net (loss) income	(166,834)					(166,834)
Ending balance at Dec. 31, 2016	1,263,779	$ 16	$ (4,585)	2,119,455	(3,086)	(848,021)
Ending balance, shares at Dec. 31, 2016		162,004,956	384,366
Cumulative effect adjustment from adoption of ASU 2016-09	$ 7,210					7,210
Issuance of ordinary shares	523,520
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises	$ 2,167			2,167
Issuance of ordinary shares in conjunction with vesting of restricted stock units and stock option exercises, shares		1,117,876
Ordinary shares withheld for payment of employees’ withholding tax liability	(6,533)			(6,533)
Issuance of ordinary shares in conjunction with ESPP purchases	7,082			7,082
Issuance of ordinary shares in conjunction with ESPP purchases, shares		822,231
Issuance of ordinary shares in conjunction with PSU vesting, shares		25,000
Share-based compensation	125,019			125,019
Issuance of ordinary shares in conjunction with warrant exercises	1,789			1,789
Issuance of ordinary shares in conjunction with warrant exercises, shares		915,020
Shares repurchased	(992)					(992)
Shares repurchased, shares		(100,000)
Currency translation adjustment	2,067				2,067
Pension remeasurements	36				36
Net (loss) income	(410,526)					(410,526)
Ending balance at Dec. 31, 2017	$ 991,098	$ 16	$ (4,585)	$ 2,248,979	$ (983)	$ (1,252,329)
Ending balance, shares at Dec. 31, 2017		164,785,083,000	384,366,000

Consolidated Statements of Sha6

Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Statement Of Stockholders Equity [Abstract]
Net of the reacquisition of the equity component	$ 243,984

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (410,526)	$ (166,834)	$ 39,532
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization expense	283,415	221,837	138,343
Equity-settled share-based compensation	125,019	113,019	83,553
Royalty accretion	51,263	40,616	20,088
Royalty liability remeasurement	21,774	386	21,151
Acquired in-process research and development expense	159,171
Gain on divestiture	(2,934)
Deferred income taxes	(132,231)	(65,561)	(180,549)
Loss on induced conversions of debt and debt extinguishment	834		21,581
Payments related to term loan refinancing	(3,988)		(3,000)
Amortization of debt discount and deferred financing costs	21,619	18,546	18,810
Impairment of non-current asset	22,270	5,260
Impairment of in-process research and development		66,000
Loss on sale of long-term investments	0	0	29,032
Foreign exchange and other adjustments	(1,466)	420	1,495
Changes in operating assets and liabilities:
Accounts receivable	(61,828)	(67,496)	(124,766)
Inventories	108,371	67,633	12,216
Prepaid expenses and other current assets	5,110	(28,239)	1,014
Accounts payable	(16,521)	32,065	(8,362)
Deferred revenues	4,468	1,114	1,693
Other non-current assets and liabilities	5,720	4,455	8,120
Net cash provided by operating activities	280,208	369,456	194,166
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(167,220)	(1,356,271)	(1,022,361)
Proceeds from divestiture, net of cash divested	69,371
Purchases of property and equipment	(4,334)	(15,731)	(7,156)
Change in restricted cash	564	(3,879)	(1,122)
Proceeds from liquidation of available-for-sale investments			64,623
Purchases of long-term investments			(71,813)
Proceeds from sale of long-term investments			42,781
Net cash used in investing activities	(101,619)	(1,375,881)	(995,048)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from term loans	1,693,512	364,297	391,506
Repayment of term loans	(1,618,617)	(4,000)	(299,000)
Payment of contingent consideration	(20,000)
Repurchase of ordinary shares	(992)
Proceeds from the issuance of ordinary shares in connection with warrant exercises	1,789	8	18,124
Proceeds from the issuance of ordinary shares through an employee stock purchase plan	7,082	6,540	4,452
Proceeds from the issuance of ordinary shares in connection with stock option exercises	2,167	3,875	5,217
Payment of employee withholding taxes relating to share-based awards	(6,533)	(5,539)	(3,024)
Net proceeds from issuance of ordinary shares			475,685
Net cash provided by financing activities	58,408	657,074	1,442,481
Effect of foreign exchange rate changes on cash and cash equivalents	5,316	(1,210)	(790)
Net increase (decrease) in cash and cash equivalents	242,313	(350,561)	640,809
Cash and cash equivalents, beginning of the year	509,055	859,616	218,807
Cash and cash equivalents, end of the year	751,368	509,055	859,616
Supplemental cash flow information:
Cash paid for interest	113,790	60,817	42,021
Cash paid for income taxes	2,548	22,339	1,880
Cash paid for debt extinguishment	145		45,367
Fees paid for debt commitments			9,000
Cash paid for induced conversions			10,005
Supplemental non-cash flow information:
Purchases of acquired in-process research and development included in accounts payable and accrued expenses	12,000
Purchases of property and equipment included in accounts payable and accrued expenses		700	4,940
Conversion of Convertible Senior Notes to ordinary shares			60,985
Accrued Trade Discounts and Rebates [Member]
Changes in operating assets and liabilities:
Accrued liabilities	205,487	112,381	94,046
Accrued Expenses and Accrued Royalties [Member]
Changes in operating assets and liabilities:
Accrued liabilities	(104,819)	13,854	20,169
Exchangeable Senior Notes [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of Exchangeable Senior Notes	$ 387,200		387,181
2024 Senior Notes [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from term loans		$ 291,893
2023 Senior Notes [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from term loans			$ 462,340

Basis of Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	NOTE 1 – BASIS OF PRESENTATION Unless otherwise indicated or the context otherwise requires, references to the “Company”, “we”, “us” and “our” refer to Horizon Pharma plc and its consolidated subsidiaries, including its predecessor, Horizon Pharma, Inc. (“HPI”). During the years ended December 31, 2017, 2016 and 2015, the Company completed the following acquisitions and divestitures: • On June 30, 2017, the Company completed its acquisition of certain rights to interferon gamma-1b from Boehringer Ingelheim International GmbH (“Boehringer Ingelheim International”) in all territories outside of the United States, Canada and Japan. • On June 23, 2017, the Company completed the sale of its European subsidiary that owned the marketing rights to PROCYSBI ® • On May 8, 2017, the Company completed its acquisition of River Vision Development Corp. (“River Vision”), which added the late development-stage rare disease biologic medicine candidate teprotumumab to the Company’s research and development pipeline. • On October 25, 2016, the Company completed its acquisition of Raptor Pharmaceutical Corp. (“Raptor”), which added the rare disease medicines PROCYSBI and QUINSAIR to the Company’s medicine portfolio. • On January 13, 2016 completed its acquisition of ® ® • On May 7, 2015, the Company completed its acquisition of Hyperion Therapeutics, Inc. (“Hyperion”), which added the rare disease medicines RAVICTI ® ® The consolidated financial statements presented herein include the results of operations of the acquired Hyperion, Crealta and Raptor businesses from the applicable dates of acquisition. See Note 4 for further details of business acquisitions and divestitures. Overview The Company is a biopharmaceutical company focused on researching, developing and commercializing innovative medicines that address unmet treatment needs for rare and rheumatic diseases. By fostering a growing pipeline of medicines in development and exploring all potential uses for currently marketed medicines, the Company strives to make a powerful difference for patients, their caregivers and physicians. Orphan Business Unit RAVICTI (glycerol phenylbutyrate) Oral Liquid PROCYSBI (cysteamine bitartrate) delayed-release capsules ACTIMMUNE® (interferon gamma-1b); marketed as IMUKIN® outside the United States, Canada and Japan BUPHENYL (sodium phenylbutyrate) Tablets and Powder; marketed as AMMONAPS® in certain European countries and Japan QUINSAIR (levofloxacin inhalation solution) Rheumatology Business Unit KRYSTEXXA (pegloticase) RAYOS® (prednisone) delayed-release tablets; marketed as LODOTRA® outside the United States Primary Care Business Unit PENNSAID® (diclofenac sodium topical solution) 2% w/w (“PENNSAID 2%”) DUEXIS® (ibuprofen/famotidine) VIMOVO® (naproxen/esomeprazole magnesium) MIGERGOT (ergotamine tartrate & caffeine suppositories) The Company is a public limited company formed under the laws of Ireland. The Company operates through a number of international and U.S. subsidiaries with principal business purposes to either perform research and development or manufacturing operations, serve as distributors of the Company’s medicines, hold intellectual property assets or provide services and financial support to the Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2 – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States of America (“GAAP”). Certain reclassifications have been made to prior-period financial statements to conform to the 2017 presentation. Beginning in the first quarter of 2017, the Company modified its presentation of certain operating expenses. Previously, the Company presented “general and administrative” expenses as one line item in its consolidated statement of comprehensive income (loss), and “selling and marketing” expenses as another. For the year ended December 31, 2017 and prior-period comparisons, the Company now combines these two line items into one line item, titled “selling, general and administrative” expenses. Principles of Consolidation The consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated. Segment Information The Company has determined that it operates in one researching, developing and commercializing innovative medicines that address unmet treatment needs U se of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Foreign Currency Translation and Transactions The reporting currency of the Company and its subsidiaries is the U.S. dollar. The U.S. dollar is the functional currency for the Company’s Ireland and U.S.-based businesses and the majority of its subsidiaries. The Company has foreign subsidiaries that have the Euro and the Canadian Dollar as their functional currency. Foreign currency-denominated assets and liabilities of these subsidiaries are translated into U.S. dollars based on exchange rates prevailing at the end of the period, revenues and expenses are translated at average exchange rates prevailing during the corresponding period, and shareholders’ equity accounts are translated at historical exchange rates as of the date of any equity transaction. The effects of foreign exchange gains and losses arising from the translation of assets and liabilities of those entities where the functional currency is not the U.S. dollar are included as a component of accumulated other comprehensive (loss) income. Gains and losses resulting from foreign currency transactions are reflected within the Company’s results of operations. Revenue Recognition Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the price is fixed or determinable; and collectability is reasonably assured. Some of the Company’s agreements contain multiple elements and in accordance with these agreements, the Company may be eligible for upfront license fees, marketing or commercial milestones and payment for medicine deliveries. Revenue From Medicine Deliveries Revenue from medicine deliveries comprises substantially all of the Company’s gross sales. The Company recognizes revenue from the sale of its medicines when delivery has occurred, title has transferred, the selling price is fixed or determinable, collectability is reasonably assured and the Company has no further performance obligations. In addition, revenue is only recognized when the right of return no longer exists (which is the earlier of the medicine being dispensed through patient prescriptions or the expiration of the right of return) or when medicine returns can be reasonably estimated. Due to the Company’s ability to reasonably estimate and determine allowances for co-pay and other patient assistance, medicine returns, rebates and discounts based on its own internal data for DUEXIS and RAYOS or data relating to prior sales of its acquired medicines which was received in connection with the acquisition of those medicines, the Company recognizes revenue at the point of sale to wholesale pharmaceutical distributors and pharmacies for all currently distributed medicines. Revenue From Upfront License Fees The Company recognizes revenues from the receipt of non-refundable, upfront license fees. In situations where the licensee is able to obtain stand-alone value from the license and no further performance obligations exist on the Company’s part, revenues are recognized on the earlier of when payments are received or collection is reasonably assured. Where continuing involvement by the Company is required in the form of technology transfer, medicine manufacturing or technical support, revenues are deferred and recognized over the term of the agreement. Revenue From Milestone Receipts Milestone payments are recognized as revenue based on achievement of the associated milestones, as defined in the relevant agreements. Revenue from a milestone achievement is recognized when earned, as evidenced by acknowledgment from the Company’s partner, provided that (1) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement, (2) the milestone represents the culmination of an earnings process and (3) the milestone payment is non-refundable. If any of these criteria are not met, revenue from the milestone achievement is recognized over the remaining minimum period of the Company’s performance obligations under the agreement. Medicine Sales Discounts and Allowances The Company records allowances for medicine returns, rebates and discounts at the time of sale to wholesale pharmaceutical distributors and pharmacies. The Company is required to make significant judgments and estimates in determining some of these allowances. If actual results differ from its estimates, the Company will be required to make adjustments to these allowances in the future. Medicine returns and discounts are included in “accounts receivable” on the consolidated balance sheet. Accrued rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Commercial Rebates The Company participates in certain commercial rebate programs. Under these rebate programs, the Company pays a rebate to the commercial entity or third-party administrator of the program. The Company accrues estimated rebates based on contract prices, estimated percentages of medicine sold to qualified patients and estimated levels of inventory in the distribution channel and records the rebate as a reduction of revenue. Accrued commercial rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Distribution Service Fees The Company includes distribution service fees paid to its wholesalers for distribution and inventory management services as a reduction to revenue. The Company accrues estimated distribution fees based on contractually determined amounts, typically as a percentage of revenue. Accrued distribution service fees are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Patient Access Programs The Company offers discount card and other programs such as its HorizonCares program to patients under which the patient receives a discount on his or her prescription. In certain circumstances when a patient’s prescription is rejected by a managed care vendor, the Company will pay for the full cost of the prescription. The Company reimburses pharmacies for this discount through third-party vendors. The Company reduces gross sales by the amount of actual co-pay and other patient assistance in the period based on the invoices received. The Company also records an accrual to reduce gross sales for estimated co-pay and other patient assistance on units sold to distributors that have not yet been prescribed/dispensed to a patient. The estimate is based on contract prices, estimated percentages of medicine that will be prescribed to qualified patients, average assistance paid based on reporting from the third-party vendors and estimated levels of inventory in the distribution channel. Accrued co-pay and other patient assistance fees are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Patient assistance programs include both co-pay assistance and fully bought down prescriptions. Sales Returns Consistent with industry practice, the Company maintains a return policy that allows customers to return medicine within a specified period prior to and subsequent to the medicine expiration date. Generally, medicine may be returned for a period beginning six months prior to its expiration date and up to one year after its expiration date. The right of return expires on the earlier of one year after the medicine expiration date or the time that the medicine is dispensed to the patient. The majority of medicine returns result from medicine dating, which falls within the range set by the Company’s policy, and are settled through the issuance of a credit to the customer. The estimate of the provision for returns is based upon the Company’s historical experience with actual returns, which is applied to the level of sales for the period that corresponds to the period during which the customer may return medicines. This period is known to the Company based on the shelf life of medicines at the time of shipment. The Company records sales returns as an allowance against accounts receivable and a reduction of revenue. Prompt Pay Discounts As an incentive for prompt payment, the Company offers a 2% cash discount to customers. The Company expects that all customers will comply with the contractual terms to earn the discount. The Company records the discount as an allowance against accounts receivable and a reduction of revenue. Government Rebates The Company participates in certain federal government rebate programs, such as Medicare and Medicaid. The Company accrues estimated rebates based on percentages of medicine sold to qualified patients, estimated rebate percentages and estimated levels of inventory in the distribution channel that will be sold to qualified patients and records the rebates as a reduction of revenue. Accrued government rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Government Chargebacks The Company provides discounts to federal government qualified entities with whom the Company has contracted. These federal entities purchase medicines from the wholesale pharmaceutical distributors at a discounted price, and the wholesale pharmaceutical distributors then charge back to the Company the difference between the current retail price and the contracted price that the federal entities paid for the medicines. The Company accrues estimated chargebacks based on contract prices and sell-through sales data obtained from third-party information and records the chargeback as a reduction of revenue. Accrued government chargebacks are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Bad Debt Expense The Company’s medicines are sold to wholesale pharmaceutical distributors and pharmacies. The Company monitors its accounts receivable balances to determine the impact, if any, of such factors as changes in customer concentration, credit risk and the realizability of its accounts receivable, and records a bad debt reserve when applicable. Inventories Inventories are stated at the lower of cost or market value, using the first-in, first-out convention. Inventories consist of raw materials, work-in-process and finished goods. The Company has entered into manufacturing and supply agreements for the manufacture or purchase of raw materials and production supplies. The Company’s inventories include the direct purchase cost of materials and supplies and manufacturing overhead costs. The Company reviews its inventory balance and purchase obligations to assess if it has obsolete or excess inventory and records a charge to “cost of goods sold” when applicable. Inventories acquired in business combinations are recorded at their estimated fair values. “Step-up” represents the write-up of inventory from the lower of cost or market value (the historical book value as previously recorded on the acquired company’s balance sheet) to fair market value at the acquisition date. Inventory step-up expense is recorded in the consolidated statement of comprehensive (loss) income based on actual sales, or usage, using the first-in, first-out convention. Inventories exclude medicine sample inventory, which is included in other current assets and is expensed as a component of “selling, general and administrative” expense when shipped to sales representatives. Cost of Goods Sold The Company recognizes cost of goods sold in connection with its sales of each of its distributed medicines. Cost of goods sold includes all costs directly related to the acquisition of the Company’s medicines from its third-party manufacturers, including freight charges and other direct expenses such as insurance and supply chain costs. Cost of goods sold also includes amortization of intellectual property as described in the intangible assets accounting policy below, inventory step-up expense, drug substance harmonization costs, share-based compensation, charges relating to discontinuation of clinical trials, royalty payments to third parties, royalty accretion expense, changes in estimates associated with the contingent royalty liability as described in the accrued contingent royalty accounting policy below and loss on inventory purchase commitments. Pre-clinical Studies and Clinical Trial Accruals The Company’s pre-clinical studies and clinical trials have historically been conducted by third-party contract research organizations and other vendors. Pre-clinical study and clinical trial expenses are based on the services received from these contract research organizations and vendors. Payments depend on factors such as the milestones accomplished, successful enrollment of certain numbers of patients and site initiation. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual accordingly. Net (Loss) Income Per Share Basic net (loss) income per share is computed by dividing net (loss) income by the weighted-average number of ordinary shares outstanding during the period. Diluted earnings per share (“EPS”) reflects the potential dilution beyond shares for basic EPS that could occur if securities or other contracts to issue ordinary shares were exercised, converted into ordinary shares, or resulted in the issuance of ordinary shares that would have shared in the Company’s earnings. Cash and Cash Equivalents The Company considers all highly liquid investments, readily convertible to cash, that mature within three months or less from date of purchase to be cash equivalents . Restricted Cash Restricted cash consists primarily of balances in interest-bearing money market accounts required by a vendor for the Company’s sponsored employee business credit card program and collateral for a letter of credit. Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, approximate their fair values due to their short maturities. Business Combinations The Company accounts for business combinations in accordance with the guidance in Accounting Standards Codification Topic 805 , Business Combinations Provision for Income Taxes The Company accounts for income taxes based upon an asset and liability approach. Deferred tax assets and liabilities represent the future tax consequences of the differences between the financial statement carrying amounts of assets and liabilities versus the tax basis of assets and liabilities. Under this method, deferred tax assets are recognized for deductible temporary differences, and operating loss and tax credit carryforwards. Deferred tax liabilities are recognized for taxable temporary differences. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The impact of tax rate changes on deferred tax assets and liabilities is recognized in the year that the change is enacted. The Company also accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or are expected to be taken on an income tax return. Deferred tax assets and deferred tax liabilities are netted by jurisdiction on the Company’s consolidated balance sheets. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) which provides guidance on accounting for the tax effects of the U.S. H.R. 1, “An Act to provide for reconciliation pursuant to titles II and V of the concurrent resolution on the budget for fiscal year 2018”, informally titled the Tax Cuts and Jobs Act (“the Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the date of enactment for companies to complete the accounting under ASC Topic 740, Income Taxes However, the Company has made reasonable estimates of the effects on its income tax provision with respect to certain items, primarily the revaluation of its existing U.S. deferred tax balances and the write-off of its U.S. deferred tax assets resulting from interest expense carryforwards under Section 163(j) of the Internal Revenue Code. In other cases, the Company has not been able to make reasonable estimates and continues to account for those items based on its existing accounting under the provisions of the tax laws that were in effect prior to enactment of the Tax Act. Property and Equipment, Net Property and equipment are stated at cost less accumulated depreciation. Depreciation is recognized using the straight-line method over the estimated useful lives of the related assets for financial reporting purposes and an accelerated method for income tax reporting purposes. Upon retirement or sale of an asset, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations. Repair and maintenance costs are charged to expenses as incurred and improvements are capitalized. Leasehold improvements are amortized on a straight-line basis over the term of the applicable lease, or the useful life of the assets, whichever is shorter. Depreciation and amortization periods for the Company’s property and equipment are as follows: Machinery and equipment 5 to 7 years Furniture and fixtures 3 to 5 years Computer equipment 3 years Software 3 years Trade show equipment 3 years The Company capitalizes software development costs associated with internal use software, including external direct costs of materials and services and payroll costs for employees devoting time to a software project. Costs incurred during the preliminary project stage, as well as costs for maintenance and training, are expensed as incurred. Software includes internal-use software acquired and modified to meet the Company’s internal requirements. Amortization commences when the software is ready for its intended use. Intangible Assets Definite-lived intangible assets are amortized over their estimated useful lives. The Company reviews its intangible assets when events or circumstances may indicate that the carrying value of these assets exceeds their fair value. The Company measures fair value based on the estimated future discounted cash flows associated with these assets in addition to other assumptions and projections that the Company deems to be reasonable and supportable. The estimated useful lives, from the date of acquisition, for all identified intangible assets that are subject to amortization are between five and thirteen years. The Company determined that no impairment of its definite-lived intangible assets existed as of December 31, 2017. Indefinite-lived intangible assets consist of capitalized in-process research and development (“IPR&D”). IPR&D assets represent capitalized incomplete research projects that the Company acquired through business combinations. Such assets are initially measured at their acquisition date fair values and are tested for impairment, until completion or abandonment of research and development efforts associated with the projects. An IPR&D asset is considered abandoned when research and development efforts associated with the asset have ceased, and there are no plans to sell or license the asset or derive value from the asset. At that point, the asset is considered to be impaired and is written off. Upon successful completion of each project, the Company will make a determination about the then remaining useful life of the intangible asset and begin amortization. The Company tests its indefinite-lived intangible assets, including IPR&D assets, for impairment annually during the fourth quarter and more frequently if events or changes in circumstances indicate that it is more likely than not that the asset is impaired. Following an impairment charge recorded in the fourth quarter of 2016, the Company had no indefinite-lived intangible assets as of December 31, 2017 and 2016. See Note 8 for further details of the impairment charge. Goodwill Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value of the identifiable net assets acquired. Goodwill is not amortized but is tested for impairment at least annually at the reporting unit level or more frequently if events or changes in circumstances indicate that the asset might be impaired. Impairment loss, if any, is recognized based on a comparison of the fair value of the asset to its carrying value, without consideration of any recoverability. The Company tests goodwill for impairment annually during the fourth quarter and whenever indicators of impairment exist by first assessing qualitative factors to determine whether it is more likely than not that the fair value is less than its carrying amount. If the Company concludes it is more likely than not that the fair value of a reporting unit is less than its carrying amount, a quantitative impairment test is performed. If the Company concludes that goodwill is impaired, it will record an impairment charge in its consolidated statement of comprehensive (loss) income. Based upon the Company’s most recent annual impairment test performed in the fourth quarter of 2017, the Company concluded goodwill was not impaired. Research and Development Expenses Research and development expenses include, but are not limited to, payroll and other personnel expenses, consultant expenses, expenses incurred under agreements with contract research organizations to conduct clinical trials, expenses incurred to manufacture clinical trial materials and acquired in-process research and development assets recorded to research and development expense. Research and development expenses were $225.0 million, $60.7 million and $41.9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Advertising Expenses We expense the costs of advertising as incurred. Advertising expenses were $19.2 million, $14.4 million and $6.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. Deferred Financing Costs Costs incurred in connection with debt financings have been capitalized to “Long-term debt, net, net of current” and “Exchangeable notes, net” in the Company’s consolidated balance sheets as deferred financing costs, and are charged to interest expense using the effective interest method over the terms of the related debt agreements. These costs include document preparation costs, commissions, fees and expenses of investment bankers and underwriters, and accounting and legal fees. Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that may potentially subject the Company to significant concentrations of credit risk consist of cash and cash equivalents. The Company’s cash and cash equivalents are invested primarily in money market funds and bank deposits in the United States, Bermuda, Ireland, Switzerland, Luxembourg, Germany, the United Kingdom and Canada that management believes are creditworthy. At times, deposits in these banks may exceed the amount of insurance provided on such deposits. To date, the Company has not experienced any losses on its investments of cash and cash equivalents. The purchase cost of ACTIMMUNE under a contract with Boehringer Ingelheim RCV GmbH & Co. KG (“Boehringer Ingelheim”) as well as sales contracts relating to LODOTRA and QUINSAIR, and sales of RAVICTI and PROCYSBI outside the United States, are principally denominated in Euros or the Canadian dollar and are subject to foreign currency risk. The Company also incurs certain operating expenses in currencies other than the U.S. dollar in relation to its operations and foreign subsidiaries in Ireland, Switzerland, Germany and Canada. The Company does not currently utilize and has not in the past utilized any foreign currency hedging strategies to mitigate the effect of its foreign currency exchange rate risk. Historically, the Company’s accounts receivable balances have been highly concentrated with a select number of customers, consisting primarily of large wholesale pharmaceutical distributors who, in turn, sell the medicines to pharmacies, hospitals and other customers. As of December 31, 2017 and 2016, the Company’s top three customers accounted for approximately 79% and 78%, respectively, of the Company’s total outstanding accounts receivable balances. The Company depends on single-source suppliers and manufacturers for certain of its medicines, medicine candidates and their active pharmaceutical ingredients. Comprehensive (Loss) Income Comprehensive (loss) income is composed of net (loss) income and other comprehensive (loss) income (“OCI”). OCI includes certain changes in shareholders’ equity that are excluded from net (loss) income, which consist of foreign currency translation adjustments and pension remeasurements. The Company reports the effect of significant reclassifications out of accumulated OCI on the respective line items in net income if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income in the same reporting period, the Company cross-references other disclosures required under GAAP that provide additional detail about those amounts. Share-Based Compensation The Company accounts for employee share-based compensation by measuring and recognizing compensation expense for all share-based payments based on estimated grant date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over each awardee’s requisite service period, which is generally the vesting period. The Company adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting Accrued Contingent Royalties The Company’s accrued contingent royalties consist of the contingent royalty obligations assumed by the Company related to the Company’s acquisitions of rights to certain of its medicines. At the time of each acquisition, the Company assigned an estimated fair value to its contingent liability for royalties. The estimated royalty liability is based on anticipated revenue streams utilizing the income approach under the discounted cash flow method. The estimated liability for royalties is increased or decreased over time to reflect the change in its present value and accretion expense is recorded as part of cost of goods sold. The Company evaluates the adequacy of the estimated contingent royalty liability at least annually in the fourth quarter, or whenever events or changes in circumstances indicate that an evaluation of the estimate is necessary. As part of its evaluation, the Company adjusts the carrying value of the liability to the present value of the revised estimated cash flows using the original discount rate. Any adjustment to the liability is recorded as an increase or reduction in cost of goods sold. The royalty liability is included in current and long-term accrued royalties on the consolidated balance sheets. Contingencies From time to time, the Company may become involved in claims and other legal matters arising in the ordinary course of business. The Company records accruals for loss contingencies to the extent that it concludes that it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. Legal fees and other expenses related to litigation are expensed as incurred and included in “selling, general and administrative” expenses. Recent Accounting Pronouncements From time to time, the Company adopts new accounting pronouncements issued by the Financial Accounting Standards Board (“FASB”) or other standard-setting bodies. Effective January 1, 2017, the Company elected to early adopt ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business Effective January 1, 2017, the Company adopted ASU No. 2016-09. The update requires excess tax benefits and tax deficiencies, which arise due to differences between the measure of compensation expense and the amount deductible for tax purposes, to be recorded directly through earnings as a component of income tax expense. Previously, these differences were generally recorded in additional paid-in capital and thus had no impact on net income. The change in treatment of excess tax benefits and tax deficiencies also impacts the computation of diluted earnings per share, and the cash flows associated with those items are classified as operating activities on the consolidated statements of cash flows. Additionally, ASU No. 2016-09 permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated, as allowed under previous standards, or recognized when they occur. As a result of the adoption, $7.2 million of excess tax benefits that had not previously been recognized, as the related tax deduction had not reduced current taxes payable, were recorded on a modified retrospective basis through a cumulative effect adjustment to its accumulated deficit as of January 1, 2017. During the year ended December 31, 2017, the Company recognized an excess tax deficiency in earnings of $2.8 million. The Company elected not to change its policy on accounting for forfeitures and continues to estimate a requisite forfeiture rate. Additional amendments to the accounting for income taxes and minimum statutory withholding requirements had no impact on the Company’s results of operations and related disclosures. In May 2014, the FASB issued ASU Revenue from Contracts with Customers , Revenue From Contracts With Customers, , Revenue Recognition. In October 2016, the FASB issued ASU No. Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting , Compensation- Stock Compensation. In February 2017, the FASB issued ASU No. 2017-05, (“ Subtopic 610-20 , Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Topic 220), (“ASU No. 2018-02”), which permits a company to reclassify the income tax effects of the Tax Act on items within other comprehensive income (“OCI”) to retained earnings. ASU No. 2018-02 requires certain new disclosures, some of which are applicable for all companies and is effective for fiscal years beginning after December 15, 2018, a

Net (Loss) Income per Share

Net (Loss) Income per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net (Loss) Income per Share	NOTE 3 – NET (LOSS) INCOME PER SHARE The following table presents basic net (loss) income per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except share and per share data): For the Years Ended December 31, 2017 2016 2015 Basic earnings per share calculation: Net (loss) income $ (410,526 ) $ (166,834 ) $ 39,532 Weighted average of ordinary shares outstanding 163,122,663 160,699,543 148,788,020 Basic net (loss) income per share $ (2.52 ) $ (1.04 ) $ 0.27 The following table presents diluted net (loss) income per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except share and per share data): For the Years Ended December 31, 2017 2016 2015 Diluted earnings per share calculation: Net (loss) income $ (410,526 ) $ (166,834 ) $ 39,532 Weighted average of ordinary shares outstanding 163,122,663 160,699,543 155,923,251 Diluted net (loss) income per share $ (2.52 ) $ (1.04 ) $ 0.25 Basic net (loss) income per share is computed by dividing net (loss) income by the weighted-average number of ordinary shares outstanding during the period. Diluted net (loss) income per share reflects the potential dilution beyond shares for basic net (loss) income per share that could occur if securities or other contracts to issue ordinary shares were exercised, converted into ordinary shares, or resulted in the issuance of ordinary shares that would have shared in the Company’s earnings. The outstanding securities listed in the table below were excluded from the computation of diluted (loss) income per ordinary share for the years ended December 31, 2017, 2016 and 2015 due to being anti-dilutive: For the Years Ended December 31, 2017 2016 2015 Stock options 12,887,595 7,515,297 2,853,821 Restricted stock units 1,095,768 492,030 817,168 Performance stock units 2,742,301 5,247,987 1,074 Employee stock purchase plan 63,445 56,805 1,046,275 Warrants 388,841 1,123,737 2,416,894 17,177,950 14,435,856 7,135,232 The potentially dilutive impact of the March 2015 private placement of $400.0 million aggregate principal amount of 2.50% Exchangeable Senior Notes due 2022 (the “Exchangeable Senior Notes”) by Horizon Pharma Investment Limited (“Horizon Investment”), a wholly owned subsidiary of the Company, is determined using a method similar to the treasury stock method. Under this method, no numerator or denominator adjustments arise from the principal and interest components of the Exchangeable Senior Notes because the Company has the intent and ability to settle the Exchangeable Senior Notes’ principal and interest in cash. Instead, the Company is required to increase the diluted net (loss) income per share denominator by the variable number of shares that would be issued upon conversion if it settled the conversion spread obligation with shares. For diluted net (loss) income per share purposes, the conversion spread obligation is calculated based on whether the average market price of the Company’s ordinary shares over the reporting period is in excess of the exchange price of the Exchangeable Senior Notes. There was no calculated spread added to the denominator for the years ended December 31, 2017, 2016 and 2015.

Acquisitions, Divestitures and

Acquisitions, Divestitures and Other Arrangements	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions, Divestitures and Other Arrangements	NOTE 4 –ACQUISITIONS, DIVESTITURES AND OTHER ARRANGEMENTS Acquisitions Acquisition of River Vision On May 8, 2017, the Company acquired 100% of the equity interests in River Vision for upfront cash payments totaling approximately $150.3 million, including cash acquired of $6.3 million, with additional potential future milestone and royalty payments contingent on the satisfaction of certain regulatory milestones and sales thresholds. Pursuant to ASC 805 (as amended by ASU No. 2017-01), the Company accounted for the River Vision acquisition as the purchase of an in-process research and development (“IPR&D”) asset and, pursuant to ASC Topic 730, Research and Development, Acquisition of Additional Rights to Interferon Gamma-1b On June 30, 2017, the Company completed its acquisition of certain rights to interferon gamma-1b from Boehringer Ingelheim International in all territories outside of the United States, Canada and Japan, as the Company previously held marketing rights to interferon gamma-1b in these territories. Boehringer Ingelheim International commercialized interferon gamma-1b as IMUKIN in an estimated thirty countries, primarily in Europe and the Middle East. In May 2016, the Company paid Boehringer Ingelheim International €5.0 million ($5.6 million when converted using a Euro-to-Dollar exchange rate at date of payment of 1.1132) for such rights and upon closing in June 2017, the Company paid Boehringer Ingelheim International an additional €19.5 million ($22.3 million when converted using a Euro-to-Dollar exchange rate at date of payment of 1.1406). The Company currently markets interferon gamma-1b as ACTIMMUNE in the United States. The €5.0 million upfront amount paid in May 2016 had initially been included in “other assets” in the Company’s consolidated balance sheet. Following the discontinuation of the Friedreich’s ataxia (“FA”) program in December 2016, the Company recorded an impairment charge of €5.0 million ($5.3 million when converted using a Euro-to-Dollar exchange rate at date of impairment of 1.052) to fully write off the asset in its consolidated statements of comprehensive loss during the year ended December 31, 2016 as projections for future net sales of IMUKIN in these territories did not exceed the related costs. Upon closing, during the year ended December 31, 2017, the Company accounted for the additional €19.5 million payment ($22.3 million when converted using a Euro-to-Dollar exchange rate at date of payment of 1.1406) as the acquisition of an asset which was immediately impaired, and recorded the payment as a “selling, general and administrative” expense in its consolidated statement of comprehensive loss. Acquisition of Raptor On October 25, 2016, the Company completed its acquisition of Raptor in which the Company acquired all of the issued and outstanding shares of Raptor’s common stock for $9.00 per share. The acquisition added two medicines, PROCYSBI and QUINSAIR, to the Company’s medicine portfolio. Following completion of the acquisition, Raptor became a wholly owned subsidiary of the Company and converted to a limited liability company, changing its name to Horizon Pharmaceutical LLC. The Company financed the transaction through $300.0 million of aggregate principal amount of 8.75% Senior Notes due 2024 (the “2024 Senior Notes”), $375.0 million aggregate principal amount of loans pursuant to an amendment to the Company’s existing credit agreement, as described in Note 16, and cash on hand. The total consideration for the acquisition was approximately $860.8 million, including cash acquired of $24.9 million and $56.0 million paid to settle Raptor’s outstanding debt, and was composed of the following (in thousands): Cash $ 841,494 Net settlements on the exercise of stock options and restricted stock units 19,268 Total consideration $ 860,762 During the year ended December 31, 2016, the Company incurred $15.7 million, in Raptor acquisition-related transaction costs including advisory, legal and other professional and consulting fees, which were recorded for as “selling, general and administrative” expenses in the consolidated statement of comprehensive loss. Pursuant to ASC 805, the Company accounted for the Raptor acquisition as a business combination using the acquisition method of accounting. Identifiable assets and liabilities of Raptor, including identifiable intangible assets, were recorded based on their estimated fair values as of the date of the closing of the acquisition. The excess of the purchase price over the fair value of the net assets acquired was recorded as goodwill. Significant judgment was required in determining the estimated fair values of developed technology intangible assets, inventories and certain other assets and liabilities. Such valuation required estimates and assumptions including, but not limited to, estimating future cash flows and direct costs in addition to developing the appropriate discount rates and current market profit margins. The Company’s management believes the fair values recognized for the assets acquired and the liabilities assumed were based on reasonable estimates and assumptions. During the year ended December 31, 2017, the Company recorded measurement period adjustments related to accrued expenses, accrued trade discounts and rebates and deferred tax liabilities as a result of new information regarding facts existing at the acquisition date, resulting in a net decrease to goodwill of $2.9 million. The following table summarizes the preliminary fair values assigned to the assets acquired and the liabilities assumed by the Company, along with the resulting goodwill before and after the measurement period adjustments (in thousands): (Liabilities assumed) and assets acquired: Preliminary Adjustment Final Accounts payable and accrued expenses $ (28,345 ) $ (240 ) $ (28,585 ) Accrued trade discounts and rebates (6,377 ) 1,350 (5,027 ) Deferred tax liabilities (237,166 ) 1,743 (235,423 ) Contingent and accrued royalties (104,705 ) (104,705 ) Other non-current liability (25,500 ) (25,500 ) Cash and cash equivalents 24,897 24,897 Restricted cash 1,350 1,350 Accounts receivable, net 17,767 17,767 Inventories 74,463 74,463 Prepaid expenses and other current assets 4,194 4,194 Property and equipment 3,373 3,373 Developed technology 946,000 946,000 Other non-current assets 1,765 1,765 Goodwill 189,046 (2,853 ) 186,193 Fair value of consideration paid $ 860,762 $ — $ 860,762 Inventories acquired included raw materials, work-in-process and finished goods for PROCYSBI and QUINSAIR. Inventories were recorded at their estimated fair values. The fair value of finished goods was determined based on the estimated selling price, net of selling costs and a margin on the selling costs. The fair value of work-in-process was determined based on estimated selling price, net of selling costs and costs to complete the manufacturing, and a margin on the selling and manufacturing costs. The fair value of raw materials was estimated to equal the replacement cost. A step-up in the value of inventory of $67.0 million was recorded in connection with the acquisition. During the year ended December 31, 2017, the Company recorded inventory step-up expense of $44.0 million, related to PROCYSBI and QUINSAIR, of which $3.2 million was recorded to “gain on divestiture” in the consolidated statement of comprehensive loss during the year ended December 31, 2017. During the year ended December 31, 2016, the Company recorded inventory step-up expense of $22.4 million related to PROCYSBI and QUINSAIR. As at December 31, 2017 inventory step-up relating to PROCYSBI has been fully expensed. Other tangible assets and liabilities were valued at their respective carrying amounts as management believes that these amounts approximated their acquisition date fair values. Other non-current liability of $25.5 million represents the fair value of an assumed contingent liability arising from contingent payments associated with development, regulatory and commercial milestones following Raptor’s acquisition of QUINSAIR. During the year ended December 31, 2017, the Company paid $20.0 million relating to milestones in connection with this assumed contingent consideration liability. Identifiable intangible assets and liabilities acquired include developed technology and contingent royalties. The estimated fair values of the developed technology and contingent royalties represent valuations performed with the assistance of an independent appraisal firm based on management’s estimates, forecasted financial information and reasonable and supportable assumptions. Developed technology intangible assets reflect the estimated fair value of Raptor’s rights to PROCYSBI. The fair value of developed technology was determined using an income approach. The income approach explicitly recognizes that the fair value of an asset is premised upon the expected receipt of future economic benefits such as earnings and cash inflows based on current sales projections and estimated direct costs for Raptor’s medicines. Indications of value were developed by discounting these benefits to their acquisition-date worth at a discount rate of 12.5%. The fair value of the PROCYSBI developed technology was capitalized as of the Raptor acquisition date and is subsequently being amortized over approximately thirteen years and nine years for the U.S. rights and ex-U.S. rights, respectively, which are the periods in which over 90% of the estimated cash flows are expected to be realized. The Company assigned no fair value to QUINSAIR developed technology as projections of future net sales do not exceed the related costs. See Note 8 for details of developed technology sold in the Chiesi divestiture. The Company assigned a fair value of $102.0 million to a contingent liability for royalties potentially payable under previously existing agreements related to PROCYSBI. The royalties for PROCYSBI are payable under the terms of an amended and restated license agreement with The Regents of the University of California, San Diego (“UCSD”). See Note 18 for details of the percentages of royalties payable under this agreement. The initial fair value of this liability was determined using a discounted cash flow analysis incorporating the estimated future cash flows of royalty payments resulting from future sales. The discount rate used was the same as for the fair value of the developed technology. Deferred tax assets and liabilities arise from acquisition accounting adjustments where book values of certain assets and liabilities differ from their tax bases. Deferred tax assets and liabilities are recorded at the currently enacted rates which will be in effect at the time when the temporary differences are expected to reverse in the country where the underlying assets and liabilities are located. Raptor’s developed technology as of the acquisition date was located primarily in the United States where a U.S. tax rate of 36.6% was used and a significant deferred tax liability was recorded. Goodwill represents the excess of the acquisition consideration over the estimated fair value of net assets acquired and was recorded in the consolidated balance sheet as of the acquisition date. The Company does not expect any portion of this goodwill to be deductible for tax purposes. Acquisition of Crealta On January 13, 2016, the Company completed its acquisition of all the membership interests of Crealta. The acquisition added two medicines, KRYSTEXXA and MIGERGOT, to the Company’s medicine portfolio. The total consideration for the acquisition was approximately $539.7 million, including cash acquired of $24.9 million and $70.9 million paid to settle Crealta’s outstanding debt, and was composed of the following (in thousands): Before Adjustments After Cash $ 536,181 $ 25 $ 536,206 Net settlements on the exercise of stock options and restricted units 3,526 — 3,526 Total consideration $ 539,707 $ 25 $ 539,732 During the years ended December 31, 2016 and 2015, the Company incurred $3.5 million and $1.9 million, respectively, in Crealta acquisition-related transaction costs including investment advisory costs, legal and other professional and consulting fees, which were accounted for as “selling, general and administrative” expenses in the consolidated statements of comprehensive (loss) income. Pursuant to ASC 805, the Company accounted for the Crealta acquisition as a business combination using the acquisition method of accounting. Identifiable assets and liabilities of Crealta, including identifiable intangible assets, were recorded based on their estimated fair values as of the date of the closing of the acquisition. The excess of the purchase price over the fair value of the net assets acquired was recorded as goodwill. Significant judgment was required in determining the estimated fair values of developed technology intangible assets, inventories and certain other assets and liabilities. Such valuation required estimates and assumptions including, but not limited to, estimating future cash flows and direct costs in addition to developing the appropriate discount rates and current market profit margins. The Company’s management believes the fair values recognized for the assets acquired and the liabilities assumed were based on reasonable estimates and assumptions. During the year ended December 31, 2016, the Company recorded measurement period adjustments related to developed technology, inventory and deferred tax liabilities, which adjustments resulted in a net increase in goodwill of $8.1 million. The measurement period adjustments were the result of an adjustment for inventory that was subsequently discovered to have been damaged and defective as of the acquisition date, a net working capital true-up adjustment and the alignment of Crealta’s inventory and obsolescence reserve policy to the Company’s policy. The following table summarizes the preliminary fair values assigned to the assets acquired and the liabilities assumed by the Company along with the resulting goodwill before and after the measurement period adjustments (in thousands): (Liabilities assumed) and assets acquired: Preliminary Adjustment Final Accounts payable and accrued expenses $ (4,543 ) $ — $ (4,543 ) Accrued trade discounts and rebates (1,424 ) — (1,424 ) Deferred tax liabilities (20,835 ) 694 (20,141 ) Other non-current liabilities (6,900 ) — (6,900 ) Contingent royalty liabilities (51,300 ) — (51,300 ) Cash and cash equivalents 24,893 — 24,893 Accounts receivable 10,014 — 10,014 Inventories 169,054 (19,691 ) 149,363 Prepaid expenses and other current assets 1,382 — 1,382 Developed technology 417,300 10,900 428,200 Other non-current assets 275 — 275 Goodwill 1,791 8,122 9,913 Fair value of consideration paid $ 539,707 $ 25 $ 539,732 Inventories acquired included raw materials, work-in-process and finished goods for KRYSTEXXA and MIGERGOT. Inventories were recorded at their preliminary estimated fair values. The fair value of finished goods was determined based on the estimated selling price, net of selling costs and a margin on the selling costs. The fair value of work-in-process was determined based on estimated selling price, net of selling costs and costs to complete the manufacturing, and a margin on the selling and manufacturing costs. The fair value of raw materials was estimated to equal the replacement cost. A step-up in the value of inventory of $144.3 million was recorded in connection with the acquisition. During the year ended December 31, 2017, the Company recorded inventory step-up expense of $78.3 million related to KRYSTEXXA. Other tangible assets and liabilities were valued at their respective carrying amounts as management believes that these amounts approximated their acquisition date fair values. Other non-current liabilities represented an assumed $6.9 million probable contingent liability which was released to “other income (expense)” in the consolidated statement of comprehensive loss during the year ended December 31, 2016. Identifiable intangible assets and liabilities acquired include developed technology and contingent royalties. The estimated fair values of the developed technology and contingent royalties represent valuations performed with the assistance of an independent appraisal firm based on management’s estimates, forecasted financial information and reasonable and supportable assumptions. Developed technology intangible assets reflect the estimated fair value of Crealta’s rights to its currently marketed medicines, KRYSTEXXA and MIGERGOT. The fair value of developed technology was determined using an income approach. The income approach explicitly recognizes that the fair value of an asset is premised upon the expected receipt of future economic benefits such as earnings and cash inflows based on current sales projections and estimated direct costs for Crealta’s medicines. Indications of value were developed by discounting these benefits to their acquisition-date worth at a discount rate of 27% for KRYSTEXXA and 23% for MIGERGOT. The fair value of the KRYSTEXXA and MIGERGOT developed technologies were capitalized as of the Crealta acquisition date and are subsequently being amortized over approximately twelve and ten years, respectively, which are the periods in which over 90% of the estimated cash flows are expected to be realized. The Company has assigned a fair value of $51.3 million to a contingent liability for royalties potentially payable under previously existing agreements related to KRYSTEXXA and MIGERGOT. The royalties for KRYSTEXXA are payable under the terms of a license agreement with Duke University (“Duke”) and Mountain View Pharmaceuticals (“MVP”). See Note 18 for details of the percentages of royalties payable under such agreements. The initial fair value of this liability was determined using a discounted cash flow analysis incorporating the estimated future cash flows of royalty payments resulting from future sales. The discount rate used was the same as for the fair value of the developed technology. The deferred tax liability recorded represents deferred tax liabilities assumed as part of the acquisition, net of deferred tax assets, related to net operating tax loss carryforwards of Crealta. Goodwill represents the excess of the acquisition consideration over the estimated fair value of net assets acquired and was recorded in the consolidated balance sheet as of the acquisition date. The Company does not expect any portion of this goodwill to be deductible for tax purposes. Divestiture of PROCYSBI and QUINSAIR rights in EMEA Regions On June 23, 2017, the Company completed the Chiesi divestiture for an upfront payment of $72.5 million, which reflects $3.1 million of cash divested, with additional potential milestone payments based on sales thresholds. Pursuant to ASU No. 2017-01, the Company accounted for the Chiesi divestiture as a sale of a business. The Company determined that the sale of the business and its assets in connection with the Chiesi divestiture did not constitute a strategic shift and that it did not and will not have a major effect on its operations and financial results. Accordingly, the operations associated with the Chiesi divestiture are not reported in discontinued operations. The gain on divestiture was determined as follows (in thousands): For the Year Ended December 31, 2017 Cash proceeds $ 72,462 Add reimbursement of royalties 27,101 Less net assets sold: Developed technology (47,261 ) Goodwill (16,285 ) Other (24,482 ) Transaction and other costs (5,268 ) Gain on divestiture $ 6,267 Under the terms of its agreement with Chiesi, the Company will continue to pay third parties for the royalties on sales of PROCYSBI and QUINSAIR in EMEA, and Chiesi will reimburse the Company for those royalties. At the date of divestiture, the Company recorded an asset of $27.1 million to “other assets”, which represented the estimated amounts that are expected to be reimbursed from Chiesi for the PROCYSBI and QUINSAIR royalties. These estimated royalties are accrued in “accrued expenses” and “other long-term liabilities”. Transaction and other costs primarily relate to professional and license fees attributable to the divestiture. Other Arrangements Collaboration and option agreement On November 8, 2016, the Company entered into a collaboration and option agreement with a privately held life-science entity. Under the terms of the agreement, the privately held life-science entity will conduct certain research and pre-clinical and clinical development activities. Upon execution of the agreement, the Company paid $0.1 million for the option to acquire certain assets of the privately held life-science entity for $25.0 million, which is exercisable on specified key dates. Under the collaboration and option agreement, the Company is required to pay up to $9.8 million upon the attainment of various milestones, primarily to fund clinical development costs for the medicine candidate. The initial upfront amount paid of $0.1 million has been included in “other assets” in the Company’s consolidated balance sheet as of December 31, 2017 and 2016. During the years ended December 31, 2017 and 2016, $1.5 million and $1.1 million, respectively, was recorded as “research and development” expenses in the consolidated statement of comprehensive loss related to milestones. The Company has determined that the privately held life-science entity is a variable interest entity (“VIE”) as it does not have enough equity to finance its activities without additional financial support. As the Company does not have the power to direct the activities of the VIE that most significantly affect its economic performance, it is not the primary beneficiary of, and does not consolidate the financial results of the VIE. The Company will reassess the appropriate accounting treatment for this arrangement throughout the life of the agreement and modify these accounting conclusions accordingly. Licensing agreement On December 12, 2017, the Company entered into an agreement to license HZN-003 (formerly MEDI4945), a potential next-generation biologic for uncontrolled gout, from MedImmune LLC (“MedImmune”), the global biologics research and development arm of the AstraZeneca Group. HZN-003 is a pre-clinical, genetically engineered uricase derivative with optimized uricase and optimized PEGylation technology that has the potential to improve the response rate to the biologic as well as the potential for subcutaneous dosing. Under the terms of the agreement, the Company agreed to pay MedImmune an upfront cash payment of $12.0 million with additional potential future milestone payments of up to $153.5 million contingent on the satisfaction of certain development and sales thresholds. The $12.0 million upfront payment was accounted for as the acquisition of an asset and was recorded as “research and development” expenses in the consolidated statement of comprehensive loss during the year ended December 31, 2017 and included in “accrued expenses” as of December 31, 2017. The upfront payment was subsequently paid in January 2018. Pro Forma Information (Unaudited) The following table represents consolidated financial information for the Company on a pro forma basis. The pro forma adjustments assume that the Crealta and Raptor acquisitions occurred as of January 1, 2015 and the Hyperion acquisition occurred as of January 1, 2014. The results of Raptor from October 25, 2016 to December 31, 2016 and the results of Crealta from January 13, 2016 to December 31, 2016 are included in the 2016 as reported figures and the results of Hyperion from May 7, 2015 to December 31, 2016 are included in the 2015 and 2016 as reported figures. The historical financial information has been adjusted to give effect to pro forma items that are directly attributable to the Hyperion, Crealta and Raptor acquisitions, and are expected to have a continuing impact on the consolidated results. These items include, among others, adjustments to record the amortization of definite-lived intangible assets, interest expense, debt discount and deferred financing costs associated with the debt in connection with the acquisitions. Additionally, the following table sets forth unaudited financial information and has been compiled from historical financial statements and other information, but is not necessarily indicative of the results that actually would have been achieved had the transactions occurred on the dates indicated or that may be achieved in the future (in thousands, except per share data): For the Year Ended December 31, 2016 2015 As reported Pro forma adjustments Pro forma As reported Pro forma adjustments Pro forma Net sales $ 981,120 $ 109,298 $ 1,090,418 $ 757,044 $ 200,611 $ 957,655 Net (loss) income (166,834 ) (201,765 ) (368,599 ) 39,532 (127,801 ) (88,269 ) Basic net (loss) income per share $ (1.04 ) $ (1.26 ) $ (2.30 ) $ 0.27 $ (0.86 ) $ (0.59 ) Diluted net (loss) income per share (1.04 ) (1.26 ) (2.30 ) 0.25 (0.86 ) (0.59 ) The Company’s consolidated statement of comprehensive loss for the year ended December 31, 2016 includes KRYSTEXXA and MIGERGOT net sales as a result of the acquisition of Crealta in January 2016 of $91.1 million and $4.7 million, respectively, and PROCYSBI and QUINSAIR net sales as a result of the acquisition of Raptor in October 2016 of $25.3 million and $1.0 million, respectively. The Company’s consolidated statement of comprehensive income for the year ended December 31, 2015 includes RAVICTI and BUPHENYL net sales as a result of the acquisition of Hyperion in May 2015 of $86.9 million and $13.5 million, respectively. Hyperion, Crealta and Raptor have been integrated into the Company’s business and as a result of these integration efforts, the Company cannot distinguish between these operations and those of the Company’s legacy business.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	NOTE 5 – INVENTORIES Inventories are stated at the lower of cost or market value. Inventories consist of raw materials, work-in-process and finished goods. The Company has entered into manufacturing and supply agreements for the manufacture of finished goods or the purchase of raw materials and production supplies. The Company’s inventories include the direct purchase cost of materials and supplies and manufacturing overhead costs. The components of inventories as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Raw materials $ 4,553 $ 10,233 Work-in-process 27,589 85,022 Finished goods 29,513 79,533 Inventories, net $ 61,655 $ 174,788 Finished goods at December 31, 2017 included $17.0 million of stepped-up KRYSTEXXA inventory. The Company recorded $78.3 million of KRYSTEXXA inventory step-up expense during the year ended December 31, 2017. Finished goods at December 31, 2016 included $27.7 million of stepped-up KRYSTEXXA inventory. Work-in-process at December 31, 2016 included $67.6 million of stepped-up KRYSTEXXA inventory. The Company expects that the KRYSTEXXA inventory step-up will be fully expensed by the end of the first quarter of 2018. Following that period, the Company expects the costs of goods sold related to KRYSTEXXA to decrease significantly to levels consistent with the historical cost of goods sold of Crealta. During the year ended December 31, 2017, the Company recorded $40.8 million of PROCYSBI and QUINSAIR inventory step-up expense. In addition, during the year ended December 31, 2017, the Company recorded $3.2 million of inventory step-up expense to “gain on divestiture” relating to PROCYSBI and QUINSAIR in connection with the Chiesi divestiture in June 2017. Finished goods at December 31, 2016 included $38.1 million of stepped-up PROCYSBI and QUINSAIR inventory. Work-in-process at December 31, 2016 included $5.9 million of stepped-up PROCYSBI and QUINSAIR inventory. Because inventory step-up expense is acquisition-related, will not continue indefinitely and has a significant effect on the Company’s gross profit, gross margin percentage and net income (loss) for all affected periods, the Company discloses balance sheet and income statement amounts related to inventory step-up.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	NOTE 6 – PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Medicine samples inventory $ 11,415 $ 10,192 Rabbi trust assets 6,490 3,073 Other prepaid expenses and other current assets 25,497 36,354 Prepaid expenses and other current assets $ 43,402 $ 49,619

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	NOTE 7 – PROPERTY AND EQUIPMENT Property and equipment as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Software $ 14,956 $ 10,876 Leasehold improvements 9,415 9,184 Machinery and equipment 4,819 4,566 Computer equipment 2,235 3,069 Other 2,508 2,664 33,933 30,359 Less accumulated depreciation (13,672 ) (8,319 ) Construction in process 144 1,444 Property and equipment, net $ 20,405 $ 23,484 The Company capitalizes development costs associated with internal use software, including external direct costs of materials and services and payroll costs for employees devoting time to a software project. Costs incurred during the preliminary project stage, as well as costs for maintenance and training, are expensed as incurred. Depreciation expense for the years ended December 31, 2017, 2016 and 2015 was $6.6 million, $5.0 million and $5.4 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	NOTE 8 – GOODWILL AND INTANGIBLE ASSETS Goodwill The gross carrying amount of goodwill as of December 31, 2017 was as follows (in thousands): Balance at December 31, 2015 $ 253,811 Goodwill recognized on acquisition of Crealta 9,913 Goodwill recognized on acquisition of Raptor 189,046 Adjustment relating to the acquisition of Hyperion in the prior year (7,191 ) Balance at December 31, 2016 445,579 Goodwill derecognized on Chiesi divestiture (16,285 ) Adjustment relating to the acquisition of Raptor in the prior year (2,853 ) Balance at December 31, 2017 $ 426,441 During the year ended December 31, 2017, in connection with the Chiesi divestiture, the Company recorded a reduction to goodwill of $16.3 million. During the year ended December 31, 2016, the Company recognized goodwill with a preliminary value of $189.1 million in connection with the Raptor acquisition, which represented the excess of the purchase price over the fair value of the net assets acquired. During the year ended December 31, 2017, the Company recorded measurement period adjustments related to deferred tax liabilities, accrued trade discounts and rebates and accrued expenses, which resulted in a net decrease in goodwill of $2.9 million, to $186.2 million. During the year ended December 31, 2016, the Company recognized goodwill with a value of $9.9 million in connection with the Crealta acquisition, which represented the excess of the purchase price over the fair value of the net assets acquired. During the year ended December 31, 2016, the Company recorded an adjustment related to deferred tax liabilities which resulted in a decrease to goodwill he adjustment was the result of a correction of an error in the Hyperion pre-acquisition deferred tax calculation. The Company concluded that this misstatement was not material, individually or in the aggregate, to any of the reporting periods impacted. As such, the correction for this error was made during the year ended December 31, 2016. As of December 31, 2017, there were no accumulated goodwill impairment losses. See Note 4 for further details of goodwill acquired and disposed of in business acquisitions and divestitures. Intangible Assets As of December 31, 2017, the Company’s intangible assets consisted of developed technology related to ACTIMMUNE, BUPHENYL, KRYSTEXXA, MIGERGOT, PENNSAID 2%, PROCYSBI, RAVICTI, RAYOS and VIMOVO in the United States, and AMMONAPS, BUPHENYL, LODOTRA and PROCYSBI outside the United States, as well as customer relationships for ACTIMMUNE. During the year ended December 31, 2017, in connection with the Chiesi divestiture, the Company recorded a reduction in the net book value of developed technology related to PROCYSBI of $47.3 million. During the year ended December 31, 2016, in connection with the acquisition of Raptor, the Company capitalized $946.0 million of developed technology related to PROCYSBI. During the year ended December 31, 2016, in connection with the acquisition of Crealta, the Company capitalized $402.2 million of developed technology related to KRYSTEXXA and $26.0 million of developed technology related to MIGERGOT. See Note 4 for further details of intangible assets acquired and disposed of in business acquisitions and divestitures. Prior to the fourth quarter of 2016, the Company had IPR&D of $66.0 million related to one research and development project to evaluate ACTIMMUNE in the treatment of FA. During December 2016, the Company discontinued this project and recorded an impairment charge of $66.0 million to “impairment of in-process research and development” in its consolidated statements of comprehensive loss during the year ended December 31, 2016, to fully write off the value of the asset on its consolidated balance sheet. The Company tests its intangible assets for impairment when events or circumstances may indicate that the carrying value of these assets exceeds their fair value. The Company does not believe there have been any circumstances or events that would indicate that the carrying value of any of its intangible assets, except for IPR&D as described above, was impaired at December 31, 2017 or 2016. As of December 31, 2017 and 2016, amortizable intangible assets consisted of the following (in thousands): As of December 31, 2017 2016 Cost Basis Accumulated Amortization Net Book Value Cost Basis Accumulated Amortization Net Book Value Developed technology $ 3,115,695 $ (671,746 ) $ 2,443,949 $ 3,166,695 $ (399,511 ) $ 2,767,184 Customer relationships 8,100 (2,659 ) 5,441 8,100 (1,849 ) 6,251 Amortizable intangible assets $ 3,123,795 $ (674,405 ) $ 2,449,390 $ 3,174,795 $ (401,360 ) $ 2,773,435 Amortization expense for the years ended December 31, 2017, 2016 and 2015 was $276.8 million, $216.9 million and $132.9 million, respectively. As of December 31, 2017, estimated future amortization expense was as follows (in thousands): 2018 $ 274,084 2019 261,092 2020 261,068 2021 253,373 2022 251,551 Thereafter 1,148,222 Total $ 2,449,390

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Other Assets	NOTE 9 - OTHER ASSETS Included in other assets at December 31, 2017, is $24.6 million which represents the long-term portion of the estimated amounts that are expected to be reimbursed from Chiesi for PROCYSBI and QUINSAIR royalties.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Accrued Expenses [Member]
Accrued Liabilities / Expenses	NOTE 10 – ACCRUED EXPENSES Accrued expenses as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Payroll-related expenses $ 56,338 $ 66,417 Consulting and professional services 27,542 33,614 Accrued interest 14,127 18,938 Accrued upfront payment related to license agreement 12,000 — Litigation settlement — 32,500 Accrued other 27,827 31,296 Accrued expenses $ 137,834 $ 182,765 Accrued litigation settlement at December 31, 2016 included $32.5 million in relation to a litigation settlement with Express Scripts, Inc., which was paid in two equal installments in January 2017 and April 2017. During the year ended December 31, 2017, the Company entered into an agreement to license HZN-003 from MedImmune. Under the terms of the agreement, the Company agreed to pay MedImmune an upfront cash payment of $12.0 million, which was recorded as “research and development” expenses in the consolidated statement of comprehensive loss during the year ended December 31, 2017 and was included in “accrued expenses” as of December 31, 2017. Accrued other as of December 31, 2017 and 2016 included $2.1 million and $9.5 million, respectively, related to a loss on inventory purchase commitments. During the year ended December 31, 2016, the Company committed to purchase additional units of ACTIMMUNE from Boehringer Ingelheim RCV GmbH & Co KG (“Boehringer Ingelheim”). These additional units of ACTIMMUNE were intended to cover anticipated demand if the Phase 3 trial, Safety, Tolerability and Efficacy of ACTIMMUNE Dose Escalation in Friedreich’s Ataxia study (the “FA program”) had been successful. Following the discontinuation of the FA program during the year ended December 31, 2016, the Company recorded a loss of $14.3 million in “cost of goods sold” in the consolidated statement of comprehensive loss for firm, non-cancellable and unconditional purchase commitments for quantities in excess of the Company’s current forecasts for future demand. During the year ended December 31, 2017, the Company renegotiated its purchase commitments with Boehringer Ingelheim and reassessed its excess commitments based on updated forecasts for future demand and recorded additional expense of $1.7 million to “cost of goods sold”. “Other long-term liabilities” as of December 31, 2017 and 2016 included $7.8 million and $4.8 million, respectively, related to this loss on inventory purchase commitments. During the year ended December 31, 2016, the Company recorded $4.0 million related to costs to be incurred to discontinue the clinical trial. Accrued other as of December 31, 2016 included $4.0 million related to these costs. During the year ended December 31, 2017, the Company recorded a reduction of $1.5 million to “research and development” expenses reflecting lower costs to discontinue the clinical trial than previously estimated.

Accrued Trade Discounts and Reb

Accrued Trade Discounts and Rebates	12 Months Ended
	Dec. 31, 2017
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Accrued Liabilities / Expenses	NOTE 11 – ACCRUED TRADE DISCOUNTS AND REBATES Accrued trade discounts and rebates as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Accrued wholesaler fees and commercial rebates $ 190,215 $ 47,460 Accrued co-pay and other patient assistance 230,533 188,504 Accrued government rebates and chargebacks 81,005 61,592 Accrued trade discounts and rebates $ 501,753 $ 297,556 Invoiced wholesaler fees and commercial rebates, co-pay and other patient assistance, and government rebates and chargebacks in accounts payable 15,042 16,830 Total customer-related accruals and allowances $ 516,795 $ 314,386 The following table summarizes changes in the Company’s customer-related accruals and allowances during the years ended December 31, 2017 and 2016 (in thousands): Wholesaler Fees Co-Pay and Government and Commercial Other Patient Rebates and Rebates Assistance Chargebacks Total Balance at December 31, 2015 $ 21,112 $ 114,201 $ 48,456 $ 183,769 Current provisions relating to sales during the year ended December 31, 2016 133,012 1,701,287 278,877 2,113,176 Adjustments relating to prior-year sales 671 — (6,875 ) (6,204 ) Payments relating to sales during the year ended December 31, 2016 (87,147 ) (1,496,240 ) (224,343 ) (1,807,730 ) Payments relating to prior-year sales (20,644 ) (114,201 ) (41,581 ) (176,426 ) Crealta acquisition on January 13, 2016 492 — 932 1,424 Raptor acquisition on October 25, 2016 155 96 6,126 6,377 Balance at December 31, 2016 $ 47,651 $ 205,143 $ 61,592 $ 314,386 Measurement period adjustment — — (1,350 ) (1,350 ) Current provisions relating to sales during the year ended December 31, 2017 635,919 1,907,669 331,559 2,875,147 Adjustments relating to prior-year sales 5,580 (59 ) (4,905 ) 616 Payments relating to sales during the year ended December 31, 2017 (445,621 ) (1,675,344 ) (237,574 ) (2,358,539 ) Payments relating to prior-year sales (53,044 ) (205,084 ) (55,337 ) (313,465 ) Balance at December 31, 2017 $ 190,485 $ 232,325 $ 93,985 $ 516,795

Accrued Royalties

Accrued Royalties	12 Months Ended
	Dec. 31, 2017
Accrued Royalties [Member]
Payables And Accruals [Line Items]
Accrued Liabilities / Expenses	NOTE 12 – ACCRUED ROYALTIES Changes to the liability for royalties for medicines acquired through business combinations during the years ended December 31, 2017 and 2016 consisted of the following (in thousands): Balance as of December 31, 2015 $ 175,219 Accrued royalties - current portion as of December 31, 2015 51,700 Accrued royalties, net of current as of December 31, 2015 123,519 Assumed KRYSTEXXA and MIGERGOT contingent royalty liabilities 51,300 Assumed KRYSTEXXA and MIGERGOT accrued royalties 1,401 Assumed PROCYSBI contingent royalty liabilities 102,000 Assumed PROCYSBI and QUINSAIR accrued royalties 2,705 Remeasurement of royalty liabilities 386 Royalty payments (39,448 ) Accretion expense 40,616 Other royalty expense 95 Balance as of December 31, 2016 334,274 Accrued royalties - current portion as of December 31, 2016 61,981 Accrued royalties, net of current as of December 31, 2016 272,293 Reclassification to other long-term liabilities (5,233 ) Remeasurement of royalty liabilities 21,774 Royalty payments (45,739 ) Accretion expense 51,127 Other royalty expense 310 Balance as of December 31, 2017 356,513 Accrued royalties - current portion as of December 31, 2017 65,328 Accrued royalties, net of current as of December 31, 2017 $ 291,185 The reclassification to other long-term liabilities in the table above relates to the reclassification of a contingent royalty liability for PROCYSBI to other long-term liabilities as a result of the Chiesi divestiture. During the year ended December 31, 2017, based on higher sales of certain of the Company’s medicines versus its previous expectations and estimates for future sales of these medicines, the Company recorded total charges of $64.7 million and $0.6 million to “cost of goods sold” and “selling, general and administrative” expenses, respectively, (primarily composed of $40.5 million and $24.2 million related to KRYSTEXXA and RAVICTI, respectively). The Company also recorded a reduction of $43.5 million to cost of goods sold related to certain of its other medicines as a result of updated estimates of future sales of these medicines (primarily composed of $23.2 million, $11.7 million and $7.0 million related to PROCYSBI, VIMOVO and ACTIMMUNE, respectively).

Long-Term Investments

Long-Term Investments	12 Months Ended
	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Long-Term Investments	NOTE 13 – LONG-TERM INVESTMENTS During the third quarter of 2015, the Company purchased 2,250,000 shares of common stock of Depomed, Inc. (“Depomed”), representing 3.75% of Depomed’s then outstanding common stock. The shares were acquired at a cost of $71.8 million. During the fourth quarter of 2015, following the Company’s decision to withdraw its offer to acquire Depomed, the Company sold all of its shares in Depomed, receiving sales proceeds of $42.8 million and the Company recognized a realized loss of $29.0 million in the consolidated statement of . There were no gains or losses on long-term investments during the years ended December 31, 2017 or 2016.

Segment and Other Information

Segment and Other Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment and Other Information	NOTE 14 – SEGMENT AND OTHER INFORMATION The Company has determined that it operates in one researching, developing and commercializing innovative medicines that address unmet treatment needs The following table presents a summary of total net sales by medicine (in thousands): Year Ended December 31, 2017 2016 2015 RAVICTI $ 193,918 $ 151,532 $ 86,875 PENNSAID 2% 191,050 304,433 147,010 KRYSTEXXA 156,483 91,102 — PROCYSBI 137,740 25,268 — DUEXIS 121,161 173,728 190,357 ACTIMMUNE 110,993 104,624 107,444 VIMOVO 57,666 121,315 166,672 RAYOS 52,125 47,356 40,329 BUPHENYL 20,792 16,879 13,458 MIGERGOT 5,468 4,651 — LODOTRA 5,393 4,193 4,899 QUINSAIR 3,442 1,039 — Litigation settlement — (65,000 ) — Total net sales $ 1,056,231 $ 981,120 $ 757,044 The following table presents a summary of total net sales by geography (in thousands, except for percentages): Year Ended December 31, Year Ended December 31, 2016 Year Ended December 31, 2015 Amount % of Total Net Sales Amount % of Total Net Sales Amount % of Total Net Sales United States $ 1,026,527 97% $ 964,041 98% $ 744,036 98% Rest of world 29,704 3% 17,079 2% 13,008 2% Total net sales $ 1,056,231 $ 981,120 $ 757,044 The following table presents the amount and percentage of gross sales from customers that represented more than 10% of the Company’s gross sales included in its single operating segment, and all other customers as a group (in thousands, except percentages): Year ended December 31, 2017 2016 2015 Amount % of Gross Sales Amount % of Gross Sales Amount % of Gross Sales Customer A $ 1,205,268 30% $ 1,413,774 44% $ 607,771 30% Customer B 1,165,591 29% 667,031 21% 166,661 8% Customer C 567,583 14% 355,920 11% 207,009 10% Other Customers 1,119,397 27% 797,463 24% 1,075,853 52% Gross Sales $ 4,057,839 100% $ 3,234,188 100% $ 2,057,294 100% The following table presents total tangible long-lived assets by location (in thousands): As of December 31, 2017 2016 United States $ 17,089 $ 19,542 Other 3,316 3,942 Total long-lived assets (1) $ 20,405 $ 23,484 (1) Long-lived assets consist of property and equipment.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 15 – FAIR VALUE MEASUREMENTS The following tables and paragraphs set forth the Company’s financial instruments that are measured at fair value on a recurring basis within the fair value hierarchy. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The following describes three levels of inputs that may be used to measure fair value: Level 1 —Observable inputs such as quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company utilizes the market approach to measure fair value for its money market funds. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. As of December 31, 2017, the Company’s restricted cash included bank time deposits which were measured at fair value using Level 2 inputs and their carrying values were approximately equal to their fair values. Level 2 inputs, obtained from various third-party data providers, represent quoted prices for similar assets in active markets, or these inputs were derived from observable market data, or if not directly observable, were derived from or corroborated by other observable market data. Other current assets and other long-term liabilities recorded at fair value on a recurring basis are composed of investments held in a rabbi trust and the related deferred liability for deferred compensation arrangements. Quoted prices for this investment, primarily in mutual funds, are available in active markets. Thus, the Company’s investments related to deferred compensation arrangements and the related long-term liability are classified as Level 1 measurements in the fair value hierarchy. The Company transfers its financial assets and liabilities between fair value hierarchies at the end of each reporting period. There were no transfers between the different levels of the fair value hierarchy in 2017 or in 2016. Assets and liabilities measured at fair value on a recurring basis The following table sets forth the Company’s financial assets and liabilities at fair value on a recurring basis as of December 31, 2017 and 2016 (in thousands): December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Bank time deposits $ — $ 3,000 $ — $ 3,000 Money market funds 687,000 — — 687,000 Other current assets 6,490 — — 6,490 Total assets at fair value $ 693,490 $ 3,000 $ — $ 696,490 Liabilities: Other long-term liabilities (6,490 ) — — (6,490 ) Total liabilities at fair value $ (6,490 ) $ — $ — $ (6,490 ) December 31, 2016 Level 1 Level 2 Level 3 Total Assets: Bank time deposits $ — $ 3,000 $ — $ 3,000 Money market funds 170,000 — — 170,000 Other current assets 3,038 — — 3,038 Total assets at fair value $ 173,038 $ 3,000 $ — $ 176,038 Liabilities: Other long-term liabilities (3,038 ) — — (3,038 ) Total liabilities at fair value $ (3,038 ) $ — $ — $ (3,038 )

Debt Agreements

Debt Agreements	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt Agreements	NOTE 16 – DEBT AGREEMENTS The Company’s outstanding debt balances as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 2017 Term Loan Facility $ 845,750 $ — 2015 Term Loan Facility — 394,000 2016 Incremental Loan Facility — 375,000 2023 Senior Notes 475,000 475,000 2024 Senior Notes 300,000 300,000 Exchangeable Senior Notes 400,000 400,000 Total face value 2,020,750 1,944,000 Debt discount (108,054 ) (126,352 ) Deferred financing fees (11,041 ) (10,155 ) Total long-term debt 1,901,655 1,807,493 Less: current maturities 10,625 7,750 Long-term debt, net of current maturities $ 1,891,030 $ 1,799,743 Scheduled maturities with respect to the Company’s long-term debt are as follows (in thousands): 2018 $ 10,625 2019 8,500 2020 8,500 2021 8,500 2022 406,375 Thereafter 1,578,250 Total $ 2,020,750 2017 Term Loan Facilities On October 23, 2017, HPI and Horizon Pharma USA, Inc. (“HPUSA” and, together with HPI, in such capacity, the “Borrowers”), wholly owned subsidiaries of the Company, borrowed approximately $845.8 million aggregate principal amount of loans (the “October 2017 Refinancing Loans”) pursuant to an amendment (the “October 2017 Refinancing Amendment”) to the credit agreement, dated as of May 7, 2015, by and among the Borrowers, the Company and certain of its subsidiaries as guarantors, the lenders party thereto from time to time and Citibank, N.A., as administrative agent and collateral agent, as amended by Amendment No. 1, dated as of October 25, 2016 (the “2016 Credit Agreement”), and Amendment No. 2, dated March 29, 2017 (the “March 2017 Credit Agreement”) (the “2017 Term Loan Facility”). As used herein, all references to the “Credit Agreement” are references to the March 2017 Credit Agreement, as amended by the October 2017 Refinancing Amendment. The October 2017 Refinancing Loans were incurred as a separate new class of term loans under the Credit Agreement with substantially the same terms as the previously outstanding senior secured term loans incurred on March 29, 2017 under the March 2017 Credit Agreement (the “October 2017 Refinanced Loans”) to effectuate a repricing of the October 2017 Refinanced Loans. The Borrowers used the proceeds of the October 2017 Refinancing Loans to repay the October 2017 Refinanced Loans, which totaled approximately $845.8 million. The October 2017 Refinancing Loans bear interest, at the Borrowers’ option, at a rate equal to either the London Inter-Bank Offer Rate (“LIBOR”), plus an applicable margin of 3.25% per year (subject to a LIBOR floor of 1.00%), or the adjusted base rate plus 2.25%. The adjusted base rate is defined as the greater of (a) LIBOR (using one-month interest period) plus 1.00%, (b) prime rate, (c) fed funds plus 0.5%, and (d) 2.00%. The Credit Agreement provides for (i) the October 2017 Refinancing Loans, (ii) one or more uncommitted additional incremental loan facilities subject to the satisfaction of certain financial and other conditions, and (iii) one or more uncommitted refinancing loan facilities with respect to loans thereunder. The Credit Agreement allows for the Company and certain of its subsidiaries to become borrowers under incremental or refinancing facilities. The Company elected to exercise its reinvestment rights under the mandatory prepayment provisions of the March 2017 Credit Agreement with respect to the net proceeds from the Chiesi divestiture. To the extent the Company does not apply such net proceeds to permitted acquisitions (including the acquisition of rights to products and products lines) and/or the acquisition of capital assets within 365 days of the receipt thereof (or commit to so apply and then apply within 180 days after the end of such 365-day period), the Borrowers under the March 2017 Credit Agreement would be required to make a mandatory prepayment under the March 2017 Credit Agreement in an amount equal to the unapplied net proceeds. Until such time, the net proceeds are not legally restricted for use. As of December 31, 2017, the Company had applied a portion of such net proceeds to the acquisition of additional rights to interferon gamma-1b and to the agreement to license HZN-003. See Note 4 for further details of this acquisition and license agreement. The obligations under the Credit Agreement (including obligations in respect of the October 2017 Refinancing Loans) and any swap obligations and cash management obligations owing to a lender (or an affiliate of a lender) thereunder are guaranteed by the Company and each of the Company’s existing and subsequently acquired or formed direct and indirect subsidiaries (other than certain immaterial subsidiaries, subsidiaries whose guarantee would result in material adverse tax consequences and subsidiaries whose guarantee is prohibited by applicable law). The obligations under the Credit Agreement (including obligations in respect of the October 2017 Refinancing Loans) and any such swap and cash management obligations are secured, subject to customary permitted liens and other agreed upon exceptions, by a perfected security interest in (i) all tangible and intangible assets of the Borrowers and the guarantors, except for certain customary excluded assets, and (ii) all of the capital stock owned by the Borrowers and guarantors thereunder (limited, in the case of the stock of certain non-U.S. subsidiaries of the Borrowers, to 65% of the capital stock of such subsidiaries). The Borrowers and the guarantors under the Credit Agreement are individually and collectively referred to herein as a “Loan Party” and the “Loan Parties,” as applicable. Borrowers under the Credit Agreement are permitted to make voluntary prepayments of the loans under the Credit Agreement at any time without payment of a premium, except that with respect to the October 2017 Refinancing Loans, a 1.00% premium will apply to a repayment of the October 2017 Refinancing Loans in connection with a repricing of, or any amendment to the Credit Agreement in a repricing of, such loans effected on or prior to the date that is six months following October 23, 2017. The Borrowers are required to make mandatory prepayments of loans under the Credit Agreement (without payment of a premium) with (a) net cash proceeds from certain non-ordinary course asset sales (subject to reinvestment rights and other exceptions), (b) casualty proceeds and condemnation awards (subject to reinvestment rights and other exceptions), (c) net cash proceeds from issuances of debt (other than certain permitted debt), and (d) 50% of the Company’s excess cash flow (subject to decrease to 25% or 0% if the Company’s first lien leverage ratio is less than 2.25:1 or 1.75:1, respectively). The October 2017 Refinancing Loans will amortize in equal quarterly installments beginning on December 31, 2017, in an aggregate annual amount equal to 1.00% of the original principal amount of the October 2017 Refinanced Loans (i.e. $850.0 million), with any remaining balance payable on March 29, 2024, the final maturity date of the October 2017 Refinancing Loans. The Credit Agreement contains customary representations and warranties and customary affirmative and negative covenants, including, among other things, restrictions on indebtedness, liens, investments, mergers, dispositions, prepayment of other indebtedness and dividends and other distributions. Events of default under the Credit Agreement include: (i) the failure by any Borrower to timely make payments due under the Credit Agreement; (ii) material misrepresentations or misstatements in any representation or warranty by any Loan Party when made; (iii) failure by any Loan Party to comply with the covenants under the Credit Agreement and other related agreements; (iv) certain defaults under a specified amount of other indebtedness of the Company or its subsidiaries; (v) insolvency or bankruptcy-related events with respect to the Company or any of its material subsidiaries; (vi) certain undischarged judgments against the Company or any of its restricted subsidiaries; (vii) certain ERISA-related events reasonably expected to have a material adverse effect on the Company and its restricted subsidiaries taken as a whole; (viii) certain security interests or liens under the loan documents ceasing to be, or being asserted by the Company or its restricted subsidiaries not to be, in full force and effect; (ix) any loan document or material provision thereof ceasing to be, or any challenge or assertion by any Loan Party that such loan document or material provision is not, in full force and effect; and (x) the occurrence of a change of control. If one or more events of default occurs and continues beyond any applicable cure period, the administrative agent may, with the consent of the lenders holding a majority of the loans and commitments under the facilities, or will, at the request of such lenders, terminate the commitments of the lenders to make further loans and declare all of the obligations of the Loan Parties under the March 2017 Credit Agreement to be immediately due and payable. The interest on the Company’s 2017 Term Loan Facility is variable and as of December 31, 2017, the interest rate on the 2017 Term Loan Facility was 4.75% and the effective interest rate was 5.16%. As of December 31, 2017, the fair value of the amounts outstanding under the 2017 Term Loan Facility was approximately $848.9 million, categorized as a Level 2 instrument, as defined in Note 15. 2016 Incremental Loan Facility and 2015 Term Loan Facility On May 7, 2015, HPI, as borrower, and the Company and certain of its subsidiaries, as guarantors, entered into a credit agreement (the “2015 Credit Agreement”) with Citibank, N.A., as administrative and collateral agent, and the lenders from time to time party thereto providing for (i) a six-year $400.0 million term loan facility (the Loans”) under the 2015 Term Loan Facility bore interest, at each borrower’s option, at a rate equal to either the LIBOR, plus HPI borrowed the full $400.0 million available on the 2015 Term Loan Facility on May 7, 2015 as a LIBOR-based borrowing. On October 25, 2016 and in connection with the financing for the acquisition of Raptor, HPI and HPUSA (together, in such capacity, the “Incremental Borrowers”) entered into an amendment to the 2015 Credit Agreement (the “2016 Amendment”) with Citibank, N.A., as administrative and collateral agent, and Bank of America, N.A., as the incremental B-1 lender thereunder, pursuant to which the Incremental Borrowers borrowed $375.0 million aggregate principal amount of loans (the “2016 Incremental Loan Facility”). The 2016 Incremental Loan Facility was incurred as a separate class of term loans under the 2015 Credit Agreement with the same terms as the loans under the 2015 Term Loan Facility, except as described below. The senior secured term loans (the “2016 Loans”) under the 2016 Incremental Loan Facility bore interest, at the Incremental Borrowers’ option, at a rate equal to either LIBOR plus an applicable margin of 4.50% per year (subject to a LIBOR floor of 1.00%), or the adjusted base rate plus 3.50%. The terms of the 2015 Loans provided for an amendment such that the effective yield of the 2015 Loans would not be less than the effective yield of the 2016 Loans minus 0.50%. Consequently, the issuance of the 2016 Loans resulted in an increase of the interest rate applicable to the 2015 Loans, as of October 25, 2016, to LIBOR plus 4.00%, subject to a LIBOR floor of 1.00% (an initial interest rate of 5.00%). On March 29, 2017, the The 2015 Loans and the 2016 Loans were repaid, and a portion of the repayment was accounted for as a debt modification and a portion was accounted for as a debt extinguishment. Under debt extinguishment accounting, the Company recorded a charge of $0.5 million to “loss on debt extinguishment” in the consolidated statements of comprehensive loss, which reflected the write-off of the unamortized portion of debt discount and deferred financing costs previously incurred and a one percent prepayment penalty fee. Under debt modification accounting, the Company capitalized an incremental $5.8 million of debt discount and deferred financing fees. 2023 Senior Notes On April 29, 2015, Horizon Pharma Financing Inc. (“Horizon Financing”), a wholly owned subsidiary of the Company, completed a private placement of $475.0 million aggregate principal amount of 6.625% Senior Notes due 2023 (the “2023 Senior Notes”) to certain investment banks acting as initial purchasers who subsequently resold the 2023 Senior Notes to qualified institutional buyers as defined in Rule 144A under the Securities Act, and in offshore transactions to non-U.S. persons in reliance on Regulation S under the Securities Act. The net proceeds from the offering of the 2023 Senior Notes were approximately $462.3 million, after deducting the initial purchasers’ discount and offering expenses payable by Horizon Financing. In connection with the closing of the Hyperion acquisition on May 7, 2015, Horizon Financing merged with and into HPI and, as a result, the 2023 Senior Notes became HPI’s general unsecured senior obligations. The obligations under the 2023 Senior Notes are fully and unconditionally guaranteed on a senior unsecured basis by the Company and all of the Company’s direct and indirect subsidiaries that are guarantors from time to time under the Credit Agreement. The 2023 Senior Notes accrue interest at an annual rate of 6.625% payable semiannually in arrears on May 1 and November 1 of each year, beginning on November 1, 2015. The 2023 Senior Notes will mature on May 1, 2023, unless earlier repurchased or redeemed. Except as described below, the 2023 Senior Notes may not be redeemed before May 1, 2018. Thereafter, some or all of the 2023 Senior Notes may be redeemed at any time at specified redemption prices, plus accrued and unpaid interest to the redemption date. At any time prior to May 1, 2018, some or all of the 2023 Senior Notes may be redeemed at a price equal to 100% of the aggregate principal amount thereof, plus a make-whole premium and accrued and unpaid interest to the redemption date. Also prior to May 1, 2018, up to 35% of the aggregate principal amount of the 2023 Senior Notes may be redeemed at a redemption price of 106.625% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings. In addition, the 2023 Senior Notes may be redeemed in whole but not in part at a redemption price equal to 100% of the principal amount plus accrued and unpaid interest and additional amounts, if any, to, but excluding, the redemption date, if on the next date on which any amount would be payable in respect of the 2023 Senior Notes, HPI or any guarantor is or would be required to pay additional amounts as a result of certain tax-related events. If the Company undergoes a change of control, HPI will be required to make an offer to purchase all of the 2023 Senior Notes at a price in cash equal to 101% of the aggregate principal amount thereof plus accrued and unpaid interest to, but not including, the repurchase date. If the Company or certain of its subsidiaries engages in certain asset sales, HPI will be required under certain circumstances to make an offer to purchase the 2023 Senior Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the repurchase date. The indenture governing the 2023 Senior Notes contains covenants that limit the ability of the Company and its restricted subsidiaries to, among other things, pay dividends or distributions, repurchase equity, prepay junior debt and make certain investments, incur additional debt and issue certain preferred stock, incur liens on assets, engage in certain asset sales, merge, consolidate with or merge or sell all or substantially all of their assets, enter into transactions with affiliates, designate subsidiaries as unrestricted subsidiaries, and allow to exist certain restrictions on the ability of restricted subsidiaries to pay dividends or make other payments to the Company. Certain of the covenants will be suspended during any period in which the notes receive investment grade ratings. The indenture governing the 2023 Senior Notes As of December 31, 2017, the interest rate on the 2023 Senior Notes was 6.63% and the effective interest rate 6.68%. As of December 31, 2017, the fair value of the 2023 Senior Notes was approximately $473.8 million, categorized as a Level 2 instrument, as defined in Note 15. 2024 Senior Notes On October 25, 2016, HPI and HPUSA (together, in such capacity, the “2024 Issuers”) The net proceeds from the offering of the 2024 Senior Notes were approximately $291.9 million, after deducting the initial purchasers’ discount and offering expenses payable by the 2024 Issuers. The obligations under the 2024 Senior Notes are the 2024 Issuers’ general unsecured senior obligations and are fully and unconditionally guaranteed on a senior unsecured basis by the Company and all of the Company’s direct and indirect subsidiaries that are guarantors from time to time under the Credit Agreement. The Company used the net proceeds from the offering of the 2024 Senior Notes as well as $375.0 million principal amount of 2016 Loans under the to fund a portion of the acquisition of Raptor, repay Raptor’s outstanding debt, and pay any prepayment premiums, fees and expenses in connection with the foregoing. The 2024 Senior Notes accrue interest at an annual rate of 8.750% payable semiannually in arrears on May 1 and November 1 of each year, beginning on May 1, 2017. The 2024 Senior Notes will mature on November 1, 2024, unless earlier repurchased or redeemed. Except as described below, the 2024 Senior Notes may not be redeemed before November 1, 2019. Thereafter, some or all of the 2024 Senior Notes may be redeemed at any time at specified redemption prices, plus accrued and unpaid interest to the redemption date. At any time prior to November 1, 2019, some or all of the 2024 Senior Notes may be redeemed at a price equal to 100% of the aggregate principal amount thereof, plus a make-whole premium and accrued and unpaid interest to the redemption date. Also prior to November 1, 2019, up to 35% of the aggregate principal amount of the 2024 Senior Notes may be redeemed at a redemption price of 108.75% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings. In addition, the 2024 Senior Notes may be redeemed in whole but not in part at a redemption price equal to 100% of the principal amount plus accrued and unpaid interest and additional amounts, if any, to, but excluding, the redemption date, if on the next date on which any amount would be payable in respect of the 2024 Senior Notes, the 2024 Issuers or any guarantor is or would be required to pay additional amounts as a result of certain tax-related events. If the Company undergoes a change of control, the 2024 Issuers will be required to make an offer to purchase all of the 2024 Senior Notes at a price in cash equal to 101% of the aggregate principal amount thereof plus accrued and unpaid interest to, but not including, the repurchase date. If the Company or certain of its subsidiaries engages in certain asset sales, the 2024 Issuers will be required under certain circumstances to make an offer to purchase the 2024 Senior Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the repurchase date. The indenture governing the 2024 Senior Notes contains covenants that limit the ability of the Company and its restricted subsidiaries to, among other things, pay dividends or distributions, repurchase equity, prepay junior debt and make certain investments, incur additional debt and issue certain preferred stock, incur liens on assets, engage in certain asset sales, merge, consolidate with or merge or sell all or substantially all of their assets, enter into transactions with affiliates, designate subsidiaries as unrestricted subsidiaries, and allow to exist certain restrictions on the ability of restricted subsidiaries to pay dividends or make other payments to the Company. Certain of the covenants will be suspended during any period in which the notes receive investment grade ratings. The indenture also includes customary events of default. As of December 31, 2017, the interest rate on the 2024 Senior Notes was 8.75% and the effective interest rate 9.20%. As of December 31, 2017, the fair value of the 2024 Senior Notes was approximately $316.5 million, categorized as a Level 2 instrument, as defined in Note 15. Exchangeable Senior Notes On March 13, 2015, Horizon Investment completed a private placement of $400.0 million aggregate principal amount of Exchangeable Senior Notes to certain investment banks acting as initial purchasers who subsequently resold the Exchangeable Senior Notes to qualified institutional buyers as defined in Rule 144A under the Securities Act. The net proceeds from the offering of the Exchangeable Senior Notes were approximately $387.2 million, after deducting the initial purchasers’ discount and offering expenses payable by Horizon Investment. The Exchangeable Senior Notes are fully and unconditionally guaranteed, on a senior unsecured basis, by the Company (the “Guarantee”). The Exchangeable Senior Notes and the Guarantee are Horizon Investment’s and the Company’s senior unsecured obligations. The Exchangeable Senior Notes accrue interest at an annual rate of 2.50% payable semiannually in arrears on March 15 and September 15 of each year, beginning on September 15, 2015. The Exchangeable Senior Notes will mature on March 15, 2022, unless earlier exchanged, repurchased or redeemed. The initial exchange rate is 34.8979 ordinary shares of the Company per $1,000 principal amount of the Exchangeable Senior Notes (equivalent to an initial exchange price of approximately $28.66 per ordinary share). The exchange rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date or upon a tax redemption, Horizon Investment will increase the exchange rate for a holder who elects to exchange its Exchangeable Senior Notes in connection with such a corporate event or a tax redemption in certain circumstances. Other than as described below, the Exchangeable Senior Notes may not be redeemed by the Company. Issuer Redemptions: Optional Redemption for Changes in the Tax Laws of a Relevant Taxing Jurisdiction Horizon Investment may redeem the Exchangeable Senior Notes at its option, prior to March 15, 2022, in whole but not in part, in connection with certain tax-related events. Provisional Redemption on or After March 20, 2019 On or after March 20, 2019, Horizon Investment may redeem for cash all or a portion of the Exchangeable Senior Notes if the last reported sale price of ordinary shares of the Company has been at least 130% of the exchange price then in effect for at least twenty trading days whether or not consecutive) during any thirty consecutive trading day period ending on, and including, the trading day immediately preceding the date on which Horizon Investment provide written notice of redemption. The redemption price will be equal to 100% of the principal amount of the Exchangeable Senior Notes to be redeemed, plus accrued and unpaid interest to, but not including, the redemption date; provided that if the redemption date occurs after a regular record date and on or prior to the corresponding interest payment date, Horizon Investment will pay the full amount of accrued and unpaid interest due on such interest payment date to the record holder of the Exchangeable Senior Notes on the regular record date corresponding to such interest payment date, and the redemption price payable to the holder who presents an Exchangeable Senior Note for redemption will be equal to 100% of the principal amount of such Exchangeable Senior Note. Holder Exchange Rights: Holders may exchange all or any portion of their Exchangeable Senior Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2021 only upon satisfaction of one or more of the following conditions: 1. Exchange upon Satisfaction of Sale Price Condition 2. Exchange upon Satisfaction of Trading Price Condition 3. Exchange upon Notice of Redemption As of December 31, 2017, none of the above conditions had been satisfied and no exchange of Exchangeable Senior Notes had been triggered. On or after December 15, 2021, a holder may exchange all or any portion of its Exchangeable Senior Notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date regardless of the foregoing conditions. Upon exchange, Horizon Investment will settle exchanges of the Exchangeable Senior Notes by paying or causing to be delivered, as the case may be, cash, ordinary shares or a combination of cash and ordinary shares, at its election. The Company recorded the Exchangeable Senior Notes under the guidance in ASC Topic 470-20, Debt with Conversion and Other Options, As of December 31, 2017, the interest rate on the Exchangeable Senior Notes was 2.50% and the effective interest rate was 8.88%. As of December 31, 2017, the fair value of the Exchangeable Senior Notes was approximately $372.0 million, categorized as a Level 2 instrument, as defined in Note 15.

Other Long-Term Liabilities

Other Long-Term Liabilities	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Other Long-Term Liabilities	NOTE 17 – OTHER LONG-TERM LIABILITIES Included in other long-term liabilities at December 31, 2017 and 2016, is $26.4 million and $25.5 million, respectively, representing the fair value of the long-term portion of the contingent liability for royalties potentially payable under agreements related to PROCYSBI and QUINSAIR. See Note 10 for details of amounts included in other long-term liabilities at December 31, 2017 and 2016, related to a loss on inventory purchase commitments.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 18 – COMMITMENTS AND CONTINGENCIES Lease Obligations The Company has the following office space lease agreements in place for real properties: Location Approximate Square Footage Lease Expiry Date Dublin, Ireland 18,900 November 3, 2029 Lake Forest, Illinois (1) 160,000 March 31, 2024 Novato, California (2) 61,000 August 31, 2021 Deerfield, Illinois (3) 32,300 June 30, 2018 Brisbane, California 20,100 November 30, 2019 Mannheim, Germany 14,300 December 31, 2018 Chicago, Illinois 6,500 December 31, 2018 Other 13,300 March 31, 2018 to May 31, 2020 (1) In connection with the Lake Forest lease, the Company has provided a $2.0 million letter of credit to the landlord, through a commercial bank. (2) During March 2017, the Company vacated an area of the office space in Novato, California. During March and April 2017, the Company entered into sublease arrangements for this space with third parties. (3) During January 2016, the Company vacated the premises in Deerfield, Illinois and began occupying the premises in Lake Forest, Illinois. During April 2017, the Company entered into a sublease arrangement for a portion of this space with a third party. During June 2017, the Company terminated a portion of the lease, resulting in 32,300 square feet remaining. The Company recognizes rent expense on a monthly basis over the lease term based on a straight-line method. Rent expense was $6.4 million, $5.1 million and $2.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, minimum future cash payments due under lease obligations were as follows (in thousands): 2018 $ 7,356 2019 6,659 2020 5,951 2021 5,350 2022 4,092 Thereafter 11,994 Total $ 41,402 Purchase Commitments In November 2010, Raptor and Patheon entered into a manufacturing services agreement, which the Company assumed as a result of its acquisition of Raptor. Under the agreement, which was amended in April 2012 and June 2013, Patheon is obligated to manufacture PROCYSBI for the Company through December 31, 2019. The Company must provide Patheon with rolling, non-binding forecasts of PROCYSBI, with a portion of the forecast being a firm written order. In November 2010, Raptor and Cambrex Profarmaco Milano (“Cambrex”) entered into an active pharmaceutical ingredient (“API”) supply agreement, which the Company assumed as a result of its acquisition of Raptor. Under the agreement, which was amended in April 2013 and August 2016, Cambrex is obligated to manufacture PROCYSBI API for the Company through November 30, 2020. The Company must provide Cambrex with rolling, non-binding forecasts, with a portion of the forecast being the minimum floor of the firm order that must be placed. At December 31, 2017, the Company had a binding purchase commitment with Patheon for PROCYSBI of $1.8 million, which is to be delivered through April 2018 and with Cambrex for PROCYSBI API of $2.4 million, which is to be delivered through December 2020. In July 2013, Vidara Therapeutics International Public Limited Company (“Vidara”) and Boehringer Ingelheim entered into an exclusive supply agreement, which the Company assumed in September 2014 and amended effective as of September 5, 2014, and June 1, 2015. That supply agreement was replaced with an exclusive global supply agreement between the Company and Boehringer Ingelheim Biopharmaceuticals GmbH (“Boehringer Ingelheim Biopharmaceuticals”) effective June 30, 2017. Under the agreement, Boehringer Ingelheim Biopharmaceuticals is required to manufacture and supply ACTIMMUNE and IMUKIN to the Company. The Company is required to purchase minimum quantities of finished medicine during the term of the agreement, which term extends to at least June 30, 2024. During the year ended December 31, 2016, the Company committed to purchase additional amounts of ACTIMMUNE from Boehringer Ingelheim. These additional amounts were intended to cover anticipated demand if the results of the FA program of ACTIMMUNE for the treatment of FA had been successful. As of December 31, 2017, the minimum binding purchase commitment to Boehringer Ingelheim Biopharmaceuticals was $24.3 million (converted using a Dollar-to-Euro exchange rate of 1.2003) through July 2024. Following the discontinuation of the FA program, the Company recorded a loss of $14.3 million in “cost of goods sold” in the consolidated statement of comprehensive loss during the year ended December 31, 2016 for firm, non-cancellable and unconditional purchase commitments for quantities in excess of the Company’s current forecasts for future demand. During the year ended December 31, 2017, the Company renegotiated the purchase commitments with Boehringer Ingelheim and reassessed its excess commitments based on updated forecasts for future demand and recorded an additional net expense of $1.7 million to “cost of goods sold”. During the year ended December 31, 2016, the Company also committed to incur an additional $14.9 million for the harmonization of the drug substance manufacturing process with Boehringer Ingelheim. These additional costs were incurred and will be incurred during the years 2017 through 2021. During the year ended December 31, 2017 In March 2007, Savient Pharmaceuticals, Inc. (as predecessor in interest to Crealta), entered into a commercial supply agreement with Bio-Technology General (Israel) Ltd (“BTG Israel”) for the production of the bulk KRYSTEXXA medicine (“bulk product”). The Company assumed this agreement as part of the Crealta acquisition and amended the agreement in September 2016. Under this agreement, the Company has agreed to purchase certain minimum annual order quantities and is obligated to purchase at least eighty percent of its annual world-wide bulk product requirements from BTG Israel. The term of the agreement runs until December 31, 2030, and will automatically renew for successive three year periods unless earlier terminated by either party upon three years’ prior written notice. The agreement may be terminated earlier by either party in the event of a force majeure, liquidation, dissolution, bankruptcy or insolvency of the other party, uncured material breach by the other party or after January 1, 2024, upon three years’ prior written notice. Under the agreement i f the manufacture of the is moved out of Israel, the Company may be required to obtain the approval of the Israeli Office of the Chief Scientist (“OCS”) because certain KRYSTEXXA intellectual property was initially developed with a grant funded by the OCS. In August 2007, the Company entered into a manufacturing and supply agreement with Jagotec AG (“Jagotec”), which was amended in March 2011 and in January 2017. Under the agreement, Jagotec or its affiliates are required to manufacture and supply RAYOS/LODOTRA exclusively to the Company in bulk. The earliest the agreement can expire is December 31, 2023, and the minimum purchase commitment is in force until December 2023. At December 31, 2017, the minimum purchase commitment based on tablet pricing in effect under the agreement was $6.7 million through December 2023. Additionally, purchase orders relating to the manufacture of RAYOS/LODOTRA of $0.5 million were outstanding at December 31, 2017. In October 2014, in connection with the acquisition of the U.S. rights to PENNSAID 2% from Nuvo Pharmaceuticals Inc. (formerly known as Nuvo Research Inc.) (“Nuvo”), the Company and Nuvo entered into an exclusive supply agreement. Under the supply agreement, which was amended in February 2016, January 2017 and February 2018, Nuvo is obligated to manufacture and supply PENNSAID 2% to the Company. The term of the supply agreement is through December 31, 2029, but the agreement may be terminated earlier by either party for any uncured material breach by the other party of its obligations under the supply agreement or upon the bankruptcy or similar proceeding of the other party. At least ninety days prior to the first day of each calendar month during the term of the supply agreement, the Company submits a binding written purchase order to Nuvo for PENNSAID 2% in minimum batch quantities. At December 31, 2017, the Company had a binding purchase commitment with Nuvo for PENNSAID 2% of $2.7 million, which was delivered through February 2018. In May 2011, the Company entered into a manufacturing and supply agreement with Sanofi-Aventis U.S. LLC (“Sanofi-Aventis U.S.”), and amended the agreement effective as of September 25, 2013. Pursuant to the agreement, as amended, Sanofi-Aventis U.S. is obligated to manufacture and supply DUEXIS to the Company in final, packaged form, and the Company is obligated to purchase DUEXIS exclusively from Sanofi-Aventis U.S. for the commercial requirements of DUEXIS in North America, South America and certain countries and territories in Europe, including the European Union (“EU”) member states and Scandinavia. The agreement term extends until May 2019, and automatically renews for successive two-year terms unless terminated by either party upon two years’ prior written notice. At December 31, 2017, the Company had a binding purchase commitment to Sanofi-Aventis U.S. for DUEXIS of $7.1 million, which is to be delivered through June 2018. Excluding the above, additional purchase orders and other commitments relating to the manufacture of RAVICTI, BUPHENYL, QUINSAIR, VIMOVO and MIGERGOT of $12.4 million were outstanding at December 31, 2017. Additionally, at December 31, 2017, the Company had a binding purchase commitment related to process validation activities for teprotumumab of $2.8 million. Royalty and Milestone Agreements RAVICTI Under the terms of an asset purchase agreement with Ucyclyd Pharma, Inc. (“Ucyclyd”), the Company is obligated to pay to Ucyclyd tiered mid to high single-digit royalties on its global net sales of RAVICTI. Under the terms of a license agreement with aul W. Brusilow, M.D. and Brusilow Enterprises (“Brusilow”), PROCYSBI Under the terms of an amended and restated license agreement with UCSD, the Company is obligated to pay to UCSD tiered low to mid-single-digit royalties on its net sales of PROCYSBI, including a minimum annual royalty in an amount less than $0.1 million. The Company must also pay of any fees it receives from its sublicensees under the agreement that are not earned royalties. The Company may also be obligated to pay UCSD aggregate developmental milestone payments of $0.3 million and aggregate regulatory milestone payments of $1.8 million for each orphan indication, and aggregate developmental milestone payments of $0.8 million and aggregate regulatory milestone payments of $3.5 million for each non-orphan indication. ACTIMMUNE Under a license agreement, as amended, with Genentech Inc. (“Genentech”), who was the original developer of ACTIMMUNE, the Company is, or was, obligated to pay royalties to Genentech on its net sales of ACTIMMUNE as follows: • For the period from November 26, 2014 through May 5, 2018, a royalty in the 20% to 30% range for the first $3.7 million in net sales achieved in any calendar year and in the 1% to 9% range for all additional net sales in any year; and • From May 6, 2018 and for so long as the Company continues to commercially sell ACTIMMUNE, an annual royalty in the low single digits as a percentage of annual net sales. Under the terms of an assignment and option agreement with Connetics Corporation (which was the predecessor parent company to InterMune Pharmaceuticals Inc. and is now part of GlaxoSmithKline), (“Connetics”), the Company is obligated to pay low single-digit royalties to Connetics on the Company’s net sales of ACTIMMUNE in the United States. BUPHENYL Under the terms of an amended and restated collaboration agreement with Ucyclyd, the Company is obligated to pay to Ucyclyd tiered mid to high single-digit royalties on its net sales in the United States of BUPHENYL to urea cycle disorder patients outside of the U.S. Food and Drug Administration (“FDA”) approved labeled age range for RAVICTI. KRYSTEXXA Under the terms of a license agreement with Duke and MVP, the Company is obligated to pay Duke a mid-single-digit royalty on its global net sales of KRYSTEXXA and a royalty of between 5% and 15% on any global sublicense revenue. The Company is also obligated to pay MVP a mid-single-digit royalty on its net sales of KRYSTEXXA outside of the United States and a royalty of between 5% and 15% on any sublicense revenue outside of the United States. RAYOS/LODOTRA Jagotec is entitled to receive a mid-single digit percentage royalty on adjusted gross sales of RAYOS/LODOTRA and on any sub-licensing income, which includes any payments not calculated based on the adjusted gross sales of RAYOS/LODOTRA, such as license fees, lump sums and milestone payments. VIMOVO The Company is required to pay Aralez Pharmaceuticals Inc. (“Aralez”) a ten percent royalty on net sales of VIMOVO and other medicines sold by the Company, its affiliates or sublicensees during the royalty term that contain gastroprotective agents in a single fixed combination oral solid dosage form with nonsteroidal anti-inflammatory drugs, subject to minimum annual royalty obligations of $7.5 million. These minimum royalty obligations will continue for each year during which one of Aralez’s patents covers such medicines in the United States and there are no competing medicines in the United States. The royalty rate may be reduced to a mid-single digit royalty rate as a result of loss of market share to competing medicines. The Company’s obligation to pay royalties to Aralez will expire upon the later of (a) expiration of the last-to-expire of certain patents covering such medicines in the United States, and (b) ten years after the first commercial sale of such medicines in the United States. The royalty obligations described above are included in accrued royalties on the Company’s consolidated balance sheets. For all of the royalty agreements entered into by the Company, a total expense of $82.3 million was recorded during the year ended December 31, 2017, of which $81.6 million was recorded in “cost of goods sold” and $0.7 million was recorded in “selling, general and administrative” expenses in the consolidated statements of comprehensive loss. During the year ended December 31, 2016 and 2015, a total expense of $46.5 million and $45.5 million, respectively, was recorded in cost of goods sold in the consolidated statements of comprehensive loss. Other Agreements On November 8, 2016, the Company entered into a collaboration and option agreement with a privately held life-science entity. Under the terms of the agreement, the privately held life-science entity will conduct certain research and pre-clinical and clinical development activities. Upon execution of the agreement, the Company paid $0.1 million for the option to acquire certain of the privately held life-science entity’s assets for $25.0 million, which is exercisable on specified key dates. Under the collaboration and option agreement, the Company is required to pay up to $9.8 million upon the attainment of various milestones, primarily to fund clinical development costs for the medicine candidate. The Company paid an aggregate of $2.6 million in relation to these milestones during the years ended December 31, 2017 and 2016. On May 8, 2017, the Company acquired River Vision for upfront cash payments totaling approximately $150.3 million, including cash acquired of $6.3 million, and potential future milestone and royalty payments contingent on the satisfaction of certain regulatory milestones and sales thresholds. Under the agreement, the Company is required to pay up to $325.0 million upon the attainment of various milestones related to FDA approval and net sales thresholds. The agreement also includes a royalty payment of three percent of the portion of annual worldwide net sales exceeding $300.0 million (if any). Under a separate agreement, the Company is also required to pay up to CHF103.0 million upon the attainment of various milestones related to approval, filing and net sales thresholds. During the year ended December 31, 2017, CHF2.0 million was paid in relation to these milestones. The agreement also includes a royalty payment of between nine percent and twelve percent of the portion of annual worldwide net sales. On December 12, 2017, the Company entered into an agreement to license HZN-003 (formerly MEDI4945), a rheumatology pipeline program with the objective of enhancing the Company’s leadership position in the uncontrolled gout market, from MedImmune. Under the terms of the agreement, the Company paid MedImmune an upfront cash payment of $12.0 million. Under the license agreement, the Company is required to pay up to $153.5 million upon the attainment of various milestones linked to the initiation of clinical trials and the attainment of net sales thresholds, and royalties on net sales. Contingencies The Company is subject to claims and assessments from time to time in the ordinary course of business. The Company’s management does not believe that any such matters, individually or in the aggregate, will have a material adverse effect on the Company’s business, financial condition, results of operations or cash flows. In addition, the Company from time to time has billing disputes with vendors in which amounts invoiced are not in accordance with the terms of their contracts. In November 2015, the Company received a subpoena from the U.S. Attorney’s Office for the Southern District of New York requesting documents and information related to its patient access programs and other aspects of its marketing and commercialization activities. The Company is unable to predict how long this investigation will continue or its outcome, but it anticipates that it will continue to incur significant costs in connection with the investigation, regardless of the outcome. The Company may also become subject to similar investigations by other governmental agencies. The investigation by the U.S. Attorney’s Office and any additional investigations of the Company’s patient access programs and sales and marketing activities may result in damages, fines, penalties or other administrative sanctions against the Company. Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. In connection with the federal securities class action litigation (described in Note 19 below), the Company has received notice from the Underwriter Defendants (as defined below) of their intention to seek indemnification and has received and paid several invoices from the Underwriter Defendants. On November 14, 2016, all defendants moved to dismiss the plaintiffs’ amended complaint. Plaintiffs filed their opposition to the motion to dismiss on December 21, 2016. On January 18, 2018, the District Court dismissed all Plaintiffs’ claims against all Defendants, and denied the Plaintiffs any further opportunity to amend their complaint. On February 16, 2018, plaintiffs filed a notice of appeal to the District Court’s ruling. The Company may record charges in the future as a result of these indemnification obligations. In accordance with its memorandum and articles of association, the Company has indemnification obligations to its officers and directors for certain events or occurrences, subject to certain limits, while they are serving at the Company’s request in such capacity. Additionally, the Company has entered into, and intends to continue to enter into, separate indemnification agreements with its directors and executive officers. These agreements, among other things, require the Company to indemnify its directors and executive officers for certain expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by a director or executive officer in any action or proceeding arising out of their services as one of the Company’s directors or executive officers, or any of the Company’s subsidiaries or any other company or enterprise to which the person provides services at the Company’s request. In connection with the federal securities class action litigation (described in Note 19 below), the Company has paid legal fees and costs on behalf of itself and the current and former officers and directors of the Company who are named as defendants in that litigation. The Company also has a director and officer insurance policy that enables it to recover a portion of any amounts paid for current and future potential claims. All of the Company’s officers and directors have also entered into separate indemnification agreements with HPI.

Legal Proceedings

Legal Proceedings	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Legal Proceedings	NOTE 19 - LEGAL PROCEEDINGS RAVICTI On March 17, 2014, Hyperion received notice from Par Pharmaceutical, Inc. (“Par Pharmaceutical”) that it had filed an ANDA with the FDA seeking approval for a generic version of the Company’s medicine RAVICTI. The ANDA contained a Paragraph IV Patent Certification alleging that two of the patents covering RAVICTI, U.S. Patent No. 8,404,215, titled “Methods of therapeutic monitoring of nitrogen scavenging drugs,” which expires in March 2032 (the “’215 patent”), and U.S. Patent No. 8,642,012, titled “Methods of treatment using ammonia scavenging drugs,” which expires in September 2030 (the “’012 patent”), are invalid and/or will not be infringed by Par Pharmaceutical’s manufacture, use or sale of the medicine for which the ANDA was submitted. Par Pharmaceutical did not challenge the validity, enforceability, or infringement of the Company’s primary composition of matter patent for RAVICTI, U.S. Patent No. 5,968,979 titled “Triglycerides and ethyl esters of phenylalkanoic acid and phenylalkanoic acid useful in treatment of various disorders,” which would have expired on February 7, 2015, but as to which Hyperion was granted an interim term of extension until February 7, 2016 and to which the U.S. PTO has granted a final term extension of 1,267 days, which extends the expiration date to July 28, 2018. Hyperion filed suit in the United States District Court for the Eastern District of Texas, Marshall Division, against Par Pharmaceutical on April 23, 2014 seeking an injunction to prevent the approval of Par Pharmaceutical’s ANDA and/or to prevent Par Pharmaceutical from selling a generic version of RAVICTI, and the Company has taken over and is responsible for this patent litigation. On September 15, 2015, the Company received notice from Par Pharmaceutical that it had filed a Paragraph IV Patent Certification alleging that U.S. Patent No. 9,095,559 (the “’559 patent”) is invalid and/or will not be infringed by Par Pharmaceutical’s manufacture, use or sale of the medicine for which the ANDA was submitted. On March 14, 2016, the Company received notice from Par Pharmaceutical that it had filed a Paragraph IV Patent Certification alleging that U.S. Patent No. 9,254,278 (the “’278 patent”) is invalid and/or will not be infringed by Par Pharmaceutical’s manufacture, use or sale of the medicine for which the ANDA was submitted. On June 3, 2016, the Company received notice from Par Pharmaceutical that it had filed a Paragraph IV Patent Certification alleging that U.S. Patent No. 9,326,966 (the “’966 patent”) is invalid and/or will not be infringed by Par Pharmaceutical’s manufacture, use or sale of the medicine for which the ANDA was submitted. The Company filed suit in the United States District Court for the District of New Jersey against Par Pharmaceutical on June 30, 2016 (the “Par New Jersey action”), seeking an injunction to prevent the approval of Par Pharmaceutical’s ANDA and/or to prevent Par Pharmaceutical from selling a generic version of RAVICTI. The lawsuit alleges that Par Pharmaceutical has infringed the ’559 patent, the ’278 patent and the ’966 patent by filing an ANDA seeking approval from the FDA to market generic versions of RAVICTI prior to the expiration of the patents. The subject patents are listed in the Orange Book. The Par New Jersey action has been stayed pending the resolution of the PTAB’s IPR of the ’559 patent. On April 29, 2015, Par Pharmaceutical filed Petitions for IPR of U.S. Patent 8,404,215 and U.S. Patent 8,642,012, two of the patents involved in the above mentioned RAVICTI cases. On November 4, 2015, the PTAB issued decisions instituting such IPRs. On September 29, 2016, the PTAB found all of the claims in U.S. Patent 8,404,215 to be unpatentable. The Company did not appeal the PTAB’s final written decision with respect to U.S. Patent 8,404,215. On November 3, 2016, the PTAB issued a final written decision holding all of the claims of U.S. Patent 8,642,012 patentable. U.S. Patent 8,642,012. On April 1, 2016, Lupin filed a Petition for IPR of U.S. Patent 9,095,559, a patent currently at issue in the Lupin RAVICTI case. On September 30, 2016, the PTAB issued a decision instituting the IPR. On September 26, 2017, the PTAB issued its final written decision, ruling that the challenged claims of the ‘559 patent are unpatentable. The Company filed a Notice of Appeal on November 22, 2017. On July 13, 2017, Par Pharmaceutical filed Petitions for IPR of the ‘559, ‘278, and ‘966 patents. The Company filed its Preliminary Patent Owner Responses on November 6, 2017. The IPR requests were granted on January 30, 2018. On August 8, 2017, the Company filed suit against Lupin and Par Pharmaceutical, alleging infringement of U.S. Patent No. 9,561,197 (“the ‘197 Patent”), in the United States District Court for New Jersey, Case Nos. 1:17-cv-05900 and 1:17-cv-05901, respectively. Par Pharmaceutical and Lupin have answered and counterclaimed. On January 12, 2018, Lupin filed a petition for IPR (IPR 2018-00459) of the ‘197 Patent. The Company’s Preliminary Patent Owner Response is due by April 12, 2018. RAYOS On July 15, 2013, the Company received a Paragraph IV Patent Certification from Teva Pharmaceuticals Industries Limited (formerly known as Actavis Laboratories FL, Inc., which itself was formerly known as Watson Laboratories, Inc. – Florida) (“Teva”), advising that Teva had filed an Abbreviated New Drug Application (“ANDA”) with the FDA for a generic version of RAYOS, containing up to 5 mg of prednisone. On August 26, 2013, the Company, together with Jagotec, filed suit in the United States District Court for the District of New Jersey against Teva, Actavis Pharma, Inc., Andrx Corp., and Actavis, Inc. seeking an injunction to prevent the approval of the ANDA. On October 1, 2015, the Company’s subsidiary Horizon Pharma Switzerland GmbH, as well as Jagotec, entered into a license and settlement agreement (the “Teva settlement agreement”) with Teva relating to the Company’s and Jagotec’s patent infringement litigation against Teva. Under the Teva settlement agreement, the Company and Jagotec granted Teva a non-exclusive license to manufacture and commercialize Teva’s generic version of RAYOS tablets in the United States after December 23, 2022 (the “Teva generic entry date”); however, Teva may be able to enter the market earlier under certain circumstances. Such events relate to the resolution of any other third-party RAYOS patent litigation, the entry of other generic versions of RAYOS tablets or certain substantial reductions in RAYOS prescriptions over specified periods of time. The Company and Jagotec also agreed that during the 180 days after the Teva generic entry date, the license granted to Teva would be exclusive with respect to any third-party generic version of RAYOS tablets. The court entered the stipulation of dismissal and closed the case on December 4, 2015. PENNSAID 2% On November 13, 2014, the Company received a Paragraph IV Patent Certification from Watson Laboratories, Inc., now known as Actavis Laboratories UT, Inc. (“Actavis UT”), advising that Actavis UT had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On December 23, 2014, the Company filed suit in the United States District Court for the District of New Jersey against Actavis Laboratories UT, Inc., and Actavis plc (collectively “Actavis”) seeking an injunction to prevent the approval of the ANDA. The lawsuit alleged that Actavis has infringed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, and 8,871,809 by filing an ANDA seeking approval from the FDA to market a generic version of PENNSAID 2% prior to the expiration of certain of the Company’s patents listed in the FDA’s Orange Book (“Orange Book”). On June 30, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patent 9,066,913. On August 11, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patent 9,101,591. On September 17, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patent 9,132,110. These three cases were consolidated with the case filed against Actavis on December 23, 2014. On October 27, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patents 9,168,304 and 9,168,305. On February 5, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patent No. 9,220,784. On August 17, 2016, the district court issued a Markman opinion holding certain of the asserted claims of U.S. Patents 8,252,838, 8,563,613, 9,066,913, 9,101,591, 9,168,304, 9,168,305, and 9,220,784 invalid as indefinite. On March 16, 2017, the court granted Actavis’ motion for summary judgment of non-infringement of the asserted claims of U.S. Patents 8,546,450, 8,217,078 and 9,132,110. In view of the Markman On August 18, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Actavis for patent infringement of U.S. Patents 9,339,551, 9,339,552, 9,370,501 and 9,375,412. All four patents of such patents are listed in the Orange Book and have claims that cover PENNSAID 2%. This litigation is currently stayed by agreement of the parties. The Company received from Actavis a Paragraph IV Patent Certification Notice Letter dated September 27, 2016, against Orange Book listed U.S. Patent No. 9,415,029, advising that Actavis had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On December 2, 2014, the Company received a Paragraph IV Patent Certification against Orange Book listed U.S. Patents. 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164 and 8,741,956 from Paddock Laboratories, LLC (“Paddock”) advising that Paddock had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On January 9, 2015, the Company received from Paddock another Paragraph IV Patent Certification against newly Orange Book listed U.S. Patent No. 8,871,809. On January 13, 2015 and January 14, 2015, the Company filed suits in the United States District Court for the District of New Jersey and the United States District Court for the District of Delaware, respectively, against Paddock seeking an injunction to prevent the approval of the ANDA. On May 6, 2015, the Company entered into a settlement and license agreement (the “Perrigo settlement agreement”) with Perrigo Company plc and its subsidiary Paddock (collectively, “Perrigo”). The Perrigo settlement agreement provides for a full settlement and release by both the Company and Perrigo of all claims that were or could have been asserted in the litigation and that arise out of the issues that were the subject of the litigation or Perrigo’s generic version of PENNSAID 2%. A stipulation of dismissal was entered by the district court on May 13, 2015. Under the Perrigo settlement agreement, the Company granted Perrigo a non-exclusive license to manufacture and commercialize Perrigo’s generic version of PENNSAID 2% in the United States after In certain circumstances following the entry of other third-party generic versions of PENNSAID 2%, the Company may be required to supply Perrigo PENNSAID 2% as its authorized distributor of generic PENNSAID 2%, with the Company receiving specified percentages of any net sales by Perrigo. On February 2, 2015, the Company received a Paragraph IV Patent Certification against Orange Book listed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, 8,741,956 and 8,871,809 from Taro Pharmaceuticals USA, Inc. and Taro Pharmaceutical Industries, Ltd. (collectively, “Taro”) advising that Taro had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On March 13, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Taro seeking an injunction to prevent the approval of the ANDA. On September 9, 2015, certain subsidiaries of the Company (the “Horizon Subsidiaries”) entered into a settlement and license agreement with Taro (the “Taro settlement agreement”) relating to the Horizon Subsidiaries’ patent infringement litigation against Taro. The Taro settlement agreement provides for a full settlement and release by the Horizon Subsidiaries and Taro of all claims that were or could have been asserted in the litigation and that arise out of the issues that were subject of the litigation or Taro’s generic version of PENNSAID 2%. A stipulation of dismissal was entered by the district court on November 3, 2015. Under the Taro settlement agreement, the Horizon Subsidiaries granted Taro a non-exclusive license to manufacture and commercialize Taro’s generic version of PENNSAID 2% in the United States after On March 18, 2015, the Company received a Paragraph IV Patent Certification against Orange Book listed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, 8,741,956 and 8,871,809 from Lupin Limited advising that Lupin Limited had filed an ANDA with the FDA for generic version of PENNSAID 2%. On April 30, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Lupin Limited and Lupin Pharmaceuticals Inc. (collectively, “Lupin”), seeking an injunction to prevent the approval of the ANDA. The lawsuit alleges that Lupin has infringed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164 and 8,871,809 by filing an ANDA seeking approval from the FDA to market generic versions of PENNSAID 2% prior to the expiration of certain of the Company’s patents listed in the Orange Book. On June 30, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Lupin for patent infringement of U.S. Patent No. 9,066,913. On August 11, 2015, the Company filed an amended complaint in the United States District Court for the District of New Jersey against Lupin that added U.S. Patent No. 9,101,591 to the litigation concerning U.S. Patent 9,066,913. On September 17, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Lupin for patent infringement of U.S. Patent 9,132,110. On October 27, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Lupin for patent infringement of U.S. Patents 9,168,304 and 9,168,305. On February 5, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Lupin for patent infringement of U.S. Patent No. 9,220,784. On August 18, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Lupin for patent infringement of U.S. Patents 9,339,551, 9,339,552, 9,370,501 and 9,375,412. All seven patents, U.S. Patents 9,168,304, 9,168,305, 9,220,784, 9,339,551, 9,339,552, 9,370,501 and 9,375,412, are listed in the Orange Book and have claims that cover PENNSAID 2%. All of the infringement actions brought against Lupin remain pending, with certain claims of the ’809, ’913, ’450, ’110, ’551, ’552, ’412 and ’501 patents being asserted. The decisions reached by the court in the related Actavis actions regarding the ‘809, ‘913, ‘450, ‘110, ‘551, ‘552, ‘412 and ‘501 patents as described above, are expected to apply to the same claims asserted against Lupin in these actions. The court has not yet set a trial date for the Lupin actions. The Company received from Teligent, Inc., formerly known as IGI Laboratories, Inc. (“Teligent”), a Paragraph IV Patent Certification dated March 24, 2015 against Orange Book listed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, 8,741,956 and 8,871,809 advising that Teligent had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On May 21, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Teligent seeking an injunction to prevent the approval of the ANDA. The lawsuit alleged that Teligent has infringed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164 and 8,871,809 by filing an ANDA seeking approval from the FDA to market generic versions of PENNSAID 2% prior to the expiration of certain of the Company’s patents listed in the Orange Book. On June 30, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Teligent for patent infringement of U.S. Patent 9,066,913. On August 11, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Teligent for patent infringement of U.S. Patent 9,101,591. On September 17, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Teligent for patent infringement of U.S. Patent No. 9,132,110. On October 27, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Teligent for patent infringement of U.S. Patents 9,168,304 and 9,168,305. On February 5, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Teligent for patent infringement of U.S. Patent 9,220,784. The Company entered into a settlement and license agreement with Teligent (the “Teligent settlement agreement”), effective May 9, 2016, relating to the patent infringement litigation against Teligent. The Teligent settlement agreement provides for a full settlement and release by both the Company and Teligent of all claims that were or could have been asserted in the litigation and that arise out of the issues that were subject of the litigation or Teligent’s generic version of PENNSAID 2%. A stipulation of dismissal was entered by the district court on May 2, 2016. Under the Teligent settlement agreement, the Company granted Teligent a non-exclusive license to manufacture and commercialize Teligent’s generic version of PENNSAID 2% in the United States after January 10, 2029; however, Teligent may be able to enter the market earlier under certain circumstances. Such events relate to the resolution of any other third-party PENNSAID 2% patent litigation, the entry of other third-party generic versions of PENNSAID 2% or certain substantial reductions in the Company’s PENNSAID 2% shipments over specified periods of time. In certain circumstances following the entry of other third-party generic versions of PENNSAID 2%, the Company may be required to supply Teligent PENNSAID 2% as an authorized distributor of generic PENNSAID 2%, with the Company receiving specified percentages of any net sales by Teligent. The Company received from Amneal Pharmaceuticals LLC (“Amneal”) a Paragraph IV Patent Certification dated April 2, 2015 against Orange Book listed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, 8,741,956 and 8,871,809 advising that Amneal had filed an ANDA with the FDA for a generic version of PENNSAID 2%. On May 15, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Amneal seeking an injunction to prevent the approval of the ANDA. The lawsuit alleged that Amneal has infringed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164 and 8,871,809 by filing an ANDA seeking approval from the FDA to market generic versions of PENNSAID 2% prior to the expiration of certain of the Company’s patents listed in the Orange Book. On June 30, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Amneal for patent infringement of U.S. Patent 9,066,913. On August 11, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Amneal for patent infringement of U.S. Patent 9,101,591. On September 17, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Amneal for patent infringement of U.S. Patent 9,132,110. All three patents, U.S. Patents 9,066,913, 9,101,591 and 9,132,110, are listed in the Orange Book and have claims that cover PENNSAID 2%. On October 27, 2015, the Company filed suit in the United States District Court for the District of New Jersey against Amneal for patent infringement of U.S. Patents 9,168,304 and 9,168,305. On February 5, 2016, the Company filed suit in the United States District Court for the District of New Jersey against Amneal for patent infringement of U.S. Patent 9,220,784. All three patents, U.S. Patents 9,168,304, 9,168,305, and 9,220,784, are listed in the Orange Book and have claims that cover PENNSAID 2%. On April 18, 2016, the Company entered into a settlement and license agreement (the “Amneal settlement agreement”) with Amneal relating to the Company’s patent infringement litigation against Amneal. The Amneal settlement agreement provides for a full settlement and release by both the Company and Amneal of all claims that were or could have been asserted in the litigation and that arise out of the issues that were the subject of the litigation or Amneal’s generic version of PENNSAID 2%. Under the Amneal settlement agreement, the Company granted Amneal a non-exclusive license to manufacture and commercialize Amneal’s generic version of PENNSAID 2% in the United States after January 10, 2029; however, Amneal may be able to enter the market earlier under certain circumstances. Such events relate to the resolution of any other third-party PENNSAID 2% patent litigation or the entry of other third-party generic versions of PENNSAID 2% and to take steps necessary to develop inventory of, and prepare to commercialize, Amneal’s generic version of PENNSAID 2% during certain limited periods prior to the license effective date. In certain circumstances following the entry of other third-party generic versions of PENNSAID 2%, the Company may be required to supply Amneal with PENNSAID 2% as a non-exclusive, authorized distributor of generic PENNSAID 2%, with the Company receiving specified percentages of any net sales by Amneal. The Company received from Apotex Inc. (“Apotex”) a Paragraph IV Patent Certification Notice Letter dated April 1, 2016, against Orange Book listed U.S. Patents 8,217,078, 8,252,838, 8,546,450, 8,563,613, 8,618,164, 8,741,956, 8,871,809, 9,066,913, 9,101,591, 9,132,110, 9,168,304, 9,168,305 and 9,220,784 advising that Apotex had filed an ANDA with the FDA for a generic version of PENNSAID 2%. The Company also received from Apotex a second Paragraph IV Patent Certification Notice Letter dated June 30, 2016, against Orange Book listed U.S. Patents 9,339,551 and 9,339,552, advising that Apotex had filed an ANDA with the FDA for a generic version of PENNSAID 2%. The Company also received from Apotex a third Paragraph IV Patent Certification Notice Letter dated September 21, 2016, against Orange Book listed U.S. Patent 9,415,029, advising that Apotex had filed an ANDA with the FDA for a generic version of PENNSAID 2%. The Company also received from Apotex additional Paragraph IV Patent Certification Notice Letters dated April 20, 2017 and April 27, 2017 against Orange Book listed U.S. Patent 9,539,335 and 9,370,501. VIMOVO Currently, patent litigation is pending in the United States District Court for the District of New Jersey and the Court of Appeals for the Federal Circuit against three generic companies intending to market VIMOVO prior to the expiration of certain of the Company’s patents listed in the Orange Book. These cases are in the United States District Court for the District of New Jersey. They are collectively known as the VIMOVO cases, and involve the following sets of defendants: (i) Dr. Reddy’s Laboratories Inc. and Dr. Reddy’s Laboratories Ltd. (collectively, “Dr. Reddy’s”); (ii) Lupin; and (iii) Mylan Pharmaceuticals Inc., Mylan Laboratories Limited, and Mylan Inc. (collectively, “Mylan”). Patent litigation in the United States District Court for the District of New Jersey against a fourth generic company, Actavis Laboratories FL., Inc. and Actavis Pharma, Inc. (collectively, “Actavis Pharma”), was dismissed on January 10, 2017 after the court granted Actavis’ motion to compel enforcement of a settlement agreement. On February 3, 2017, the Company appealed this dismissal decision to the Court of Appeals for the Federal Circuit. Patent litigation in the United States District Court for the District of New Jersey against a fifth generic company, Anchen Pharmaceuticals Inc. (“Anchen”), was dismissed on June 9, 2014 after Anchen recertified under Paragraph III. The Company understands that Dr. Reddy’s has entered into a settlement with AstraZeneca with respect to patent rights directed to Nexium ® The VIMOVO cases were filed on April 21, 2011, July 25, 2011, October 28, 2011, January 4, 2013, May 10, 2013, June 28, 2013, October 23, 2013, May 13, 2015 and November 24, 2015 and collectively include allegations of infringement of U.S. Patent Nos. 6,926,907, 8,557,285, 8,852,636, and 8,858,996 (the “’996 patent”). On June 18, 2015, the Company amended the complaints to add a charge of infringement of U.S. Patent No. 8,865,190 (the “’190 patent”). On January 7, 2016, Actavis Pharma asserted a counterclaim for declaratory judgment of invalidity and non-infringement of U.S. Patent No. 8,945,621 (the “’621 patent”). On January 25, 2016, the Company filed a new case against Actavis Pharma including allegations of infringement of U.S. Patent Nos. 9,161,920 and 9,198,888. This case was subsequently consolidated with the Actavis Pharma case involving the ’996 patent, the ’190 patent and U.S. Patent No. 8,852,636. On February 10, 2016, the Company amended the complaints against Dr. Reddy’s, Lupin, and Mylan to add charges of infringement of U.S. Patent Nos. 9,161,920 and 9,198,888. On February 19, 2016, Mylan asserted a counterclaim for declaratory judgment of invalidity and non-infringement of U.S. Patent No. 9,220,698. On August 11, 2016, the Company filed new complaints asserting the ’621 patent and U.S. Patent Nos. 9,220,698, and 9,345,695 against the defendants. On December 6, 2016, the Company asserted U.S. Patent No. 9,393,208 (the “’208 patent”) against Lupin, Mylan, and Actavis in amended complaints, and against Dr. Reddy’s in a new complaint. “Case I” consists of the cases asserting U.S. Patent Nos. 8,557,285 and 6,926,907. “Case II” consists of the cases asserting the ’996 patent, the ’190 patent and U.S. Patent Nos. 8,852,636, 9,161,920, and 9,198,888. “Case III” consists of the cases asserting U.S. Patent Nos. 8,945,621, 9,220,698, 9,345,695, and the ’208 patent against Lupin and Mylan, and the case asserting U.S. Patent Nos. 8,945,621, 9,220,698, 9,345,695, and the ‘208 patent against Dr. Reddy’s. On December 19, 2016, defendant Actavis filed a motion to compel enforcement of settlement agreement related to Cases I, II, and III. On December 22, 2016, Magistrate Judge Arpert entered a report and recommendation that Actavis’ motion to compel the enforcement of settlement be granted. On December 30, 2016, the Honorable Judge Mary Cooper ordered the adoption of the report and recommendation. On January 10, 2017, an order of dismissal was entered for all claims in Cases I, II and III. The Company appealed the district court’s order enforcing the settlement with Actavis to the Court of Appeals for the Federal Circuit. Briefing before the Federal Circuit has been completed. The Case I cases were consolidated for discovery. The court issued a claim construction order for Case I and conducted trial beginning on January 12, 2017. On May 12, 2016, the court granted Dr. Reddy’s motion for summary judgment of non-infringement of U.S. Patent No. 6,926,907 with respect to one of Dr. Reddy’s two ANDAs. On January 12, 2017, a six-day bench trial commenced against defendants Dr. Reddy’s and Mylan before Honorable Judge Mary Cooper in the District of New Jersey for Case I. The patents at issue in this trial included two Orange Book listed patents: U.S. Patent Nos. 6,926,907 and 8,557,285. Defendant Lupin formerly entered into a stay pending the entry of judgment in Case I. On June 26, 2017, the court issued its opinion upholding the validity of the ‘285 and ‘907 patents and finding that Dr. Reddy’s, Mylan’s, and Lupin’s proposed generic naproxen/esomeprazole magnesium products would all infringe at least one of the two patents. The court entered the final judgment on July 21, 2017. Dr. Reddy’s, Mylan and Lupin appealed the District Court’s judgment to the Court of Appeals for the Federal Circuit, and the Company appealed the District Court’s entry of judgment of non-infringement on the ‘907 in favor of Dr. Reddy’s. The Case II and Case III cases have been consolidated for discovery. On January 19, 2017, the court entered a scheduling order for Case II and Case III, which was subsequently updated. The court’s scheduling order requires, inter alia On June 5, 2015, the Coalition for Affordable Drugs VII LLC (“Coalition for Affordable Drugs”) filed a Petition for inter partes review (“IPR”) of the ’996 patent, one of the patents in litigation in the above referenced VIMOVO cases. On December 17, 2015, the United States Patent and Trademark Office (the “U.S. PTO”) denied such Petition for IPR. On August 7, 2015, the Coalition for Affordable Drugs filed another Petition for IPR of U.S. Patent No. 8,852,636, one of the patents in litigation in the above referenced VIMOVO cases. On February 11, 2016, the U.S. PTO denied such Petition for IPR. On August 12, 2015, the Coalition for Affordable Drugs filed another Petition for IPR of the ’621 patent, one of the patents in litigation in the above referenced VIMOVO cases. On February 22, 2016, the Patent Trial and Appeal Board (the “PTAB”) issued a decision to institute the IPR. The PTAB hearing for the ‘621 patent was held on November 16, 2016. The PTAB issued a final written decision finding the ’621 patent valid on February 21, 2017. On August 19, 2015, Lupin filed Petitions for IPR of the ’996 patent, the ’190 patent and U.S. Patent No. 8,852,636, all patents in litigation in the above referenced VIMOVO cases. On March 1, 2016, the PTAB issued decisions to institute the IPRs for the ’996 patent” and the ’190 patent. On March 1, 2016, the PTAB denied the Petition for IPR for U.S. Patent No. 8,852,636. The PTAB hearings for the ‘996 patent and ‘190 patent were both held on November 29, 2016. On February 28, 2017, the PTAB issued final written decisions on the IPRs of the ‘996 and ‘190 patents, upholding the validity of both patents. On August 24, 2017, Mylan filed a Petition for IPR of the ‘698 patent. The Company filed its Preliminary Patent Owner Response on December 12, 2017. The parties are awaiting the PTAB’s decision on whether to institute an IPR proceeding. On December 4, 2017, Mylan filed a Petition for IPR of the ‘208 patent. The Company’s Preliminary Patent Owner Response is due on March 4, 2018. Other Beginning on March 8, 2016, two federal securities class action lawsuits (captioned Schaffer v. Horizon Pharma plc, et al., Case No. 16-cv-01763-JMF and Banie v. Horizon Pharma plc, et al., Case No. 16-cv-01789-JMF) were filed in the United States District Court for the Southern District of New York against the Company and certain of the Company’s current and former officers (the “Officer Defendants”). On March 24, 2016, the court consolidated the two actions under Schaffer v. Horizon Pharma plc, et al. On June 3, 2016, the court appointed Locals 302 and 612 of the International Union of Operating Engineers-Employers Construction Industry Retirement Trust and the Carpenters Pension Trust Fund for Northern California as lead plaintiffs and Labaton Sucharow LLP as lead counsel. On July 25, 2016, lead plaintiffs and additional named plaintiff Automotive Industries Pension Trust Fund filed their consolidated complaint, which they subsequently amended on October 7, 2016, including additional current and former officers, the Company’s Board of Directors (the “Director Defendants”), and underwriters involved with the Company’s April 2015 public offering (the “Underwriter Defendants”) as defendants. The plaintiffs allege that certain of the Company and the Officer Defendants violated sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, by making false and/or misleading statements about, among other things: (a) the Company’s financial performance, (b) the Company’s busi

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Shareholders' Equity	NOTE 20 – SHAREHOLDERS’ EQUITY During the year ended December 31, 2017, the Company issued an aggregate of 2.0 million of ordinary shares in connection with stock option exercises, the vesting of restricted stock units, employee share purchase plan purchases and the vesting of performance stock units. The Company received a total of $9.2 million in net proceeds in connection with such issuances. During the year ended December 31, 2017, the Company issued an aggregate of 391,500 ordinary shares upon the cash exercise of warrants and the Company received proceeds of $1.8 million representing the aggregate exercise price for such warrants. In addition, warrants to purchase an aggregate of 704,285 ordinary shares of the Company were exercised in cashless exercises, resulting in the issuance of 523,520 ordinary shares. As of December 31, 2017, there were no outstanding warrants to purchase ordinary shares of the Company. During the year December 31 6.5 On January 1, 2017, the Company adopted ASU No. 2016-09. As a result of the adoption, $7.2 million of excess tax benefits that had not previously been recognized, as the related tax deduction had not reduced current taxes payable, were recorded on a modified retrospective basis through a cumulative effect adjustment to its accumulated deficit as of January 1, 2017. In May 2016, the Company’s board of directors authorized a share repurchase program pursuant to which the Company may repurchase up to 5,000,000 of its ordinary shares. In May 2017, the Company’s board of directors reauthorized a share repurchase program pursuant to which the Company may repurchase up to 16,000,000 of its ordinary shares. As of December 31, 2017, the Company had repurchased 100,000 of its ordinary shares under this repurchase program, for total consideration of $1.0 million. The timing and amount of future repurchases, if any, will depend on a variety of factors, including the price of the Company’s ordinary shares, alternative investment opportunities, the Company’s cash resources, restrictions under the Credit Agreement and market conditions.

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans	NOTE 21 – EQUITY INCENTIVE PLANS Employee Stock Purchase Plan 2014 Employee Stock Purchase Plan . On May 17, 2014, HPI’s board of directors adopted the 2014 Employee Stock Purchase Plan (the “2014 ESPP”). On September 18, 2014, at a special meeting of the stockholders of HPI (the “Special Meeting”), HPI’s stockholders approved the 2014 ESPP. Upon consummation of the Company’s merger transaction with Vidara (the “Vidara Merger”), the Company assumed the 2014 ESPP. As of December 31, 2017, an aggregate of 3,002,169 ordinary shares were authorized and available for future issuance under the 2014 ESPP. Share-Based Compensation Plans 2005 Stock Plan . In October 2005, HPI adopted the 2005 Stock Plan (the “2005 Plan”). Upon the signing of the underwriting agreement related to HPI’s initial public offering, on July 28, 2011, no further option grants were made under the 2005 Plan. All stock awards granted under the 2005 Plan prior to July 28, 2011 continue to be governed by the terms of the 2005 Plan. Upon consummation of the Vidara Merger, the Company assumed the 2005 Plan. 2011 Equity Incentive Plan . In July 2010, HPI’s board of directors adopted the 2011 Equity Incentive Plan (the “2011 EIP”). In June 2011, HPI’s stockholders approved the 2011 EIP, and it became effective upon the signing of the underwriting agreement related to HPI’s initial public offering on July 28, 2011. Upon consummation of the Vidara Merger, the Company assumed the 2011 EIP, and upon the effectiveness of the Horizon Pharma Public Limited Company 2014 Equity Incentive Plan (the “2014 EIP”), no additional stock awards were or will be made under the 2011 Plan, although all outstanding stock awards granted under the 2011 Plan continue to be governed by the terms of the 2011 Plan. 2014 Equity Incentive Plan and 2014 Non-Employee Equity Plan . On May 17, 2014, HPI’s board of directors adopted the 2014 EIP and the Horizon Pharma Public Limited Company 2014 Non-Employee Equity Plan (the “2014 Non-Employee Equity Plan”). At the Special Meeting, HPI’s stockholders approved the 2014 EIP and 2014 Non-Employee Equity Plan. Upon consummation of the Vidara Merger, the Company assumed the 2014 EIP and 2014 Non-Employee Equity Plan, which serve as successors to the 2011 EIP. The 2014 EIP provides for the grant of incentive and nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards and other stock awards that may be settled in cash, shares or other property to the employees of the Company (or a subsidiary company). During the year ended December 31, 2017, the compensation committee of the Company’s board of directors (the “Committee”) approved an amendment to the 2014 EIP to reserve additional shares to be used exclusively for grants of awards to individuals who were not previously employees or non-employee directors of the Company (or following a bona fide period of non-employment with the Company) (the “2017 Inducement Pool”), as an inducement material to the individual’s entry into employment with the Company within the meaning of Rule 5635(c)(4) of the NASDAQ Listing Rules, (“Rule 5635(c)(4)”). The 2014 EIP was amended by the Committee without shareholder approval pursuant to Rule 5635(c)(4). The 2014 Non-Employee Equity Plan provides for the grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other forms of stock awards that may be settled in cash, shares or other property to the non-employee directors and consultants of the Company (or a subsidiary company). The Company’s board of directors has authority to suspend or terminate the 2014 Non-Employee Equity Plan at any time. As of December 31, 2017, an aggregate of 3,885,178 ordinary shares were authorized and available for future grants under the 2014 EIP, of which 356,636 shares relate to the 2017 Inducement Pool. As of December 31, 2017, 499,913 ordinary shares were authorized and available for future grants under the 2014 Non-Employee Equity Plan. Stock Options The following table summarizes stock option activity during the year ended December 31, 2017: Weighted Average Weighted Contractual Term Aggregate Average Remaining Intrinsic Value Options Exercise Price (in years) (in thousands) Outstanding as of December 31, 2016 13,627,519 $ 18.17 7.60 $ 35,157 Granted 2,077,215 16.40 Exercised (338,467 ) 6.27 Forfeited (644,752 ) 18.37 Expired (446,199 ) 22.75 Outstanding as of December 31, 2017 14,275,316 18.04 6.97 25,005 Vested and Expected to vest as of December 31, 2017 13,789,210 18.02 6.92 24,960 Exercisable as of December 31, 2017 9,365,306 $ 16.96 6.36 $ 24,158 Stock options typically have a contractual term of ten years from grant date. The following table summarizes the Company’s outstanding stock options at December 31, 2017: Options Outstanding Options Exercisable Weighted Average Weighted Weighted Average Weighted Remaining Average Remaining Number of options Average Contractual Number Exercise Contractual Exercise Price Ranges outstanding Exercise Price Term (in years) Exercisable Price Term (in years) $2.01 - $4.00 742,582 $ 2.67 5.08 742,582 $ 2.67 5.08 $4.01- $8.00 1,209,543 6.29 4.57 1,199,789 6.28 4.56 $8.01 - $12.00 721,063 9.19 5.41 677,499 9.17 5.34 $12.01 - $17.00 2,552,212 14.12 6.87 1,810,195 14.05 6.11 $17.01 - $22.00 3,252,701 18.11 8.33 1,018,088 18.83 7.51 $22.01 - $28.00 3,412,700 22.31 7.24 2,342,100 22.30 7.23 $28.01 - $36.00 2,384,515 29.47 7.14 1,575,053 29.39 7.01 14,275,316 $ 18.04 6.97 9,365,306 $ 16.96 6.36 During the years ended December 31, 2017, 2016 and 2015, the Company granted stock options to purchase an aggregate of 2,077,215, 2,057,247 and 8,010,638 ordinary shares, respectively, with a weighted average grant date fair value of $7.96, $11.58 and $16.07, respectively. The total intrinsic value of the options exercised during the years ended December 31, 2017, 2016 and 2015 was $2.6 million, $6.9 million and $15.6 million, respectively. The total fair value of stock options vested during the years ended December 31, 2017, 2016 and 2015 was $41.3 million, $55.6 million and $11.4 million, respectively. The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. The determination of the fair value of each stock option is affected by the Company’s share price on the date of grant, as well as assumptions regarding a number of highly complex and subjective variables. These variables include, but are not limited to, the Company’s expected share price volatility over the expected life of the awards and actual and projected stock option exercise behavior. The weighted average fair value per share of stock option awards granted during the years ended December 31, 2017, 2016 and 2015, and assumptions used to value stock options, are as follows: 2017 2016 2015 Dividend yield — — — Risk-free interest rate 1.8%-2.2% 1.3%-2.2% 1.3% - 2.2% Weighted average volatility 49.1 % 73.2 % 77.1 % Expected life (in years) 5.99 6.02 6.07 Weighted average grant date fair value per share of options granted $ 7.96 $ 11.58 $ 16.07 Dividend yields The Company has never paid dividends and does not anticipate paying any dividends in the near future. Additionally, the Credit Agreement (described in Note 16 above), as well as the indentures governing the 2024 Senior Notes and the 2023 Senior Notes (each as described in Note 16 above), contain covenants that restrict the Company from issuing dividends. Risk-Free Interest Rate The Company determined the risk-free interest rate by using a weighted average assumption equivalent to the expected term based on the U.S. Treasury constant maturity rate as of the date of grant. Volatility The Company used an average historical share price volatility of comparable companies to be representative of future share price volatility, as the Company did not have sufficient trading history for its ordinary shares. Expected Term Given the Company’s limited historical exercise behavior, the expected term of options granted was determined using the “simplified” method since the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. Under this approach, the expected term is presumed to be the average of the vesting term and the contractual life of the option. Forfeitures As share-based compensation expense recognized in the consolidated statements of comprehensive loss is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures based on actual forfeiture experience, analysis of employee turnover and other factors. The Company adopted ASU No. 2016-09 on January 1, 2017 and has elected to retain a forfeiture rate after adoption. Restricted Stock Units The following table summarizes restricted stock unit activity for the year ended December 31, 2017: Weighted Average Number of Grant-Date Fair Units Value Per Units Outstanding as of December 31, 2016 3,367,871 $ 18.45 Granted 3,732,035 12.44 Vested (1,222,920 ) 16.78 Forfeited (593,136 ) 16.85 Outstanding as of December 31, 2017 5,283,850 $ 14.77 The grant-date fair value of restricted stock units is the closing price of the Company’s shares on the date of grant. During the years ended December 31, 2017, 2016 and 2015, the Company granted 3,732,035, 1,384,104 and 2,361,948 restricted stock units to acquire shares of the Company’s ordinary shares to its employees and non-executive directors, respectively, with a weighted average grant date fair value of $12.44, $17.07 and $23.36, respectively. The restricted stock units vest annually, with a vesting period ranging from two to four years. The Company accounts for the restricted stock units as equity-settled awards in accordance with ASC 718. The total fair value of restricted stock units vested during the years ended December 31, 2017, 2016 and 2015 was $18.0 million, $16.2 million and $9.0 million, respectively. Performance Stock Unit Awards The following table summarizes performance stock unit awards (“PSUs”) activity for the year ended December 31, 2017: Weighted Recorded Average Weighted Grant-Date Average Average Number Fair Value Illiquidity Fair Value of Units Per Unit Discount Per Unit Outstanding as of December 31, 2016 12,045,656 Vested and issued (25,000 ) $ 12.36 0.0 % $ 13.30 Expired (1) (3,927,440 ) 14.82 14.9 % 12.60 Forfeited (238,336 ) 10.86 7.5 % 10.04 Outstanding as of December 31, 2017 7,854,880 (1) During the year ended December 31, 2017, the first of three tranches of the Company’s outstanding PSUs expired due to failure to meet the Company’s minimum total compounded annual shareholder rate of return (“TSR”) requirement. In March 2015, the Committee approved the grant of 10,604,000 PSUs to certain members of the Company’s executive committee, senior leadership team and other key employees. Of these PSUs, 7,998,000 were granted subject to shareholder approval of certain amendments of the 2014 EIP, which occurred on May 6, 2015. In May 2015, the Committee granted 1,264,000 PSUs to new and promoted key employees. In the third and fourth quarters of 2015, the Committee granted 1,120,000 PSUs to a new member of the Company’s executive committee and key employees and 388,000 PSUs to non-executive committee members, respectively. In January 2016, the Committee approved the grant of 260,000 PSUs to certain members of the Company’s senior leadership team. All PSUs outstanding as of December 31, 2017 were granted in 2015 and 2016 and may vest if the Company’s TSR over two performance measurement periods summarized below equals or exceeds a minimum of 15%. Beginning of Length of Percent of Performance Performance Total PSU Measurement End of Performance Measurement Vesting Tranche Award Period Measurement Period Period (Years) Tranche Two 33.3 % March 23, 2015 March 22, 2018 3.00 Tranche Three 33.3 % March 23, 2015 June 22, 2018 3.25 These outstanding PSUs may vest in amounts ranging from 25% to 100% based on the achievement of the following TSR over the two performance periods: TSR Achieved Vesting 15% 25 % 30% 50 % 45% 75 % 60% 100 % The TSR is based on the volume weighted average trading price (“VWAP”) of the Company’s ordinary shares over the twenty trading days ending on the last day of each of the two performance measurement periods versus the VWAP of the Company’s ordinary shares over the twenty trading days ended March 23, 2015 of $21.50. The PSUs are subject to a post-vesting holding period of one year for 50% of the PSUs and two years for 50% of the PSUs for those who were members of the executive committee at the date of grant, and one year for 50% of the PSUs for all who were not executive committee members at the date of grant. The Company accounts for the PSUs as equity-settled awards in accordance with ASC 718. Because the value of the PSUs is dependent upon the attainment of a level of TSR, it requires the impact of the market condition to be considered when estimating the fair value of the PSUs. As a result, the Monte Carlo model is applied and the most significant valuation assumptions used include: For the Years Ended December 31, 2017 2016 2015 Valuation date stock price N/A $ 17.72 - $21.07 $ 16.81 - $35.06 Expected volatility N/A 76.8% - 77.6% 64.6% - 72.3% Risk-free rate N/A 1.0% - 1.2% 1.0% - 1.1% The average estimated fair value of each outstanding PSU is as follows (allocated between groupings based on grant-date classification): Recorded Weighted Weighted Average Fair Average Average Number Value Per Illiquidity Fair Value of Units Unit Discount Per Unit Executive committee members 6,014,437 $ 15.16 17.1 % $ 12.57 Non-executive committee members 1,840,443 13.71 7.3 % 12.71 7,854,880 $ 14.82 14.9 % $ 12.60 During the years ended December 31, 2017, 2016 and 2015, the Company recorded an expense of $49.6 million, $48.6 million and $37.7 million, respectively, related to its PSUs. Cash Long-Term Incentive Program On November 5, 2014, the Committee approved a performance cash long-term incentive program for the members of the Company’s executive committee and executive leadership team, including its executive officers (the “Cash Bonus Program”). Participants in the Cash Bonus Program were eligible for a specified cash bonus. The Cash Bonus Program pool funding of approximately $15.8 million was determined based on the Company’s actual TSR over the period from November 5, 2014 to May 6, 2015, and the bonus could be earned and payable only if the TSR for the period from November 5, 2014 to November 4, 2017 was greater than 15%. The portion of the total bonus pool payable to individual participants was based on allocations established by the Committee. Participants must have remained employed by the Company through November 4, 2017 unless a participant’s earlier departure from employment was due to death, disability, termination without cause or a change in control transaction. During the year ended December 31, 2017, the TSR did not exceed the minimum target requirement of 15% and the Cash Bonus Program expired without payment. The Company accounted for the Cash Bonus Program under the liability method in accordance with ASC 718. Because vesting of the bonus pool was dependent upon the attainment of a VWAP of $18.37 or higher over the twenty trading days ended November 4, 2017, the Cash Bonus Program was considered to be subject to a “market condition” for the purposes of ASC 718. ASC 718 required the impact of the market condition to be considered when estimating the fair value of the bonus pool. As a result, the Monte Carlo simulation model was applied and the fair value was revalued at each reporting period. As of December 31, 2016, the estimated fair value was $4.8 million. During November 2017, the Cash Bonus Program expired without payout as the VWAP was not achieved. No amounts were accrued as of December 31, 2017 for the Cash Bonus Program. For the year ended December 31, 2017, the Company recorded a reduction in the expense of $3.5 million to the consolidated statement of comprehensive loss as a result of the valuation of the Cash Bonus Program. The most significant assumptions used when assessing the valuation of the Cash Bonus Program were as follows: For the Years Ended December 31, 2016 2015 Valuation date stock price $ 16.18 $ 21.67 Expected volatility 74.7 % 74.8 % Risk-free rate 0.78 % 1.00 % Share-Based Compensation Expense The following table summarizes share-based compensation expense included in the Company’s consolidated statements of comprehensive (loss) income for the years ended December 31, 2017, 2016 and 2015 (in thousands): For the Years Ended December 31, 2017 2016 2015 Share-based compensation expense: Cost of goods sold $ 2,469 $ 26 $ — Research and development 9,263 9,413 6,590 Selling, general and administrative 109,821 104,705 79,196 Total share-based compensation expense $ 121,553 $ 114,144 $ 85,786 During the year ended December 31, 2016, and prior to the adoption of ASU No. 2016-09, no material income tax benefit was recognized relating to share-based compensation expense and no tax benefits were realized from exercised stock options and vested restricted stock units, due to the Company’s net loss position. After the adoption of ASU No. 2016-09, during the year ended December 31, 2017, the Company recognized $2.8 million of tax detriment related to share-based compensation resulting from the current share prices in effect at the time of the exercise of stock options and vesting of restricted stock units. In addition, during the year ended December 31, 2017, $16.4 million of deferred tax assets related to previously recognized share-based compensation expense related to PSUs was charged to income tax expense. As of December 31, 2017, the Company estimates that pre-tax unrecognized compensation expense of $124.9 million for all unvested share-based awards, including stock options, restricted stock units and PSUs, will be recognized through the fourth quarter of 2021. The Company expects to satisfy the exercise of stock options and future distribution of shares for restricted stock units and PSUs by issuing new ordinary shares which have been reserved under the 2014 EIP.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 22 – INCOME TAXES The Company’s (loss) income before benefit for income taxes by jurisdiction for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands): For the Years Ended December 31, 2017 2016 2015 Ireland $ (16,956 ) $ (27,955 ) $ (10,746 ) United States (271,102 ) (165,476 ) (198,442 ) Other foreign (225,217 ) (34,654 ) 76,476 Loss before benefit for income taxes $ (513,275 ) $ (228,085 ) $ (132,712 ) The components of the benefit for income taxes were as follows for the years ended December 31, 2017, 2016 and 2015 (in thousands): For the Years Ended December 31, 2017 2016 2015 Current provision Ireland $ 2,922 $ 1,187 $ 1,924 U.S. - Federal and State 12,085 10,491 6,355 Other foreign 831 679 328 Total current provision 15,838 12,357 8,607 Deferred (benefit) provision Ireland $ (6,294 ) $ (2,054 ) $ (5,623 ) U.S. - Federal and State (120,111 ) (69,073 ) (175,228 ) Other foreign 7,818 (2,481 ) — Total deferred benefit (118,587 ) (73,608 ) (180,851 ) Total benefit for income taxes $ (102,749 ) $ (61,251 ) $ (172,244 ) Total benefit for income taxes was $102.7 million, $61.3 million and $172.2 million for the years ended December 31, 2017, 2016 and 2015, respectively. The current tax provision of $15.8 million for the year ended December 31, 2017 was primarily attributable to U.S. state income tax liabilities and U.S. federal alternative minimum tax liability. The deferred tax benefit of $118.6 million recognized during the year ended December 31, 2017, was primarily due to a provisional $74.9 million net benefit recorded following the enactment of the Tax Act, which net benefit included a $134.2 million tax benefit from the revaluation of the Company’s U.S. net deferred tax liability based on the new U.S. federal tax rate of 21 percent, partially offset by the write-off of a $59.2 million deferred tax asset related to the Company’s U.S. interest expense carryforwards and the U.S. deferred tax benefit incurred on U.S. pre-tax losses. A reconciliation between the Irish income tax statutory rate to the Company’s effective tax rate for 2017, 2016 and 2015 is as follows (in thousands): For the Years Ended December 31, 2017 2016 2015 Irish income tax at statutory rate (12.5%) $ (64,159 ) $ (28,510 ) $ (16,586 ) Foreign tax rate differential (9,806 ) (1,893 ) (30,348 ) Impact of the Tax Act on deferred taxes (134,182 ) — — Write-off of U.S. deferred tax asset related to interest expense carryforwards due to the Tax Act 59,243 — — Notional interest deduction (27,020 ) (35,075 ) (22,848 ) Non-deductible in-process research and development costs 51,148 — — Share-based compensation 26,811 7,125 3,776 Transaction costs 341 3,447 3,109 Disallowed interest 2,990 2,620 2,139 Disqualified compensation expense 1,305 2,555 3,949 Uncertain tax positions 4,976 2,837 3,012 Tax charges on intragroup profit (8,888 ) 2,154 (9,955 ) U.S. state income taxes 214 8,579 1,002 Change in U.S. state effective tax rate (2,329 ) (17,246 ) (9,061 ) Change in valuation allowances (1,378 ) (6,117 ) (106,834 ) U.S. federal and state tax credits (3,608 ) (3,613 ) — Interest expense on convertible debt inducements — — (1,218 ) Book loss on debt extinguishment — — 6,396 Other, net 1,593 1,886 1,223 Benefit for income taxes $ (102,749 ) $ (61,251 ) $ (172,244 ) Effective income tax rate 20.0 % 26.9 % 129.8 % The overall effective income tax rate for 2017 of 20.0% was a higher benefit rate than the Irish statutory rate of 12.5% primarily due to a provisional $74.9 million net benefit recorded following the enactment of the Tax Act, which net benefit included a $134.2 million tax benefit from the revaluation of the Company’s U.S. net deferred tax liability based on the new U.S. federal tax rate of 21 percent, partially offset by the write-off of a $59.2 million deferred tax asset related to the Company’s U.S. interest expense carryforwards. The higher 2017 benefit rate was also attributable to losses incurred in higher tax rate jurisdictions, the benefit realized on the notional interest deduction of $27.0 million, tax charges on intragroup profits of $8.9 million, U.S. federal and state tax credits of $3.6 million and $2.3 million due to a decrease in the U.S. state effective tax rate. These benefits to income taxes are partially offset by non-deductible IPR&D expenses of $51.1 million recorded in connection with the acquisition of River Vision, non-deductible share-based compensation expenses of $26.8 million, including the write-off of $16.4 million of deferred tax assets related to previously recognized share-based compensation expense related to PSUs that expired unvested in December 2017, and an increase in uncertain tax positions of $5.0 million. The overall effective income tax rate for 2016 of 26.9% was a higher benefit rate than the Irish statutory rate of 12.5% primarily due to the benefit realized on the notional interest deduction, the benefit realized from a change in U.S. state effective tax rate, and changes in valuation allowances. These benefits to income taxes were partially offset by an increase in share-based compensation not deductible for tax purposes and an increase in U.S. state income taxes. The overall effective income tax rate for 2015 of 129.8% was a higher benefit rate than the Irish statutory rate of 12.5% primarily due to the release of valuation allowances in the United States following the acquisition of Hyperion in 2015, the benefit realized on the foreign rate differential and the benefit realized on the notional interest deduction. The decrease in the effective income tax rate in 2017 compared to that in 2016 was primarily due to non-deductible IPR&D expenses of $51.1 million recorded in connection with the acquisition of River Vision, an increase in non-deductible share-based compensation of $19.7 million primarily due to the write-off of $16.4 million of deferred tax assets related to previously recognized share-based compensation expense related to PSUs that expired unvested in December 2017, a $14.9 million decrease in benefit from the change in U.S. state effective tax rate, an $11.0 million decrease in the tax charges of intragroup profit, an $8.1 million decrease in the benefit realized on the notional interest deduction and a $4.7 million decrease in the changes in valuation allowances, partially offset by the provisional $74.9 million net impact of the Tax Act on deferred taxes. The decrease in the effective income tax rate in 2016 compared to 2015 was primarily due to the one-time benefit recognized in 2015 for the release in valuation allowance. The Company accounts for income taxes based upon an asset and liability approach. Deferred tax assets and liabilities represent the future tax consequences of the differences between the financial statement carrying amounts of assets and liabilities versus the tax basis of assets and liabilities. Under this method, deferred tax assets are recognized for future deductible temporary differences and operating loss and tax credit carryforwards. Deferred tax liabilities are recognized for future taxable temporary differences. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The impact of tax rate changes on deferred tax assets and liabilities is recognized in the period in which the change is enacted. The tax effects of the temporary differences, tax credits and net operating losses that give rise to significant portions of deferred tax assets and liabilities, before jurisdictional netting, are as follows (in thousands): As of December 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 65,650 $ 99,004 Capital loss carryforwards 2,796 4,631 Alternative minimum tax credit 13,972 5,922 U.S. federal and state credits 35,465 48,758 Accrued compensation 46,420 65,733 Accruals and reserves 11,089 20,179 Contingent royalties 33,436 68,628 Intercompany interest — 54,703 Other 2,259 — Total deferred tax assets 211,087 367,558 Valuation allowance (25,650 ) (32,532 ) Deferred tax assets, net of valuation allowance $ 185,437 $ 335,026 Deferred tax liabilities: Inventories $ 570 $ 13,077 Debt discount 23,372 23,050 Intangible assets 315,970 593,057 Other — 1,499 Total deferred tax liabilities 339,912 630,683 Net deferred income tax liability $ 154,475 $ 295,657 The Tax Act was enacted in December 2017. On December 22, 2017, the SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the date of enactment for companies to complete the accounting under ASC 740, Income Taxes However, the Company has made reasonable estimates of the effects on its income tax provision with respect to certain items, primarily the revaluation of its existing U.S. deferred tax balances and the write-off of its U.S. deferred tax assets resulting from interest expense carryforwards under Section 163(j) of the Internal Revenue Code. In other cases, the Company has not been able to make reasonable estimates and continues to account for those items based on its existing accounting under the provisions of the tax laws that were in effect prior to enactment. The Company recognized a net income tax benefit of $74.9 million for the year ended December 31, 2017, associated with the items it could reasonably estimate. This benefit reflects the revaluation of its U.S. net deferred tax liability based on the U.S. federal tax rate of 21 percent, partially offset by the write-off of the deferred tax asset related to its U.S. interest expense carryforwards. The Company is still analyzing the Tax Act and refining its calculations and the results of this analysis could potentially impact the provisional amounts recorded in 2017 and would be reflected in the 2018 income tax provision. No provision has been made for income taxes on undistributed earnings of subsidiaries because it is the Company’s intention to indefinitely reinvest outside of Ireland undistributed earnings of its subsidiaries. In the event of the distribution of those earnings to Ireland in the form of dividends, a sale of the subsidiaries, or certain other transactions, the Company may be liable for income taxes in Ireland. The unremitted earnings of the Company as of December 31, 2017, were $339.2 million, and the Company estimates that it would incur no additional income tax on unremitted earnings were they to be remitted to Ireland. As of December 31, 2017, the Company had net operating loss carryforwards of approximately $114.4 million for U.S. federal, $307.4 million for various U.S. states and $149.3 million for non-U.S. losses. These net operating losses include net operating losses acquired in the acquisition of River Vision during the second quarter of 2017 and are available to reduce future taxable income, if any, in the jurisdiction in which the net operating losses have been generated. Net operating loss carryforwards for U.S. federal income tax purposes that were generated prior to January 1, 2018, have a twenty-year carryforward life and the earliest layers will begin to expire in 2020. Under the Tax Act, U.S. federal net operating losses incurred in 2018 and in future years may be carried forward indefinitely, but the deductibility of such net operating losses is limited. U.S. state net operating losses started to expire in 2016 for the earliest net operating loss layers. It is uncertain if and to what extent various U.S. states will conform to the Tax Act. Net operating loss carryovers in Switzerland have a seven-year carryforward life and started to expire in 2016 due to lack of sufficient taxable income to fully absorb the available carryover loss. Irish net operating losses may be carried forward indefinitely and therefore have no expiration. Utilization of the U.S. net operating loss carryforwards may be subject to annual limitations as prescribed by federal and state statutory provisions. The imposition of the annual limitations may result in a portion of the net operating loss carryforwards expiring unused. Utilization of certain net operating loss and tax credit carryforwards in the United States is subject to an annual limitation due to ownership change limitations provided by Sections 382 and 383 of the Internal Revenue Code. The Company is limited under the annual limitation of $7.7 million from the year 2018 until 2028 on certain net operating losses generated before an August 2, 2012 ownership change. We continue to carry forward the annual limitation related to Hyperion of $50.0 million resulting from the last ownership change in 2014 as well as the annual limitation related to Raptor of $0.2 million from the year 2018 until 2028 for the ownership change which occurred in 2009. Further, the net operating losses acquired with River Vision are subject to an annual limitation of $12.5 million from 2018 through 2020. The U.S. federal net operating loss carryforward limitation is cumulative such that any use of the carryforwards below the limitation in a particular tax year will result in a corresponding increase in the limitation for the subsequent tax year. At December 31, 2017, the Company had $56.6 million and $6.2 million of U.S. federal and state income tax credits, respectively, to reduce future tax liabilities. These tax credits include the tax credits acquired in the acquisition of River Vision. The federal income tax credits consisted primarily of orphan drug credits, research and development credits and alternative minimum tax credits. The U.S. state income tax credits consisted primarily of California research and development credits and the Illinois Economic Development for a Growing Economy (“EDGE”) tax credits. Both the U.S. federal orphan drug credits and research and development credits have a twenty-year carryforward life. The U.S. federal orphan drug credits and the U.S. federal research and development credits will both begin to expire in 2030. The U.S. federal alternative minimum tax credits and California research and development credits have indefinite lives and therefore are not subject to expiration. The EDGE credits have a five-year carryforward life following the year of generation and will begin to expire in 2019. As the Company’s share price was lower than $31.58 for the twenty trading days ended December 23, 2017, a portion of outstanding PSUs expired unvested and $16.4 million of deferred tax assets related to previously recognized share-based compensation expense related to the expired PSUs was written off to income tax expense. Additionally, in relation to the remaining outstanding PSUs, if our share price is lower than $32.70 and $33.86 for the twenty trading days ending March 22, 2018 and June 22, 2018, respectively, approximately $9.3 million and $8.4 million, respectively, of deferred tax assets at December 31, 2017, related to previously recognized share-based compensation expense related to these PSUs will be charged to income tax expense. A reconciliation of the beginning and ending amounts of valuation allowances for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands): Valuation allowances at December 31, 2014 $ (111,555 ) Increase for 2015 activity (37,569 ) Release of valuation allowances 117,814 Valuation allowances at December 31, 2015 $ (31,310 ) Increase for 2016 activity (14,636 ) Release of valuation allowances 15,056 Additions to valuation allowances due to acquisitions (1,642 ) Valuation allowances at December 31, 2016 $ (32,532 ) Increase for 2017 activity (6,835 ) Release of valuation allowances 5,313 Decreases to valuation allowances due to divestiture 8,404 Valuation allowances at December 31, 2017 $ (25,650 ) Deferred tax valuation allowances decreased by $6.9 million during the year ended December 31, 2017, increased by $1.2 million during the year ended December 31, 2016 and decreased by $80.2 million during the year ended December 31, 2015. For the year ended December 31, 2017, the decrease in valuation allowances resulted primarily from the Chiesi divestiture and the release of valuation allowances related to expired net operating losses in certain jurisdictions, partially offset by the increase resulting from current year activity. The Company is required to recognize the financial statement effects of a tax position when it is more likely than not, based on the technical merits, that the position will be sustained upon examination. The Company accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken, or are expected to be taken, on an income tax return. The changes in the Company's uncertain income tax positions for the years ended December 31, 2017, 2016 and 2015, excluding interest and penalties, consisted of the following (in thousands): For the Years Ended December 31, 2017 2016 2015 Beginning balance – uncertain tax positions $ 17,747 $ 9,812 $ 775 Tax positions in the year: Additions 2,451 471 2,604 Acquired uncertain tax positions — 5,362 6,433 Tax positions related to prior years: Additions 4,145 2,102 — Settlements and lapses (939 ) — — Ending balance – uncertain tax positions $ 23,404 $ 17,747 $ 9,812 For the year ended December 31, 2017, the increase in uncertain tax positions primarily resulted from the additional federal orphan drug credits generated during the year and the uncertain tax position resulting from certain state nexus exposures. In the Company’s consolidated balance sheet, uncertain tax positions of $6.4 million were included in other long-term liabilities and an additional $17.0 million was offset against deferred tax assets. At December 31, 2017, penalties of $0.2 million and interest of $1.3 million are included in the balance of the uncertain tax positions and penalties of $0.1 million and interest of $0.6 million were included in the balance of uncertain tax positions at December 31, 2016. The Company classifies interest and penalties with respect to income tax liabilities as a component of income tax expense. The Company assessed that its liability for uncertain tax positions will not significantly change within the next twelve months. If these uncertain tax positions are released, the impact on the Company’s tax provision would be a benefit of $24.9 million, including interest and penalties. The Company files income tax returns in Ireland, in the United States for federal and various states, as well as in certain other jurisdictions. At December 31, 2017, all open tax years in U.S. federal and certain state jurisdictions date back to 2006 due to the taxing authorities’ ability to adjust operating loss carryforwards. In Ireland, the statute of limitations expires five years from the end of the tax year or four years from the time a tax return is filed, whichever is later. Therefore the earliest year open to examination is 2013 with the lapse of statute occurring in 2018. No changes in settled tax years have occurred to date. On December 29, 2017, the Company received a letter from the U.S. Internal Revenue Service for commencement of a federal income tax examination for the tax year ended December 31, 2015. As of the filing of this Annual Report on Form 10-K, the Company does not currently anticipate material changes from the originally filed U.S. federal tax return for the 2015 year.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	NOTE 23 – EMPLOYEE BENEFIT PLANS The Company sponsors a defined contribution 401(k) retirement savings plan covering all of its U.S. employees, whereby an eligible employee may elect to contribute a portion of his or her salary on a pre-tax basis, subject to applicable federal limitations. The Company is not required to make any discretionary matching of employee contributions. The Company makes a matching contribution equal to 100% of each employee’s elective contribution to the plan of up to 3% of the employee’s eligible pay, and 50% for the next 2% of the employee’s eligible pay. The full amount of this employer contribution is immediately vested in the plan. For the years ended December 31, 2017, 2016 and 2015, the Company recorded defined contribution expense of $4.9 million, $2.7 million and $2.1 million, respectively. The Company’s wholly owned Swiss subsidiary sponsors a defined benefit savings plan covering all of its employees in Switzerland. The Company’s wholly owned German subsidiary sponsors a defined contribution plans for its employees in Germany. For the years ended December 31, 2017, 2016 and 2015, the Company recognized immaterial expenses under these plans. The Company’s wholly owned Irish subsidiary sponsors a defined contribution plan covering all of its employees in Ireland. For the years ended December 31, 2017, 2016 and 2015, the Company recognized expenses of $0.4 million, $0.4 million and $0.2 million, respectively, under this plan. The Company has a non-qualified deferred compensation plan for executives, which was established in April 2015. The deferred compensation plan obligations are payable in cash upon retirement, termination of employment and/or certain other times in a lump-sum distribution or in installments, as elected by the participant in accordance with the plan. As of December 31, 2017 and 2016 $3.1 million, respectively, $6.5 million and $3.1 million December 31, 2017 and 2016, respectively

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information (Unaudited)	NOTE 24 – SELECTED QUARTERLY FINANCIAL INFORMATION (UNAUDITED) The following table provides a summary of selected financial results of operations by quarter for the years ended December 31, 2017 and 2016 (in thousands, except per share data): 2017 First Second Third Fourth Net sales $ 220,859 $ 289,507 $ 271,646 $ 274,219 Gross profit 81,743 159,357 146,129 122,727 Operating loss (105,383 ) (185,667 ) (25,751 ) (75,568 ) Net loss (90,570 ) (209,536 ) (63,971 ) (46,449 ) Net loss per ordinary share - basic $ (0.56 ) $ (1.29 ) $ (0.39 ) $ (0.28 ) Net loss per ordinary share - diluted (0.56 ) (1.29 ) (0.39 ) (0.28 ) 2016 First Second Third Fourth Net sales $ 204,690 $ 257,378 $ 208,702 $ 310,350 Gross profit 127,457 176,252 123,541 160,598 Operating (loss) income (27,204 ) 31,467 (21,322 ) (130,108 ) Net (loss) income (45,406 ) 14,984 (5,870 ) (130,542 ) Net (loss) income per ordinary share - basic $ (0.28 ) $ 0.09 $ (0.04 ) $ (0.81 ) Net (loss) income per ordinary share - diluted (0.28 ) 0.09 (0.04 ) (0.81 )

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation And Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS For Each of the Three Fiscal Years Ended December 31, 2017, 2016 and 2015: Balance at Additions charged to Deductions Balance at Valuation and Qualifying Accounts beginning Acquisitions costs and from end of (in thousands) of period /(Divestitures) expenses reserves period Year ended December 31, 2017: Allowance for discounts and returns 21,916 - 125,851 (100,671 ) 47,096 Year ended December 31, 2016: Allowance for discounts and returns 14,964 1,234 81,089 (75,371 ) 21,916 Year ended December 31, 2015: Allowance for discounts and returns 4,483 236 55,702 (45,457 ) 14,964

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States of America (“GAAP”). Certain reclassifications have been made to prior-period financial statements to conform to the 2017 presentation. Beginning in the first quarter of 2017, the Company modified its presentation of certain operating expenses. Previously, the Company presented “general and administrative” expenses as one line item in its consolidated statement of comprehensive income (loss), and “selling and marketing” expenses as another. For the year ended December 31, 2017 and prior-period comparisons, the Company now combines these two line items into one line item, titled “selling, general and administrative” expenses.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Segment Information	Segment Information The Company has determined that it operates in one researching, developing and commercializing innovative medicines that address unmet treatment needs
Use of Estimates	U se of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Foreign Currency Translation and Transactions	Foreign Currency Translation and Transactions The reporting currency of the Company and its subsidiaries is the U.S. dollar. The U.S. dollar is the functional currency for the Company’s Ireland and U.S.-based businesses and the majority of its subsidiaries. The Company has foreign subsidiaries that have the Euro and the Canadian Dollar as their functional currency. Foreign currency-denominated assets and liabilities of these subsidiaries are translated into U.S. dollars based on exchange rates prevailing at the end of the period, revenues and expenses are translated at average exchange rates prevailing during the corresponding period, and shareholders’ equity accounts are translated at historical exchange rates as of the date of any equity transaction. The effects of foreign exchange gains and losses arising from the translation of assets and liabilities of those entities where the functional currency is not the U.S. dollar are included as a component of accumulated other comprehensive (loss) income. Gains and losses resulting from foreign currency transactions are reflected within the Company’s results of operations.
Revenue Recognition	Revenue Recognition Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the price is fixed or determinable; and collectability is reasonably assured. Some of the Company’s agreements contain multiple elements and in accordance with these agreements, the Company may be eligible for upfront license fees, marketing or commercial milestones and payment for medicine deliveries. Revenue From Medicine Deliveries Revenue from medicine deliveries comprises substantially all of the Company’s gross sales. The Company recognizes revenue from the sale of its medicines when delivery has occurred, title has transferred, the selling price is fixed or determinable, collectability is reasonably assured and the Company has no further performance obligations. In addition, revenue is only recognized when the right of return no longer exists (which is the earlier of the medicine being dispensed through patient prescriptions or the expiration of the right of return) or when medicine returns can be reasonably estimated. Due to the Company’s ability to reasonably estimate and determine allowances for co-pay and other patient assistance, medicine returns, rebates and discounts based on its own internal data for DUEXIS and RAYOS or data relating to prior sales of its acquired medicines which was received in connection with the acquisition of those medicines, the Company recognizes revenue at the point of sale to wholesale pharmaceutical distributors and pharmacies for all currently distributed medicines. Revenue From Upfront License Fees The Company recognizes revenues from the receipt of non-refundable, upfront license fees. In situations where the licensee is able to obtain stand-alone value from the license and no further performance obligations exist on the Company’s part, revenues are recognized on the earlier of when payments are received or collection is reasonably assured. Where continuing involvement by the Company is required in the form of technology transfer, medicine manufacturing or technical support, revenues are deferred and recognized over the term of the agreement. Revenue From Milestone Receipts Milestone payments are recognized as revenue based on achievement of the associated milestones, as defined in the relevant agreements. Revenue from a milestone achievement is recognized when earned, as evidenced by acknowledgment from the Company’s partner, provided that (1) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement, (2) the milestone represents the culmination of an earnings process and (3) the milestone payment is non-refundable. If any of these criteria are not met, revenue from the milestone achievement is recognized over the remaining minimum period of the Company’s performance obligations under the agreement.
Contractual Allowances	Medicine Sales Discounts and Allowances The Company records allowances for medicine returns, rebates and discounts at the time of sale to wholesale pharmaceutical distributors and pharmacies. The Company is required to make significant judgments and estimates in determining some of these allowances. If actual results differ from its estimates, the Company will be required to make adjustments to these allowances in the future. Medicine returns and discounts are included in “accounts receivable” on the consolidated balance sheet. Accrued rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Commercial Rebates The Company participates in certain commercial rebate programs. Under these rebate programs, the Company pays a rebate to the commercial entity or third-party administrator of the program. The Company accrues estimated rebates based on contract prices, estimated percentages of medicine sold to qualified patients and estimated levels of inventory in the distribution channel and records the rebate as a reduction of revenue. Accrued commercial rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Distribution Service Fees The Company includes distribution service fees paid to its wholesalers for distribution and inventory management services as a reduction to revenue. The Company accrues estimated distribution fees based on contractually determined amounts, typically as a percentage of revenue. Accrued distribution service fees are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Patient Access Programs The Company offers discount card and other programs such as its HorizonCares program to patients under which the patient receives a discount on his or her prescription. In certain circumstances when a patient’s prescription is rejected by a managed care vendor, the Company will pay for the full cost of the prescription. The Company reimburses pharmacies for this discount through third-party vendors. The Company reduces gross sales by the amount of actual co-pay and other patient assistance in the period based on the invoices received. The Company also records an accrual to reduce gross sales for estimated co-pay and other patient assistance on units sold to distributors that have not yet been prescribed/dispensed to a patient. The estimate is based on contract prices, estimated percentages of medicine that will be prescribed to qualified patients, average assistance paid based on reporting from the third-party vendors and estimated levels of inventory in the distribution channel. Accrued co-pay and other patient assistance fees are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Patient assistance programs include both co-pay assistance and fully bought down prescriptions. Sales Returns Consistent with industry practice, the Company maintains a return policy that allows customers to return medicine within a specified period prior to and subsequent to the medicine expiration date. Generally, medicine may be returned for a period beginning six months prior to its expiration date and up to one year after its expiration date. The right of return expires on the earlier of one year after the medicine expiration date or the time that the medicine is dispensed to the patient. The majority of medicine returns result from medicine dating, which falls within the range set by the Company’s policy, and are settled through the issuance of a credit to the customer. The estimate of the provision for returns is based upon the Company’s historical experience with actual returns, which is applied to the level of sales for the period that corresponds to the period during which the customer may return medicines. This period is known to the Company based on the shelf life of medicines at the time of shipment. The Company records sales returns as an allowance against accounts receivable and a reduction of revenue. Prompt Pay Discounts As an incentive for prompt payment, the Company offers a 2% cash discount to customers. The Company expects that all customers will comply with the contractual terms to earn the discount. The Company records the discount as an allowance against accounts receivable and a reduction of revenue. Government Rebates The Company participates in certain federal government rebate programs, such as Medicare and Medicaid. The Company accrues estimated rebates based on percentages of medicine sold to qualified patients, estimated rebate percentages and estimated levels of inventory in the distribution channel that will be sold to qualified patients and records the rebates as a reduction of revenue. Accrued government rebates are included in “accrued trade discounts and rebates” on the consolidated balance sheet. Government Chargebacks The Company provides discounts to federal government qualified entities with whom the Company has contracted. These federal entities purchase medicines from the wholesale pharmaceutical distributors at a discounted price, and the wholesale pharmaceutical distributors then charge back to the Company the difference between the current retail price and the contracted price that the federal entities paid for the medicines. The Company accrues estimated chargebacks based on contract prices and sell-through sales data obtained from third-party information and records the chargeback as a reduction of revenue. Accrued government chargebacks are included in “accrued trade discounts and rebates” on the consolidated balance sheet.
Bad Debt Expense	Bad Debt Expense The Company’s medicines are sold to wholesale pharmaceutical distributors and pharmacies. The Company monitors its accounts receivable balances to determine the impact, if any, of such factors as changes in customer concentration, credit risk and the realizability of its accounts receivable, and records a bad debt reserve when applicable.
Inventories	Inventories Inventories are stated at the lower of cost or market value, using the first-in, first-out convention. Inventories consist of raw materials, work-in-process and finished goods. The Company has entered into manufacturing and supply agreements for the manufacture or purchase of raw materials and production supplies. The Company’s inventories include the direct purchase cost of materials and supplies and manufacturing overhead costs. The Company reviews its inventory balance and purchase obligations to assess if it has obsolete or excess inventory and records a charge to “cost of goods sold” when applicable. Inventories acquired in business combinations are recorded at their estimated fair values. “Step-up” represents the write-up of inventory from the lower of cost or market value (the historical book value as previously recorded on the acquired company’s balance sheet) to fair market value at the acquisition date. Inventory step-up expense is recorded in the consolidated statement of comprehensive (loss) income based on actual sales, or usage, using the first-in, first-out convention. Inventories exclude medicine sample inventory, which is included in other current assets and is expensed as a component of “selling, general and administrative” expense when shipped to sales representatives.
Cost of Goods Sold	Cost of Goods Sold The Company recognizes cost of goods sold in connection with its sales of each of its distributed medicines. Cost of goods sold includes all costs directly related to the acquisition of the Company’s medicines from its third-party manufacturers, including freight charges and other direct expenses such as insurance and supply chain costs. Cost of goods sold also includes amortization of intellectual property as described in the intangible assets accounting policy below, inventory step-up expense, drug substance harmonization costs, share-based compensation, charges relating to discontinuation of clinical trials, royalty payments to third parties, royalty accretion expense, changes in estimates associated with the contingent royalty liability as described in the accrued contingent royalty accounting policy below and loss on inventory purchase commitments.
Pre-clinical Studies and Clinical Trial Accruals	Pre-clinical Studies and Clinical Trial Accruals The Company’s pre-clinical studies and clinical trials have historically been conducted by third-party contract research organizations and other vendors. Pre-clinical study and clinical trial expenses are based on the services received from these contract research organizations and vendors. Payments depend on factors such as the milestones accomplished, successful enrollment of certain numbers of patients and site initiation. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual accordingly.
Net (Loss) Income Per Share	Net (Loss) Income Per Share Basic net (loss) income per share is computed by dividing net (loss) income by the weighted-average number of ordinary shares outstanding during the period. Diluted earnings per share (“EPS”) reflects the potential dilution beyond shares for basic EPS that could occur if securities or other contracts to issue ordinary shares were exercised, converted into ordinary shares, or resulted in the issuance of ordinary shares that would have shared in the Company’s earnings.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments, readily convertible to cash, that mature within three months or less from date of purchase to be cash equivalents .
Restricted Cash	Restricted Cash Restricted cash consists primarily of balances in interest-bearing money market accounts required by a vendor for the Company’s sponsored employee business credit card program and collateral for a letter of credit.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, approximate their fair values due to their short maturities.
Business Combinations	Business Combinations The Company accounts for business combinations in accordance with the guidance in Accounting Standards Codification Topic 805 , Business Combinations
Provision for Income Taxes	Provision for Income Taxes The Company accounts for income taxes based upon an asset and liability approach. Deferred tax assets and liabilities represent the future tax consequences of the differences between the financial statement carrying amounts of assets and liabilities versus the tax basis of assets and liabilities. Under this method, deferred tax assets are recognized for deductible temporary differences, and operating loss and tax credit carryforwards. Deferred tax liabilities are recognized for taxable temporary differences. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The impact of tax rate changes on deferred tax assets and liabilities is recognized in the year that the change is enacted. The Company also accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or are expected to be taken on an income tax return. Deferred tax assets and deferred tax liabilities are netted by jurisdiction on the Company’s consolidated balance sheets. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) which provides guidance on accounting for the tax effects of the U.S. H.R. 1, “An Act to provide for reconciliation pursuant to titles II and V of the concurrent resolution on the budget for fiscal year 2018”, informally titled the Tax Cuts and Jobs Act (“the Tax Act”). SAB 118 provides a measurement period that should not extend beyond one year from the date of enactment for companies to complete the accounting under ASC Topic 740, Income Taxes However, the Company has made reasonable estimates of the effects on its income tax provision with respect to certain items, primarily the revaluation of its existing U.S. deferred tax balances and the write-off of its U.S. deferred tax assets resulting from interest expense carryforwards under Section 163(j) of the Internal Revenue Code. In other cases, the Company has not been able to make reasonable estimates and continues to account for those items based on its existing accounting under the provisions of the tax laws that were in effect prior to enactment of the Tax Act.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost less accumulated depreciation. Depreciation is recognized using the straight-line method over the estimated useful lives of the related assets for financial reporting purposes and an accelerated method for income tax reporting purposes. Upon retirement or sale of an asset, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations. Repair and maintenance costs are charged to expenses as incurred and improvements are capitalized. Leasehold improvements are amortized on a straight-line basis over the term of the applicable lease, or the useful life of the assets, whichever is shorter. Depreciation and amortization periods for the Company’s property and equipment are as follows: Machinery and equipment 5 to 7 years Furniture and fixtures 3 to 5 years Computer equipment 3 years Software 3 years Trade show equipment 3 years The Company capitalizes software development costs associated with internal use software, including external direct costs of materials and services and payroll costs for employees devoting time to a software project. Costs incurred during the preliminary project stage, as well as costs for maintenance and training, are expensed as incurred. Software includes internal-use software acquired and modified to meet the Company’s internal requirements. Amortization commences when the software is ready for its intended use.
Intangible Assets	Intangible Assets Definite-lived intangible assets are amortized over their estimated useful lives. The Company reviews its intangible assets when events or circumstances may indicate that the carrying value of these assets exceeds their fair value. The Company measures fair value based on the estimated future discounted cash flows associated with these assets in addition to other assumptions and projections that the Company deems to be reasonable and supportable. The estimated useful lives, from the date of acquisition, for all identified intangible assets that are subject to amortization are between five and thirteen years. The Company determined that no impairment of its definite-lived intangible assets existed as of December 31, 2017. Indefinite-lived intangible assets consist of capitalized in-process research and development (“IPR&D”). IPR&D assets represent capitalized incomplete research projects that the Company acquired through business combinations. Such assets are initially measured at their acquisition date fair values and are tested for impairment, until completion or abandonment of research and development efforts associated with the projects. An IPR&D asset is considered abandoned when research and development efforts associated with the asset have ceased, and there are no plans to sell or license the asset or derive value from the asset. At that point, the asset is considered to be impaired and is written off. Upon successful completion of each project, the Company will make a determination about the then remaining useful life of the intangible asset and begin amortization. The Company tests its indefinite-lived intangible assets, including IPR&D assets, for impairment annually during the fourth quarter and more frequently if events or changes in circumstances indicate that it is more likely than not that the asset is impaired. Following an impairment charge recorded in the fourth quarter of 2016, the Company had no indefinite-lived intangible assets as of December 31, 2017 and 2016. See Note 8 for further details of the impairment charge.
Goodwill	Goodwill Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value of the identifiable net assets acquired. Goodwill is not amortized but is tested for impairment at least annually at the reporting unit level or more frequently if events or changes in circumstances indicate that the asset might be impaired. Impairment loss, if any, is recognized based on a comparison of the fair value of the asset to its carrying value, without consideration of any recoverability. The Company tests goodwill for impairment annually during the fourth quarter and whenever indicators of impairment exist by first assessing qualitative factors to determine whether it is more likely than not that the fair value is less than its carrying amount. If the Company concludes it is more likely than not that the fair value of a reporting unit is less than its carrying amount, a quantitative impairment test is performed. If the Company concludes that goodwill is impaired, it will record an impairment charge in its consolidated statement of comprehensive (loss) income. Based upon the Company’s most recent annual impairment test performed in the fourth quarter of 2017, the Company concluded goodwill was not impaired.
Research and Development Expenses	Research and Development Expenses Research and development expenses include, but are not limited to, payroll and other personnel expenses, consultant expenses, expenses incurred under agreements with contract research organizations to conduct clinical trials, expenses incurred to manufacture clinical trial materials and acquired in-process research and development assets recorded to research and development expense. Research and development expenses were $225.0 million, $60.7 million and $41.9 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Advertising Expenses	Advertising Expenses We expense the costs of advertising as incurred. Advertising expenses were $19.2 million, $14.4 million and $6.1 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Deferred Financing Costs	Deferred Financing Costs Costs incurred in connection with debt financings have been capitalized to “Long-term debt, net, net of current” and “Exchangeable notes, net” in the Company’s consolidated balance sheets as deferred financing costs, and are charged to interest expense using the effective interest method over the terms of the related debt agreements. These costs include document preparation costs, commissions, fees and expenses of investment bankers and underwriters, and accounting and legal fees.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that may potentially subject the Company to significant concentrations of credit risk consist of cash and cash equivalents. The Company’s cash and cash equivalents are invested primarily in money market funds and bank deposits in the United States, Bermuda, Ireland, Switzerland, Luxembourg, Germany, the United Kingdom and Canada that management believes are creditworthy. At times, deposits in these banks may exceed the amount of insurance provided on such deposits. To date, the Company has not experienced any losses on its investments of cash and cash equivalents. The purchase cost of ACTIMMUNE under a contract with Boehringer Ingelheim RCV GmbH & Co. KG (“Boehringer Ingelheim”) as well as sales contracts relating to LODOTRA and QUINSAIR, and sales of RAVICTI and PROCYSBI outside the United States, are principally denominated in Euros or the Canadian dollar and are subject to foreign currency risk. The Company also incurs certain operating expenses in currencies other than the U.S. dollar in relation to its operations and foreign subsidiaries in Ireland, Switzerland, Germany and Canada. The Company does not currently utilize and has not in the past utilized any foreign currency hedging strategies to mitigate the effect of its foreign currency exchange rate risk. Historically, the Company’s accounts receivable balances have been highly concentrated with a select number of customers, consisting primarily of large wholesale pharmaceutical distributors who, in turn, sell the medicines to pharmacies, hospitals and other customers. As of December 31, 2017 and 2016, the Company’s top three customers accounted for approximately 79% and 78%, respectively, of the Company’s total outstanding accounts receivable balances. The Company depends on single-source suppliers and manufacturers for certain of its medicines, medicine candidates and their active pharmaceutical ingredients.
Comprehensive (Loss) Income	Comprehensive (Loss) Income Comprehensive (loss) income is composed of net (loss) income and other comprehensive (loss) income (“OCI”). OCI includes certain changes in shareholders’ equity that are excluded from net (loss) income, which consist of foreign currency translation adjustments and pension remeasurements. The Company reports the effect of significant reclassifications out of accumulated OCI on the respective line items in net income if the amount being reclassified is required under GAAP to be reclassified in its entirety to net income. For other amounts that are not required under GAAP to be reclassified in their entirety to net income in the same reporting period, the Company cross-references other disclosures required under GAAP that provide additional detail about those amounts.
Share-Based Compensation	Share-Based Compensation The Company accounts for employee share-based compensation by measuring and recognizing compensation expense for all share-based payments based on estimated grant date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over each awardee’s requisite service period, which is generally the vesting period. The Company adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting
Accrued Contingent Royalties	Accrued Contingent Royalties The Company’s accrued contingent royalties consist of the contingent royalty obligations assumed by the Company related to the Company’s acquisitions of rights to certain of its medicines. At the time of each acquisition, the Company assigned an estimated fair value to its contingent liability for royalties. The estimated royalty liability is based on anticipated revenue streams utilizing the income approach under the discounted cash flow method. The estimated liability for royalties is increased or decreased over time to reflect the change in its present value and accretion expense is recorded as part of cost of goods sold. The Company evaluates the adequacy of the estimated contingent royalty liability at least annually in the fourth quarter, or whenever events or changes in circumstances indicate that an evaluation of the estimate is necessary. As part of its evaluation, the Company adjusts the carrying value of the liability to the present value of the revised estimated cash flows using the original discount rate. Any adjustment to the liability is recorded as an increase or reduction in cost of goods sold. The royalty liability is included in current and long-term accrued royalties on the consolidated balance sheets.
Contingencies	Contingencies From time to time, the Company may become involved in claims and other legal matters arising in the ordinary course of business. The Company records accruals for loss contingencies to the extent that it concludes that it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. Legal fees and other expenses related to litigation are expensed as incurred and included in “selling, general and administrative” expenses.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, the Company adopts new accounting pronouncements issued by the Financial Accounting Standards Board (“FASB”) or other standard-setting bodies. Effective January 1, 2017, the Company elected to early adopt ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business Effective January 1, 2017, the Company adopted ASU No. 2016-09. The update requires excess tax benefits and tax deficiencies, which arise due to differences between the measure of compensation expense and the amount deductible for tax purposes, to be recorded directly through earnings as a component of income tax expense. Previously, these differences were generally recorded in additional paid-in capital and thus had no impact on net income. The change in treatment of excess tax benefits and tax deficiencies also impacts the computation of diluted earnings per share, and the cash flows associated with those items are classified as operating activities on the consolidated statements of cash flows. Additionally, ASU No. 2016-09 permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated, as allowed under previous standards, or recognized when they occur. As a result of the adoption, $7.2 million of excess tax benefits that had not previously been recognized, as the related tax deduction had not reduced current taxes payable, were recorded on a modified retrospective basis through a cumulative effect adjustment to its accumulated deficit as of January 1, 2017. During the year ended December 31, 2017, the Company recognized an excess tax deficiency in earnings of $2.8 million. The Company elected not to change its policy on accounting for forfeitures and continues to estimate a requisite forfeiture rate. Additional amendments to the accounting for income taxes and minimum statutory withholding requirements had no impact on the Company’s results of operations and related disclosures. In May 2014, the FASB issued ASU Revenue from Contracts with Customers , Revenue From Contracts With Customers, , Revenue Recognition. In October 2016, the FASB issued ASU No. Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting , Compensation- Stock Compensation. In February 2017, the FASB issued ASU No. 2017-05, (“ Subtopic 610-20 , Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Topic 220), (“ASU No. 2018-02”), which permits a company to reclassify the income tax effects of the Tax Act on items within other comprehensive income (“OCI”) to retained earnings. ASU No. 2018-02 requires certain new disclosures, some of which are applicable for all companies and is effective for fiscal years beginning after December 15, 2018, and interim periods during those fiscal years. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment on the Company’s consolidated financial statements and related disclosures. Other recent authoritative guidance issued by the FASB (including technical corrections to the Accounting Standards Codification), the American Institute of Certified Public Accountants, and the Securities and Exchange Commission did not, or are not expected to, have a material impact on the Company’s consolidated financial statements and related disclosures.

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Depreciation and Amortization Periods for Property and Equipment	Depreciation and amortization periods for the Company’s property and equipment are as follows: Machinery and equipment 5 to 7 years Furniture and fixtures 3 to 5 years Computer equipment 3 years Software 3 years Trade show equipment 3 years

Net (Loss) Income per Share (Ta

Net (Loss) Income per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Basic and Diluted Net (Loss) Income per Share	The following table presents basic net (loss) income per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except share and per share data): For the Years Ended December 31, 2017 2016 2015 Basic earnings per share calculation: Net (loss) income $ (410,526 ) $ (166,834 ) $ 39,532 Weighted average of ordinary shares outstanding 163,122,663 160,699,543 148,788,020 Basic net (loss) income per share $ (2.52 ) $ (1.04 ) $ 0.27 The following table presents diluted net (loss) income per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except share and per share data): For the Years Ended December 31, 2017 2016 2015 Diluted earnings per share calculation: Net (loss) income $ (410,526 ) $ (166,834 ) $ 39,532 Weighted average of ordinary shares outstanding 163,122,663 160,699,543 155,923,251 Diluted net (loss) income per share $ (2.52 ) $ (1.04 ) $ 0.25
Schedule of Outstanding Securities Excluded from Computation of Diluted Net Income (Loss) per Ordinary Share	The outstanding securities listed in the table below were excluded from the computation of diluted (loss) income per ordinary share for the years ended December 31, 2017, 2016 and 2015 due to being anti-dilutive: For the Years Ended December 31, 2017 2016 2015 Stock options 12,887,595 7,515,297 2,853,821 Restricted stock units 1,095,768 492,030 817,168 Performance stock units 2,742,301 5,247,987 1,074 Employee stock purchase plan 63,445 56,805 1,046,275 Warrants 388,841 1,123,737 2,416,894 17,177,950 14,435,856 7,135,232

Acquisitions, Divestitures an36

Acquisitions, Divestitures and Other Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Consolidated Pro Forma Financial Information	Additionally, the following table sets forth unaudited financial information and has been compiled from historical financial statements and other information, but is not necessarily indicative of the results that actually would have been achieved had the transactions occurred on the dates indicated or that may be achieved in the future (in thousands, except per share data): For the Year Ended December 31, 2016 2015 As reported Pro forma adjustments Pro forma As reported Pro forma adjustments Pro forma Net sales $ 981,120 $ 109,298 $ 1,090,418 $ 757,044 $ 200,611 $ 957,655 Net (loss) income (166,834 ) (201,765 ) (368,599 ) 39,532 (127,801 ) (88,269 ) Basic net (loss) income per share $ (1.04 ) $ (1.26 ) $ (2.30 ) $ 0.27 $ (0.86 ) $ (0.59 ) Diluted net (loss) income per share (1.04 ) (1.26 ) (2.30 ) 0.25 (0.86 ) (0.59 )
Chiesi Divestiture [Member]
Gain on Divestiture	The gain on divestiture was determined as follows (in thousands): For the Year Ended December 31, 2017 Cash proceeds $ 72,462 Add reimbursement of royalties 27,101 Less net assets sold: Developed technology (47,261 ) Goodwill (16,285 ) Other (24,482 ) Transaction and other costs (5,268 ) Gain on divestiture $ 6,267
Raptor Pharmaceutical Corp [Member]
Total Consideration for Acquisition	The total consideration for the acquisition was approximately $860.8 million, including cash acquired of $24.9 million and $56.0 million paid to settle Raptor’s outstanding debt, and was composed of the following (in thousands): Cash $ 841,494 Net settlements on the exercise of stock options and restricted stock units 19,268 Total consideration $ 860,762
Fair Values Assigned to Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary fair values assigned to the assets acquired and the liabilities assumed by the Company, along with the resulting goodwill before and after the measurement period adjustments (in thousands): (Liabilities assumed) and assets acquired: Preliminary Adjustment Final Accounts payable and accrued expenses $ (28,345 ) $ (240 ) $ (28,585 ) Accrued trade discounts and rebates (6,377 ) 1,350 (5,027 ) Deferred tax liabilities (237,166 ) 1,743 (235,423 ) Contingent and accrued royalties (104,705 ) (104,705 ) Other non-current liability (25,500 ) (25,500 ) Cash and cash equivalents 24,897 24,897 Restricted cash 1,350 1,350 Accounts receivable, net 17,767 17,767 Inventories 74,463 74,463 Prepaid expenses and other current assets 4,194 4,194 Property and equipment 3,373 3,373 Developed technology 946,000 946,000 Other non-current assets 1,765 1,765 Goodwill 189,046 (2,853 ) 186,193 Fair value of consideration paid $ 860,762 $ — $ 860,762
Crealta Holdings LLC [Member]
Total Consideration for Acquisition	The total consideration for the acquisition was approximately $539.7 million, including cash acquired of $24.9 million and $70.9 million paid to settle Crealta’s outstanding debt, and was composed of the following (in thousands): Before Adjustments After Cash $ 536,181 $ 25 $ 536,206 Net settlements on the exercise of stock options and restricted units 3,526 — 3,526 Total consideration $ 539,707 $ 25 $ 539,732
Fair Values Assigned to Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary fair values assigned to the assets acquired and the liabilities assumed by the Company along with the resulting goodwill before and after the measurement period adjustments (in thousands): (Liabilities assumed) and assets acquired: Preliminary Adjustment Final Accounts payable and accrued expenses $ (4,543 ) $ — $ (4,543 ) Accrued trade discounts and rebates (1,424 ) — (1,424 ) Deferred tax liabilities (20,835 ) 694 (20,141 ) Other non-current liabilities (6,900 ) — (6,900 ) Contingent royalty liabilities (51,300 ) — (51,300 ) Cash and cash equivalents 24,893 — 24,893 Accounts receivable 10,014 — 10,014 Inventories 169,054 (19,691 ) 149,363 Prepaid expenses and other current assets 1,382 — 1,382 Developed technology 417,300 10,900 428,200 Other non-current assets 275 — 275 Goodwill 1,791 8,122 9,913 Fair value of consideration paid $ 539,707 $ 25 $ 539,732

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Components of Inventories	The components of inventories as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Raw materials $ 4,553 $ 10,233 Work-in-process 27,589 85,022 Finished goods 29,513 79,533 Inventories, net $ 61,655 $ 174,788

Prepaid Expenses and Other Cu38

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Medicine samples inventory $ 11,415 $ 10,192 Rabbi trust assets 6,490 3,073 Other prepaid expenses and other current assets 25,497 36,354 Prepaid expenses and other current assets $ 43,402 $ 49,619

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Software $ 14,956 $ 10,876 Leasehold improvements 9,415 9,184 Machinery and equipment 4,819 4,566 Computer equipment 2,235 3,069 Other 2,508 2,664 33,933 30,359 Less accumulated depreciation (13,672 ) (8,319 ) Construction in process 144 1,444 Property and equipment, net $ 20,405 $ 23,484

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Gross Carrying Amount of Goodwill	The gross carrying amount of goodwill as of December 31, 2017 was as follows (in thousands): Balance at December 31, 2015 $ 253,811 Goodwill recognized on acquisition of Crealta 9,913 Goodwill recognized on acquisition of Raptor 189,046 Adjustment relating to the acquisition of Hyperion in the prior year (7,191 ) Balance at December 31, 2016 445,579 Goodwill derecognized on Chiesi divestiture (16,285 ) Adjustment relating to the acquisition of Raptor in the prior year (2,853 ) Balance at December 31, 2017 $ 426,441
Amortizable Intangible Assets	As of December 31, 2017 and 2016, amortizable intangible assets consisted of the following (in thousands): As of December 31, 2017 2016 Cost Basis Accumulated Amortization Net Book Value Cost Basis Accumulated Amortization Net Book Value Developed technology $ 3,115,695 $ (671,746 ) $ 2,443,949 $ 3,166,695 $ (399,511 ) $ 2,767,184 Customer relationships 8,100 (2,659 ) 5,441 8,100 (1,849 ) 6,251 Amortizable intangible assets $ 3,123,795 $ (674,405 ) $ 2,449,390 $ 3,174,795 $ (401,360 ) $ 2,773,435
Estimated Future Amortization Expense	As of December 31, 2017, estimated future amortization expense was as follows (in thousands): 2018 $ 274,084 2019 261,092 2020 261,068 2021 253,373 2022 251,551 Thereafter 1,148,222 Total $ 2,449,390

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Accrued Expenses [Member]
Payables And Accruals [Line Items]
Schedule of Accrued Liabilities / Expenses	Accrued expenses as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Payroll-related expenses $ 56,338 $ 66,417 Consulting and professional services 27,542 33,614 Accrued interest 14,127 18,938 Accrued upfront payment related to license agreement 12,000 — Litigation settlement — 32,500 Accrued other 27,827 31,296 Accrued expenses $ 137,834 $ 182,765

Accrued Trade Discounts and R42

Accrued Trade Discounts and Rebates (Tables)	12 Months Ended
	Dec. 31, 2017
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Schedule of Accrued Liabilities / Expenses	Accrued trade discounts and rebates as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 Accrued wholesaler fees and commercial rebates $ 190,215 $ 47,460 Accrued co-pay and other patient assistance 230,533 188,504 Accrued government rebates and chargebacks 81,005 61,592 Accrued trade discounts and rebates $ 501,753 $ 297,556 Invoiced wholesaler fees and commercial rebates, co-pay and other patient assistance, and government rebates and chargebacks in accounts payable 15,042 16,830 Total customer-related accruals and allowances $ 516,795 $ 314,386
Customer-related Accruals and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Schedule of Customer-Related Accruals and Allowances	The following table summarizes changes in the Company’s customer-related accruals and allowances during the years ended December 31, 2017 and 2016 (in thousands): Wholesaler Fees Co-Pay and Government and Commercial Other Patient Rebates and Rebates Assistance Chargebacks Total Balance at December 31, 2015 $ 21,112 $ 114,201 $ 48,456 $ 183,769 Current provisions relating to sales during the year ended December 31, 2016 133,012 1,701,287 278,877 2,113,176 Adjustments relating to prior-year sales 671 — (6,875 ) (6,204 ) Payments relating to sales during the year ended December 31, 2016 (87,147 ) (1,496,240 ) (224,343 ) (1,807,730 ) Payments relating to prior-year sales (20,644 ) (114,201 ) (41,581 ) (176,426 ) Crealta acquisition on January 13, 2016 492 — 932 1,424 Raptor acquisition on October 25, 2016 155 96 6,126 6,377 Balance at December 31, 2016 $ 47,651 $ 205,143 $ 61,592 $ 314,386 Measurement period adjustment — — (1,350 ) (1,350 ) Current provisions relating to sales during the year ended December 31, 2017 635,919 1,907,669 331,559 2,875,147 Adjustments relating to prior-year sales 5,580 (59 ) (4,905 ) 616 Payments relating to sales during the year ended December 31, 2017 (445,621 ) (1,675,344 ) (237,574 ) (2,358,539 ) Payments relating to prior-year sales (53,044 ) (205,084 ) (55,337 ) (313,465 ) Balance at December 31, 2017 $ 190,485 $ 232,325 $ 93,985 $ 516,795

Accrued Royalties (Tables)

Accrued Royalties (Tables)	12 Months Ended
	Dec. 31, 2017
Accrued Royalties [Member]
Schedule of Accrued Liabilities / Expenses	Changes to the liability for royalties for medicines acquired through business combinations during the years ended December 31, 2017 and 2016 consisted of the following (in thousands): Balance as of December 31, 2015 $ 175,219 Accrued royalties - current portion as of December 31, 2015 51,700 Accrued royalties, net of current as of December 31, 2015 123,519 Assumed KRYSTEXXA and MIGERGOT contingent royalty liabilities 51,300 Assumed KRYSTEXXA and MIGERGOT accrued royalties 1,401 Assumed PROCYSBI contingent royalty liabilities 102,000 Assumed PROCYSBI and QUINSAIR accrued royalties 2,705 Remeasurement of royalty liabilities 386 Royalty payments (39,448 ) Accretion expense 40,616 Other royalty expense 95 Balance as of December 31, 2016 334,274 Accrued royalties - current portion as of December 31, 2016 61,981 Accrued royalties, net of current as of December 31, 2016 272,293 Reclassification to other long-term liabilities (5,233 ) Remeasurement of royalty liabilities 21,774 Royalty payments (45,739 ) Accretion expense 51,127 Other royalty expense 310 Balance as of December 31, 2017 356,513 Accrued royalties - current portion as of December 31, 2017 65,328 Accrued royalties, net of current as of December 31, 2017 $ 291,185

Segment and Other Information (

Segment and Other Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Summary of Total Net Revenue by Medicine	The following table presents a summary of total net sales by medicine (in thousands): Year Ended December 31, 2017 2016 2015 RAVICTI $ 193,918 $ 151,532 $ 86,875 PENNSAID 2% 191,050 304,433 147,010 KRYSTEXXA 156,483 91,102 — PROCYSBI 137,740 25,268 — DUEXIS 121,161 173,728 190,357 ACTIMMUNE 110,993 104,624 107,444 VIMOVO 57,666 121,315 166,672 RAYOS 52,125 47,356 40,329 BUPHENYL 20,792 16,879 13,458 MIGERGOT 5,468 4,651 — LODOTRA 5,393 4,193 4,899 QUINSAIR 3,442 1,039 — Litigation settlement — (65,000 ) — Total net sales $ 1,056,231 $ 981,120 $ 757,044
Summary of Total Net Revenues Attributed to Geographic Sources	The following table presents a summary of total net sales by geography (in thousands, except for percentages): Year Ended December 31, Year Ended December 31, 2016 Year Ended December 31, 2015 Amount % of Total Net Sales Amount % of Total Net Sales Amount % of Total Net Sales United States $ 1,026,527 97% $ 964,041 98% $ 744,036 98% Rest of world 29,704 3% 17,079 2% 13,008 2% Total net sales $ 1,056,231 $ 981,120 $ 757,044
Schedule of Gross Sales from Customers Included in Single Operating Segment and All Other Customers as a Group	The following table presents the amount and percentage of gross sales from customers that represented more than 10% of the Company’s gross sales included in its single operating segment, and all other customers as a group (in thousands, except percentages): Year ended December 31, 2017 2016 2015 Amount % of Gross Sales Amount % of Gross Sales Amount % of Gross Sales Customer A $ 1,205,268 30% $ 1,413,774 44% $ 607,771 30% Customer B 1,165,591 29% 667,031 21% 166,661 8% Customer C 567,583 14% 355,920 11% 207,009 10% Other Customers 1,119,397 27% 797,463 24% 1,075,853 52% Gross Sales $ 4,057,839 100% $ 3,234,188 100% $ 2,057,294 100%
Summary of Total Long-Lived Assets by Location	The following table presents total tangible long-lived assets by location (in thousands): As of December 31, 2017 2016 United States $ 17,089 $ 19,542 Other 3,316 3,942 Total long-lived assets (1) $ 20,405 $ 23,484 (1) Long-lived assets consist of property and equipment.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities at Fair Value on Recurring Basis	The following table sets forth the Company’s financial assets and liabilities at fair value on a recurring basis as of December 31, 2017 and 2016 (in thousands): December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Bank time deposits $ — $ 3,000 $ — $ 3,000 Money market funds 687,000 — — 687,000 Other current assets 6,490 — — 6,490 Total assets at fair value $ 693,490 $ 3,000 $ — $ 696,490 Liabilities: Other long-term liabilities (6,490 ) — — (6,490 ) Total liabilities at fair value $ (6,490 ) $ — $ — $ (6,490 ) December 31, 2016 Level 1 Level 2 Level 3 Total Assets: Bank time deposits $ — $ 3,000 $ — $ 3,000 Money market funds 170,000 — — 170,000 Other current assets 3,038 — — 3,038 Total assets at fair value $ 173,038 $ 3,000 $ — $ 176,038 Liabilities: Other long-term liabilities (3,038 ) — — (3,038 ) Total liabilities at fair value $ (3,038 ) $ — $ — $ (3,038 )

Debt Agreements (Tables)

Debt Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Outstanding Debt Balances	The Company’s outstanding debt balances as of December 31, 2017 and 2016 consisted of the following (in thousands): As of December 31, 2017 2016 2017 Term Loan Facility $ 845,750 $ — 2015 Term Loan Facility — 394,000 2016 Incremental Loan Facility — 375,000 2023 Senior Notes 475,000 475,000 2024 Senior Notes 300,000 300,000 Exchangeable Senior Notes 400,000 400,000 Total face value 2,020,750 1,944,000 Debt discount (108,054 ) (126,352 ) Deferred financing fees (11,041 ) (10,155 ) Total long-term debt 1,901,655 1,807,493 Less: current maturities 10,625 7,750 Long-term debt, net of current maturities $ 1,891,030 $ 1,799,743
Schedule of Maturities of Long-term Debt	Scheduled maturities with respect to the Company’s long-term debt are as follows (in thousands): 2018 $ 10,625 2019 8,500 2020 8,500 2021 8,500 2022 406,375 Thereafter 1,578,250 Total $ 2,020,750

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Schedule of Office Space Lease Agreements in Place for Real Properties	The Company has the following office space lease agreements in place for real properties: Location Approximate Square Footage Lease Expiry Date Dublin, Ireland 18,900 November 3, 2029 Lake Forest, Illinois (1) 160,000 March 31, 2024 Novato, California (2) 61,000 August 31, 2021 Deerfield, Illinois (3) 32,300 June 30, 2018 Brisbane, California 20,100 November 30, 2019 Mannheim, Germany 14,300 December 31, 2018 Chicago, Illinois 6,500 December 31, 2018 Other 13,300 March 31, 2018 to May 31, 2020 (1) In connection with the Lake Forest lease, the Company has provided a $2.0 million letter of credit to the landlord, through a commercial bank. (2) During March 2017, the Company vacated an area of the office space in Novato, California. During March and April 2017, the Company entered into sublease arrangements for this space with third parties. (3) During January 2016, the Company vacated the premises in Deerfield, Illinois and began occupying the premises in Lake Forest, Illinois. During April 2017, the Company entered into a sublease arrangement for a portion of this space with a third party. During June 2017, the Company terminated a portion of the lease, resulting in 32,300 square feet remaining.
Schedule of Minimum Future Cash Payments Due under Lease Obligations	As of December 31, 2017, minimum future cash payments due under lease obligations were as follows (in thousands): 2018 $ 7,356 2019 6,659 2020 5,951 2021 5,350 2022 4,092 Thereafter 11,994 Total $ 41,402

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Stock Option Activity	The following table summarizes stock option activity during the year ended December 31, 2017: Weighted Average Weighted Contractual Term Aggregate Average Remaining Intrinsic Value Options Exercise Price (in years) (in thousands) Outstanding as of December 31, 2016 13,627,519 $ 18.17 7.60 $ 35,157 Granted 2,077,215 16.40 Exercised (338,467 ) 6.27 Forfeited (644,752 ) 18.37 Expired (446,199 ) 22.75 Outstanding as of December 31, 2017 14,275,316 18.04 6.97 25,005 Vested and Expected to vest as of December 31, 2017 13,789,210 18.02 6.92 24,960 Exercisable as of December 31, 2017 9,365,306 $ 16.96 6.36 $ 24,158 Stock options typically have a contractual term of ten years from grant date.
Summary of Outstanding Stock Options	The following table summarizes the Company’s outstanding stock options at December 31, 2017: Options Outstanding Options Exercisable Weighted Average Weighted Weighted Average Weighted Remaining Average Remaining Number of options Average Contractual Number Exercise Contractual Exercise Price Ranges outstanding Exercise Price Term (in years) Exercisable Price Term (in years) $2.01 - $4.00 742,582 $ 2.67 5.08 742,582 $ 2.67 5.08 $4.01- $8.00 1,209,543 6.29 4.57 1,199,789 6.28 4.56 $8.01 - $12.00 721,063 9.19 5.41 677,499 9.17 5.34 $12.01 - $17.00 2,552,212 14.12 6.87 1,810,195 14.05 6.11 $17.01 - $22.00 3,252,701 18.11 8.33 1,018,088 18.83 7.51 $22.01 - $28.00 3,412,700 22.31 7.24 2,342,100 22.30 7.23 $28.01 - $36.00 2,384,515 29.47 7.14 1,575,053 29.39 7.01 14,275,316 $ 18.04 6.97 9,365,306 $ 16.96 6.36
Weighted Average Fair Value per Share of Stock Option Awards Granted and Assumptions Used to Value Stock Options	The weighted average fair value per share of stock option awards granted during the years ended December 31, 2017, 2016 and 2015, and assumptions used to value stock options, are as follows: 2017 2016 2015 Dividend yield — — — Risk-free interest rate 1.8%-2.2% 1.3%-2.2% 1.3% - 2.2% Weighted average volatility 49.1 % 73.2 % 77.1 % Expected life (in years) 5.99 6.02 6.07 Weighted average grant date fair value per share of options granted $ 7.96 $ 11.58 $ 16.07
Summary of Restricted Stock Unit Activity	The following table summarizes restricted stock unit activity for the year ended December 31, 2017: Weighted Average Number of Grant-Date Fair Units Value Per Units Outstanding as of December 31, 2016 3,367,871 $ 18.45 Granted 3,732,035 12.44 Vested (1,222,920 ) 16.78 Forfeited (593,136 ) 16.85 Outstanding as of December 31, 2017 5,283,850 $ 14.77 The grant-date fair value of restricted stock units is the closing price of the Company’s shares on the date of grant.
Summary of Performance Stock Unit Awards (PSUs) Activity	The following table summarizes performance stock unit awards (“PSUs”) activity for the year ended December 31, 2017: Weighted Recorded Average Weighted Grant-Date Average Average Number Fair Value Illiquidity Fair Value of Units Per Unit Discount Per Unit Outstanding as of December 31, 2016 12,045,656 Vested and issued (25,000 ) $ 12.36 0.0 % $ 13.30 Expired (1) (3,927,440 ) 14.82 14.9 % 12.60 Forfeited (238,336 ) 10.86 7.5 % 10.04 Outstanding as of December 31, 2017 7,854,880 (1) During the year ended December 31, 2017, the first of three tranches of the Company’s outstanding PSUs expired due to failure to meet the Company’s minimum total compounded annual shareholder rate of return (“TSR”) requirement.
Summary of Vesting Tranches	All PSUs outstanding as of December 31, 2017 were granted in 2015 and 2016 and may vest if the Company’s TSR over two performance measurement periods summarized below equals or exceeds a minimum of 15%. Beginning of Length of Percent of Performance Performance Total PSU Measurement End of Performance Measurement Vesting Tranche Award Period Measurement Period Period (Years) Tranche Two 33.3 % March 23, 2015 March 22, 2018 3.00 Tranche Three 33.3 % March 23, 2015 June 22, 2018 3.25 These outstanding PSUs may vest in amounts ranging from 25% to 100% based on the achievement of the following TSR over the two performance periods: TSR Achieved Vesting 15% 25 % 30% 50 % 45% 75 % 60% 100 %
Summary of Significant Valuation Assumptions	The Company accounts for the PSUs as equity-settled awards in accordance with ASC 718. Because the value of the PSUs is dependent upon the attainment of a level of TSR, it requires the impact of the market condition to be considered when estimating the fair value of the PSUs. As a result, the Monte Carlo model is applied and the most significant valuation assumptions used include: For the Years Ended December 31, 2017 2016 2015 Valuation date stock price N/A $ 17.72 - $21.07 $ 16.81 - $35.06 Expected volatility N/A 76.8% - 77.6% 64.6% - 72.3% Risk-free rate N/A 1.0% - 1.2% 1.0% - 1.1%
Summary of Average Estimated Fair Value of PSU	The average estimated fair value of each outstanding PSU is as follows (allocated between groupings based on grant-date classification): Recorded Weighted Weighted Average Fair Average Average Number Value Per Illiquidity Fair Value of Units Unit Discount Per Unit Executive committee members 6,014,437 $ 15.16 17.1 % $ 12.57 Non-executive committee members 1,840,443 13.71 7.3 % 12.71 7,854,880 $ 14.82 14.9 % $ 12.60
Summary of Share-Based Compensation Expense	The following table summarizes share-based compensation expense included in the Company’s consolidated statements of comprehensive (loss) income for the years ended December 31, 2017, 2016 and 2015 (in thousands): For the Years Ended December 31, 2017 2016 2015 Share-based compensation expense: Cost of goods sold $ 2,469 $ 26 $ — Research and development 9,263 9,413 6,590 Selling, general and administrative 109,821 104,705 79,196 Total share-based compensation expense $ 121,553 $ 114,144 $ 85,786
Cash Long-Term Incentive Program [Member]
Summary of Significant Valuation Assumptions	The most significant assumptions used when assessing the valuation of the Cash Bonus Program were as follows: For the Years Ended December 31, 2016 2015 Valuation date stock price $ 16.18 $ 21.67 Expected volatility 74.7 % 74.8 % Risk-free rate 0.78 % 1.00 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Company's of (Loss) Income Before Benefit for Income Taxes	The Company’s (loss) income before benefit for income taxes by jurisdiction for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands): For the Years Ended December 31, 2017 2016 2015 Ireland $ (16,956 ) $ (27,955 ) $ (10,746 ) United States (271,102 ) (165,476 ) (198,442 ) Other foreign (225,217 ) (34,654 ) 76,476 Loss before benefit for income taxes $ (513,275 ) $ (228,085 ) $ (132,712 )
Components of benefit for Income Taxes	The components of the benefit for income taxes were as follows for the years ended December 31, 2017, 2016 and 2015 (in thousands): For the Years Ended December 31, 2017 2016 2015 Current provision Ireland $ 2,922 $ 1,187 $ 1,924 U.S. - Federal and State 12,085 10,491 6,355 Other foreign 831 679 328 Total current provision 15,838 12,357 8,607 Deferred (benefit) provision Ireland $ (6,294 ) $ (2,054 ) $ (5,623 ) U.S. - Federal and State (120,111 ) (69,073 ) (175,228 ) Other foreign 7,818 (2,481 ) — Total deferred benefit (118,587 ) (73,608 ) (180,851 ) Total benefit for income taxes $ (102,749 ) $ (61,251 ) $ (172,244 )
Reconciliation Between Irish Rate and U.S Federal Statutory Income Tax Rate	A reconciliation between the Irish income tax statutory rate to the Company’s effective tax rate for 2017, 2016 and 2015 is as follows (in thousands): For the Years Ended December 31, 2017 2016 2015 Irish income tax at statutory rate (12.5%) $ (64,159 ) $ (28,510 ) $ (16,586 ) Foreign tax rate differential (9,806 ) (1,893 ) (30,348 ) Impact of the Tax Act on deferred taxes (134,182 ) — — Write-off of U.S. deferred tax asset related to interest expense carryforwards due to the Tax Act 59,243 — — Notional interest deduction (27,020 ) (35,075 ) (22,848 ) Non-deductible in-process research and development costs 51,148 — — Share-based compensation 26,811 7,125 3,776 Transaction costs 341 3,447 3,109 Disallowed interest 2,990 2,620 2,139 Disqualified compensation expense 1,305 2,555 3,949 Uncertain tax positions 4,976 2,837 3,012 Tax charges on intragroup profit (8,888 ) 2,154 (9,955 ) U.S. state income taxes 214 8,579 1,002 Change in U.S. state effective tax rate (2,329 ) (17,246 ) (9,061 ) Change in valuation allowances (1,378 ) (6,117 ) (106,834 ) U.S. federal and state tax credits (3,608 ) (3,613 ) — Interest expense on convertible debt inducements — — (1,218 ) Book loss on debt extinguishment — — 6,396 Other, net 1,593 1,886 1,223 Benefit for income taxes $ (102,749 ) $ (61,251 ) $ (172,244 ) Effective income tax rate 20.0 % 26.9 % 129.8 %
Deferred Tax Assets and Liabilities	The tax effects of the temporary differences, tax credits and net operating losses that give rise to significant portions of deferred tax assets and liabilities, before jurisdictional netting, are as follows (in thousands): As of December 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 65,650 $ 99,004 Capital loss carryforwards 2,796 4,631 Alternative minimum tax credit 13,972 5,922 U.S. federal and state credits 35,465 48,758 Accrued compensation 46,420 65,733 Accruals and reserves 11,089 20,179 Contingent royalties 33,436 68,628 Intercompany interest — 54,703 Other 2,259 — Total deferred tax assets 211,087 367,558 Valuation allowance (25,650 ) (32,532 ) Deferred tax assets, net of valuation allowance $ 185,437 $ 335,026 Deferred tax liabilities: Inventories $ 570 $ 13,077 Debt discount 23,372 23,050 Intangible assets 315,970 593,057 Other — 1,499 Total deferred tax liabilities 339,912 630,683 Net deferred income tax liability $ 154,475 $ 295,657
Reconciliation of Beginning and Ending Amounts of Valuation Allowance	A reconciliation of the beginning and ending amounts of valuation allowances for the years ended December 31, 2017, 2016 and 2015 is as follows (in thousands): Valuation allowances at December 31, 2014 $ (111,555 ) Increase for 2015 activity (37,569 ) Release of valuation allowances 117,814 Valuation allowances at December 31, 2015 $ (31,310 ) Increase for 2016 activity (14,636 ) Release of valuation allowances 15,056 Additions to valuation allowances due to acquisitions (1,642 ) Valuation allowances at December 31, 2016 $ (32,532 ) Increase for 2017 activity (6,835 ) Release of valuation allowances 5,313 Decreases to valuation allowances due to divestiture 8,404 Valuation allowances at December 31, 2017 $ (25,650 )
Changes in Uncertain Income Tax Positions	The changes in the Company's uncertain income tax positions for the years ended December 31, 2017, 2016 and 2015, excluding interest and penalties, consisted of the following (in thousands): For the Years Ended December 31, 2017 2016 2015 Beginning balance – uncertain tax positions $ 17,747 $ 9,812 $ 775 Tax positions in the year: Additions 2,451 471 2,604 Acquired uncertain tax positions — 5,362 6,433 Tax positions related to prior years: Additions 4,145 2,102 — Settlements and lapses (939 ) — — Ending balance – uncertain tax positions $ 23,404 $ 17,747 $ 9,812

Selected Quarterly Financial 50

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of Selected Financial Results of Operations	The following table provides a summary of selected financial results of operations by quarter for the years ended December 31, 2017 and 2016 (in thousands, except per share data): 2017 First Second Third Fourth Net sales $ 220,859 $ 289,507 $ 271,646 $ 274,219 Gross profit 81,743 159,357 146,129 122,727 Operating loss (105,383 ) (185,667 ) (25,751 ) (75,568 ) Net loss (90,570 ) (209,536 ) (63,971 ) (46,449 ) Net loss per ordinary share - basic $ (0.56 ) $ (1.29 ) $ (0.39 ) $ (0.28 ) Net loss per ordinary share - diluted (0.56 ) (1.29 ) (0.39 ) (0.28 ) 2016 First Second Third Fourth Net sales $ 204,690 $ 257,378 $ 208,702 $ 310,350 Gross profit 127,457 176,252 123,541 160,598 Operating (loss) income (27,204 ) 31,467 (21,322 ) (130,108 ) Net (loss) income (45,406 ) 14,984 (5,870 ) (130,542 ) Net (loss) income per ordinary share - basic $ (0.28 ) $ 0.09 $ (0.04 ) $ (0.81 ) Net (loss) income per ordinary share - diluted (0.28 ) 0.09 (0.04 ) (0.81 )

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail)	Jun. 30, 2017	Jun. 23, 2017	May 08, 2017	Oct. 25, 2016	Jan. 13, 2016	May 07, 2015
European Subsidiary that Owned Marketing Rights to PROCYSBI and QUINSAIR [Member]
Basis Of Presentation [Line Items]
Business divestiture date		Jun. 23, 2017
Boehringer Ingelheim International GmbH [Member]
Basis Of Presentation [Line Items]
Business acquisition date	Jun. 30, 2017
Hyperion Therapeutics, Inc. [Member]
Basis Of Presentation [Line Items]
Business acquisition date						May 7, 2015
Crealta Holdings LLC [Member]
Basis Of Presentation [Line Items]
Business acquisition date					Jan. 13, 2016
River Vision [Member]
Basis Of Presentation [Line Items]
Business acquisition date			May 8, 2017
Raptor Pharmaceutical Corp [Member]
Basis Of Presentation [Line Items]
Business acquisition date				Oct. 25, 2016

Summary of Significant Accoun52

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017USD ($)SegmentCustomer	Dec. 31, 2016USD ($)Customer	Dec. 31, 2015USD ($)	Jan. 01, 2017USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment | Segment		1
Cash discount to incentive for prompt payment		2.00%
Net income tax benefit		$ 74,900,000
Impairment of definite-lived intangible assets		0
Indefinite-lived intangible assets		0	$ 0
Research and development expenses		224,962,000	60,707,000	$ 41,865,000
Advertising expenses		19,200,000	14,400,000	$ 6,100,000
Cumulative effect adjustment to accumulated deficit		(1,252,329,000)	$ (848,021,000)
ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment to accumulated deficit					$ 7,200,000
Excess tax deficiency		2,800,000
ASU No. 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected deferred revenue reclassified directly to retained earnings upon adoption		11,000,000
ASU No. 2016-16 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment of deferred tax assets directly to retained earnings		$ 9,000,000
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of major customers for accounts receivable | Customer		3	3
Percentage of concentration risk		79.00%	78.00%
Scenario Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
U.S. federal corporate tax rate	21.00%
Restatement Adjustment [Member] | ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment to accumulated deficit					$ 7,200,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents maturity period		3 months
Useful life of intangible assets		13 years
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of intangible assets		5 years

Summary of Significant Accoun53

Summary of Significant Accounting Policies - Depreciation and Amortization Periods for Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Machinery and Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	5 years
Machinery and Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	7 years
Furniture and Fixtures [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	5 years
Computer Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	3 years
Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	3 years
Trade Show Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization	3 years

Net (Loss) Income per Share - B

Net (Loss) Income per Share - Basic and Diluted Net (Loss) Income per Share (Detail) - 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
Basic earnings per share calculation:
Net (loss) income									$ (410,526)	$ (166,834)	$ 39,532
Weighted average of ordinary shares outstanding									163,122,663	160,699,543	148,788,020
Basic net (loss) income per share	$ (0.28)	$ (0.39)	$ (1.29)	$ (0.56)	$ (0.81)	$ (0.04)	$ 0.09	$ (0.28)	$ (2.52)	$ (1.04)	$ 0.27
Diluted earnings per share calculation:
Net (loss) income									$ (410,526)	$ (166,834)	$ 39,532
Weighted average of ordinary shares outstanding									163,122,663	160,699,543	155,923,251
Diluted net (loss) income per share	$ (0.28)	$ (0.39)	$ (1.29)	$ (0.56)	$ (0.81)	$ (0.04)	$ 0.09	$ (0.28)	$ (2.52)	$ (1.04)	$ 0.25

Net (Loss) Income per Share - S

Net (Loss) Income per Share - Schedule of Outstanding Securities Excluded from Computation of Diluted Loss per Ordinary Share (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	17,177,950	14,435,856	7,135,232
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	388,841	1,123,737	2,416,894
Employee Stock Purchase Plans [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	63,445	56,805	1,046,275
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	12,887,595	7,515,297	2,853,821
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	1,095,768	492,030	817,168
Performance Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reconciliation of basic and diluted earnings per share	2,742,301	5,247,987	1,074

Net (Loss) Income per Share - A

Net (Loss) Income per Share - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 13, 2015
Earnings Per Share [Line Items]
Senior notes	$ 1,576,646	$ 1,501,741
Incremental common shares attributable to dilutive effect of conversion of Exchangeable Senior Notes	0	0	0
Exchangeable Senior Notes [Member]
Earnings Per Share [Line Items]
Interest rate	2.50%
Horizon Investment [Member] | Exchangeable Senior Notes [Member]
Earnings Per Share [Line Items]
Senior notes				$ 400,000
Maturity year of debt instrument	2,022	2,022
Interest rate	2.50%	2.50%

Acquisitions, Divestitures an57

Acquisitions, Divestitures and Other Arrangements - Additional Information (Detail) $ / shares in Units, € in Millions

Jun. 30, 2017USD ($)Country$ / €

Jun. 30, 2017EUR (€)Country$ / €

Jun. 23, 2017USD ($)

May 08, 2017USD ($)$ / SFr

Nov. 08, 2016USD ($)

Oct. 25, 2016USD ($)$ / shares

Jan. 13, 2016USD ($)

May 07, 2015

May 31, 2016USD ($)$ / €

May 31, 2016EUR (€)$ / €

Dec. 31, 2017USD ($)€ / $$ / SFr

Sep. 30, 2017USD ($)

Jun. 30, 2017USD ($)Country$ / €

Mar. 31, 2017USD ($)

Dec. 31, 2016USD ($)€ / $

Sep. 30, 2016USD ($)

Jun. 30, 2016USD ($)

Mar. 31, 2016USD ($)

Dec. 31, 2017USD ($)€ / $$ / SFr

Dec. 31, 2017CHF (SFr)

Dec. 31, 2016USD ($)€ / $

Dec. 31, 2016EUR (€)

Dec. 31, 2015USD ($)

Dec. 31, 2017EUR (€)€ / $$ / SFr

Dec. 12, 2017USD ($)

Jun. 27, 2017USD ($)

Business Acquisition [Line Items]

State net operating losses

$ 35,465,000

$ 48,758,000

$ 35,465,000

$ 48,758,000

Senior notes

1,576,646,000

1,501,741,000

$ 1,576,646,000

1,501,741,000

Percentage of estimated cash flows expected to be realized

90.00%

90.00%

Net sales

$ 274,219,000

$ 271,646,000

$ 289,507,000

$ 220,859,000

$ 310,350,000

$ 208,702,000

$ 257,378,000

$ 204,690,000

$ 1,056,231,000

981,120,000

$ 757,044,000

Maximum [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

13 years

13 years

Minimum [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

5 years

5 years

US [Member]

Business Acquisition [Line Items]

Net sales

$ 1,026,527,000

964,041,000

744,036,000

Non-US [Member]

Business Acquisition [Line Items]

Net sales

29,704,000

$ 17,079,000

13,008,000

Chiesi Divestiture [Member]

Business Acquisition [Line Items]

Gain on divestiture of inventory

3,200,000

Chiesi Divestiture [Member] | Disposal Group, Not Discontinued Operations [Member]

Business Acquisition [Line Items]

Sale of subsidiary

$ 72,500,000

$ 72,462,000

Cash divested

$ 3,100,000

2024 Senior Notes [Member]

Business Acquisition [Line Items]

Interest rate

8.75%

8.75%

8.75%

8.75%

ACTIMMUNE Developed Technology [Member]

Business Acquisition [Line Items]

Currency exchange rate | € / $

1.052

1.052

Impairment charge

$ 5,300,000

€ 5

Net sales

$ 110,993,000

104,624,000

107,444,000

PROCYSBI and QUINSAIR [Member] | Chiesi Divestiture [Member]

Business Acquisition [Line Items]

Gain on divestiture of inventory

3,200,000

PROCYSBI and QUINSAIR [Member] | Chiesi Divestiture [Member] | Disposal Group, Not Discontinued Operations [Member]

Business Acquisition [Line Items]

Estimated amount of assets expected to be reimbursed

$ 24,600,000

24,600,000

$ 27,100,000

QUINSAIR Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

3,442,000

1,039,000

PROCYSBI Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

$ 137,740,000

25,268,000

PROCYSBI Developed Technology [Member] | Developed Technology [Member] | US [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

13 years

13 years

PROCYSBI Developed Technology [Member] | Developed Technology [Member] | Non-US [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

9 years

9 years

KRYSTEXXA Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

$ 156,483,000

91,102,000

KRYSTEXXA Developed Technology [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

12 years

12 years

MIGERGOT Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

$ 5,468,000

4,651,000

MIGERGOT Developed Technology [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets estimated useful life

10 years

10 years

RAVICTI [Member]

Business Acquisition [Line Items]

Net sales

$ 193,918,000

151,532,000

86,875,000

BUPHENYL [Member]

Business Acquisition [Line Items]

Net sales

20,792,000

16,879,000

13,458,000

River Vision [Member]

Business Acquisition [Line Items]

Percentage of equity interests acquired

100.00%

Business acquisition agreement date

May 8, 2017

Upfront cash payments

$ 150,300,000

$ 2,000,000

SFr 2,000,000

Cash acquired from acquisition

6,300,000

Federal net operating losses

13,100,000

State net operating losses

2,800,000

Federal tax credits

$ 5,800,000

Business acquisition date

May 8, 2017

Currency exchange rate | $ / SFr

1.0169

1.0263

1.0263

1.0263

Boehringer Ingelheim International GmbH [Member]

Business Acquisition [Line Items]

Upfront cash payments

$ 22,300,000

€ 19.5

$ 5,600,000

€ 5

Business acquisition date

Jun. 30, 2017

Jun. 30, 2017

Number of estimated countries commercializes under trade names | Country

30

30

30

Currency exchange rate | $ / €

1.1406

1.1406

1.1132

1.1132

1.1406

Boehringer Ingelheim International GmbH [Member] | Selling, General and Administrative [Member]

Business Acquisition [Line Items]

Currency exchange rate | € / $

1.1406

1.1406

1.1406

Additional payment to be recorded upon closing

$ 22,300,000

$ 22,300,000

€ 19.5

Raptor Pharmaceutical Corp [Member]

Business Acquisition [Line Items]

Upfront cash payments

$ 841,494,000

Cash acquired from acquisition

$ 24,900,000

Business acquisition date

Oct. 25, 2016

Business acquisition share price | $ / shares

$ 9

Debt instrument, aggregate principal amount

$ 375,000,000

Total consideration

860,762,000

Outstanding debt amount paid

56,000,000

Acquisition related transaction costs

15,700,000

Goodwill, measurement period adjustments

(2,853,000)

Inventory

74,463,000

74,463,000

Preliminary fair value of liability

102,000,000

$ 102,000,000

Income tax rate reconciliation, tax settlement, domestic percent

36.60%

36.60%

Raptor Pharmaceutical Corp [Member] | Step-Up Adjustments [Member]

Business Acquisition [Line Items]

Inventory

67,000,000

Raptor Pharmaceutical Corp [Member] | 2024 Senior Notes [Member]

Business Acquisition [Line Items]

Senior notes

$ 300,000,000

Interest rate

8.75%

Maturity year of debt instrument

2,024

Raptor Pharmaceutical Corp [Member] | PROCYSBI and QUINSAIR [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Inventory step-up expense including gain on divestiture

$ 44,000,000

Inventory step-up expense

40,800,000

22,400,000

Raptor Pharmaceutical Corp [Member] | QUINSAIR Developed Technology [Member]

Business Acquisition [Line Items]

Contingent liability

$ 25,500,000

Payment for milestones in connection with assumed contingent consideration liability

$ 20,000,000

Net sales

1,000,000

Raptor Pharmaceutical Corp [Member] | PROCYSBI Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

25,300,000

Raptor Pharmaceutical Corp [Member] | PROCYSBI Developed Technology [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Present value at discount rate

12.50%

12.50%

Crealta Holdings LLC [Member]

Business Acquisition [Line Items]

Upfront cash payments

$ 536,206,000

Cash acquired from acquisition

$ 24,900,000

Business acquisition date

Jan. 13, 2016

Total consideration

$ 539,732,000

Outstanding debt amount paid

$ 70,900,000

Goodwill, measurement period adjustments

8,100,000

Inventory

$ 149,363,000

149,363,000

Preliminary fair value of liability

51,300,000

$ 51,300,000

Crealta Holdings LLC [Member] | Commercial Supply Agreements [Member]

Business Acquisition [Line Items]

Contingent liability

6,900,000

6,900,000

Crealta Holdings LLC [Member] | Step-Up Adjustments [Member]

Business Acquisition [Line Items]

Inventory

144,300,000

144,300,000

Crealta Holdings LLC [Member] | KRYSTEXXA and MIGERGOT [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Inventory step-up expense

78,300,000

Crealta Holdings LLC [Member] | KRYSTEXXA Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

91,100,000

Crealta Holdings LLC [Member] | KRYSTEXXA Developed Technology [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Inventory step-up expense

$ 78,300,000

Present value at discount rate

27.00%

27.00%

Crealta Holdings LLC [Member] | MIGERGOT Developed Technology [Member]

Business Acquisition [Line Items]

Net sales

4,700,000

Crealta Holdings LLC [Member] | MIGERGOT Developed Technology [Member] | Developed Technology [Member]

Business Acquisition [Line Items]

Present value at discount rate

23.00%

23.00%

Crealta Holdings LLC [Member] | Selling, General and Administrative [Member]

Business Acquisition [Line Items]

Acquisition related transaction costs

3,500,000

1,900,000

Privately-held life-science entity [Member]

Business Acquisition [Line Items]

Payment of option to acquire assets

$ 100,000

Payment to acquire assets

25,000,000

Payment to be made upon attainment of milestones

$ 9,800,000

Privately-held life-science entity [Member] | Other Assets [Member]

Business Acquisition [Line Items]

Initial upfront amount

100,000

$ 100,000

$ 100,000

100,000

Privately-held life-science entity [Member] | Research and Development [Member]

Business Acquisition [Line Items]

Upfront cash payments

1,500,000

1,100,000

MedImmune [Member] | HZN-003 (Formerly MEDI4945) [Member]

Business Acquisition [Line Items]

Upfront cash payment

$ 12,000,000

MedImmune [Member] | HZN-003 (Formerly MEDI4945) [Member] | Maximum [Member]

Business Acquisition [Line Items]

Payment to be made upon attainment of milestones

$ 153,500,000

MedImmune [Member] | Research and Development [Member] | HZN-003 (Formerly MEDI4945) [Member]

Business Acquisition [Line Items]

Upfront cash payment

$ 12,000,000

$ 12,000,000

Hyperion Therapeutics, Inc. [Member]

Business Acquisition [Line Items]

Business acquisition date

May 7, 2015

Goodwill, measurement period adjustments

$ (7,191,000)

Hyperion Therapeutics, Inc. [Member] | RAVICTI [Member]

Business Acquisition [Line Items]

Net sales

86,900,000

Hyperion Therapeutics, Inc. [Member] | BUPHENYL [Member]

Business Acquisition [Line Items]

Net sales

$ 13,500,000

Acquisitions, Divestitures an58

Acquisitions, Divestitures and Other Arrangements - Total Consideration for Acquisition Including Cash Acquired (Detail) - USD ($) $ in Thousands	Oct. 25, 2016	Jan. 13, 2016
Raptor Pharmaceutical Corp [Member]
Business Acquisition [Line Items]
Cash	$ 841,494
Net settlements on the exercise of stock options and restricted stock units	19,268
Total consideration	860,762
Raptor Pharmaceutical Corp [Member] | Before [Member]
Business Acquisition [Line Items]
Total consideration	$ 860,762
Crealta Holdings LLC [Member]
Business Acquisition [Line Items]
Cash		$ 536,206
Net settlements on the exercise of stock options and restricted units		3,526
Total consideration		539,732
Crealta Holdings LLC [Member] | Before [Member]
Business Acquisition [Line Items]
Cash		536,181
Net settlements on the exercise of stock options and restricted units		3,526
Total consideration		539,707
Crealta Holdings LLC [Member] | Adjustments [Member]
Business Acquisition [Line Items]
Cash		25
Total consideration		$ 25

Acquisitions, Divestitures an59

Acquisitions, Divestitures and Other Arrangements - Fair Values Assigned to Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Oct. 25, 2016	Jan. 13, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill			$ 445,579	$ 426,441	$ 253,811
Raptor Pharmaceutical Corp [Member]
Business Acquisition [Line Items]
Accounts payable and accrued expenses				(28,585)
Accrued trade discounts and rebates				(5,027)
Deferred tax liabilities				(235,423)
Contingent and accrued royalties				(104,705)
Other non-current liability				(25,500)
Cash and cash equivalents				24,897
Restricted cash				1,350
Accounts receivable, net				17,767
Inventories				74,463
Prepaid expenses and other current assets				4,194
Property and equipment				3,373
Other non-current assets				1,765
Goodwill			189,100	186,193
Fair value of consideration paid	$ 860,762
Raptor Pharmaceutical Corp [Member] | Preliminary [Member]
Business Acquisition [Line Items]
Accounts payable and accrued expenses	(28,345)
Accrued trade discounts and rebates	(6,377)
Deferred tax liabilities	(237,166)
Contingent and accrued royalties	(104,705)
Other non-current liability	(25,500)
Cash and cash equivalents	24,897
Restricted cash	1,350
Accounts receivable, net	17,767
Inventories	74,463
Prepaid expenses and other current assets	4,194
Property and equipment	3,373
Other non-current assets	1,765
Goodwill	189,046
Fair value of consideration paid	860,762
Raptor Pharmaceutical Corp [Member] | Restatement Adjustment [Member]
Business Acquisition [Line Items]
Accounts payable and accrued expenses				(240)
Accrued trade discounts and rebates				1,350
Deferred tax liabilities				1,743
Goodwill				(2,853)
Raptor Pharmaceutical Corp [Member] | Developed Technology [Member]
Business Acquisition [Line Items]
Intangible assets				$ 946,000
Raptor Pharmaceutical Corp [Member] | Developed Technology [Member] | Preliminary [Member]
Business Acquisition [Line Items]
Intangible assets	$ 946,000
Crealta Holdings LLC [Member]
Business Acquisition [Line Items]
Accounts payable and accrued expenses			(4,543)
Accrued trade discounts and rebates			(1,424)
Deferred tax liabilities			(20,141)
Other non-current liability			(6,900)
Contingent royalty liabilities			(51,300)
Cash and cash equivalents			24,893
Accounts receivable, net			10,014
Inventories			149,363
Prepaid expenses and other current assets			1,382
Other non-current assets			275
Goodwill			9,913
Fair value of consideration paid		$ 539,732
Crealta Holdings LLC [Member] | Preliminary [Member]
Business Acquisition [Line Items]
Accounts payable and accrued expenses		(4,543)
Accrued trade discounts and rebates		(1,424)
Deferred tax liabilities		(20,835)
Other non-current liability		(6,900)
Contingent royalty liabilities		(51,300)
Cash and cash equivalents		24,893
Accounts receivable, net		10,014
Inventories		169,054
Prepaid expenses and other current assets		1,382
Other non-current assets		275
Goodwill		1,791
Fair value of consideration paid		539,707
Crealta Holdings LLC [Member] | Restatement Adjustment [Member]
Business Acquisition [Line Items]
Deferred tax liabilities			694
Inventories			(19,691)
Goodwill			8,122
Fair value of consideration paid			25
Crealta Holdings LLC [Member] | Developed Technology [Member]
Business Acquisition [Line Items]
Intangible assets			428,200
Crealta Holdings LLC [Member] | Developed Technology [Member] | Preliminary [Member]
Business Acquisition [Line Items]
Intangible assets		$ 417,300
Crealta Holdings LLC [Member] | Developed Technology [Member] | Restatement Adjustment [Member]
Business Acquisition [Line Items]
Intangible assets			$ 10,900

Acquisitions, Divestitures an60

Acquisitions, Divestitures and Other Arrangements - Gain on Divestiture (Detail) - Disposal Group, Not Discontinued Operations [Member] - Chiesi Divestiture [Member] - USD ($) $ in Thousands	Jun. 23, 2017	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Cash proceeds	$ 72,500	$ 72,462
Add reimbursement of royalties		27,101
Less net assets sold:
Developed technology		(47,261)
Goodwill		(16,285)
Other		(24,482)
Transaction and other costs		(5,268)
Gain on divestiture		$ 6,267

Acquisitions, Divestitures an61

Acquisitions, Divestitures and Other Arrangements - Consolidated Pro Forma Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Net sales	$ 1,090,418	$ 957,655
Net (loss) income	$ (368,599)	$ (88,269)
Basic net (loss) income per share	$ (2.30)	$ (0.59)
Diluted net (loss) income per share	$ (2.30)	$ (0.59)
Before [Member]
Business Acquisition [Line Items]
Net sales	$ 981,120	$ 757,044
Net (loss) income	$ (166,834)	$ 39,532
Basic net (loss) income per share	$ (1.04)	$ 0.27
Diluted net (loss) income per share	$ (1.04)	$ 0.25
Adjustments [Member]
Business Acquisition [Line Items]
Net sales	$ 109,298	$ 200,611
Net (loss) income	$ (201,765)	$ (127,801)
Basic net (loss) income per share	$ (1.26)	$ (0.86)
Diluted net (loss) income per share	$ (1.26)	$ (0.86)

Inventories - Components of Inv

Inventories - Components of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 4,553	$ 10,233
Work-in-process	27,589	85,022
Finished goods	29,513	79,533
Inventories, net	$ 61,655	$ 174,788

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Inventory [Line Items]
Finished goods	$ 29,513	$ 79,533
Work-in-process	27,589	85,022
Chiesi Divestiture [Member]
Inventory [Line Items]
Gain on divestiture of inventory	3,200
PROCYSBI and QUINSAIR [Member] | Chiesi Divestiture [Member]
Inventory [Line Items]
Gain on divestiture of inventory	3,200
Crealta Holdings LLC [Member] | Developed Technology [Member] | KRYSTEXXA Developed Technology [Member]
Inventory [Line Items]
Finished goods	17,000	27,700
Inventory step-up expense	78,300
Work-in-process		67,600
Raptor Pharmaceutical Corp [Member] | Developed Technology [Member] | PROCYSBI and QUINSAIR [Member]
Inventory [Line Items]
Finished goods		38,100
Inventory step-up expense	$ 40,800	22,400
Work-in-process		$ 5,900

Prepaid Expenses and Other Cu64

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Medicine samples inventory	$ 11,415	$ 10,192
Rabbi trust assets	6,490	3,073
Other prepaid expenses and other current assets	25,497	36,354
Prepaid expenses and other current assets	$ 43,402	$ 49,619

Property and Equipment - Proper

Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 33,933	$ 30,359
Less accumulated depreciation	(13,672)	(8,319)
Property and equipment, net	20,405	23,484
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,956	10,876
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,415	9,184
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,819	4,566
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,235	3,069
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,508	2,664
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 144	$ 1,444

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Depreciation expense	$ 6.6	$ 5	$ 5.4

Goodwill and Intangible Asset67

Goodwill and Intangible Assets - Schedule of Gross Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Beginning balance	$ 445,579	$ 253,811
Ending balance	426,441	445,579
Disposal Group, Not Discontinued Operations [Member] | Chiesi Divestiture [Member]
Goodwill [Line Items]
Goodwill derecognized on Chiesi divestiture	(16,285)
Crealta Holdings LLC [Member]
Goodwill [Line Items]
Beginning balance	9,913
Goodwill recognized on acquisition		9,913
Adjustment relating to the prior year acquisition		8,100
Ending balance		9,913
Raptor Pharmaceutical Corp [Member]
Goodwill [Line Items]
Beginning balance	189,100
Goodwill recognized on acquisition		189,046
Adjustment relating to the prior year acquisition	(2,853)
Ending balance	$ 186,193	189,100
Hyperion Therapeutics, Inc. [Member]
Goodwill [Line Items]
Adjustment relating to the prior year acquisition		$ (7,191)

Goodwill and Intangible Asset68

Goodwill and Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)Project	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 08, 2016USD ($)
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 426,441,000	$ 445,579,000	$ 253,811,000
Indefinite-lived intangible assets	0	0
Amortization expense of developed technology	$ 276,800,000	216,900,000	$ 132,900,000
ACTIMMUNE Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets				$ 66,000,000
Impairment of acquired in-process R&D		66,000,000
Developed Technology [Member] | PROCYSBI Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized intangible asset		946,000,000
Developed Technology [Member] | KRYSTEXXA Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized intangible asset		402,200,000
Developed Technology [Member] | MIGERGOT Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized intangible asset		26,000,000
In-Process Research and Development [Member] | ACTIMMUNE Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Number of projects | Project	1
Raptor Pharmaceutical Corp [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 186,193,000	189,100,000
Goodwill, measurement period adjustments	(2,853,000)
Crealta Holdings LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill		9,913,000
Goodwill, measurement period adjustments		8,100,000
Accumulated goodwill impairment losses	0
Hyperion Therapeutics, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, measurement period adjustments		$ (7,191,000)
Disposal Group, Not Discontinued Operations [Member] | Chiesi Divestiture [Member]
Finite-Lived Intangible Assets [Line Items]
Reduction in goodwill	(16,300,000)
Disposal Group, Not Discontinued Operations [Member] | Chiesi Divestiture [Member] | Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Reduction in net book value	$ 47,300,000

Goodwill and Intangible Asset69

Goodwill and Intangible Assets - Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Cost Basis	$ 3,123,795	$ 3,174,795
Accumulated Amortization	(674,405)	(401,360)
Net Book Value	2,449,390	2,773,435
Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Cost Basis	3,115,695	3,166,695
Accumulated Amortization	(671,746)	(399,511)
Net Book Value	2,443,949	2,767,184
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost Basis	8,100	8,100
Accumulated Amortization	(2,659)	(1,849)
Net Book Value	$ 5,441	$ 6,251

Goodwill and Intangible Asset70

Goodwill and Intangible Assets - Estimated Future Amortization Expense (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
2,018	$ 274,084
2,019	261,092
2,020	261,068
2,021	253,373
2,022	251,551
Thereafter	1,148,222
Net Book Value	$ 2,449,390	$ 2,773,435

Other Assets - Additional Infor

Other Assets - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Jun. 27, 2017
PROCYSBI and QUINSAIR [Member] | Disposal Group, Not Discontinued Operations [Member] | Chiesi Divestiture [Member]
Business Acquisition [Line Items]
Estimated long-term portion of assets expected to be reimbursed	$ 24.6	$ 27.1

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Payroll-related expenses	$ 56,338	$ 66,417
Consulting and professional services	27,542	33,614
Accrued interest	14,127	18,938
Accrued upfront payment related to license agreement	12,000
Litigation settlement		32,500
Accrued other	27,827	31,296
Accrued expenses	$ 137,834	$ 182,765

Accrued Expenses - Additional I

Accrued Expenses - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 12, 2017USD ($)
Schedule Of Accrued Expenses [Line Items]
Accrued litigation settlement		$ 32,500
Accrued other	$ 27,827	31,296
Other long-term liabilities	68,015	46,061
Costs to be incurred to discontinue clinical trial		4,000
Reduction in research and development expenses	1,500
MedImmune [Member] | HZN-003 (Formerly MEDI4945) [Member]
Schedule Of Accrued Expenses [Line Items]
Upfront cash payment			$ 12,000
Research and Development [Member] | MedImmune [Member] | HZN-003 (Formerly MEDI4945) [Member]
Schedule Of Accrued Expenses [Line Items]
Upfront cash payment	12,000
Loss on Inventory Purchase Commitments [Member]
Schedule Of Accrued Expenses [Line Items]
Accrued other	2,100	9,500
Other long-term liabilities	7,800	4,800
Cost to be Incurred in Write-down of Inventory [Member]
Schedule Of Accrued Expenses [Line Items]
Accrued other		4,000
Express Scripts, Inc. [Member]
Schedule Of Accrued Expenses [Line Items]
Accrued litigation settlement		$ 32,500
Litigation settlement number of installment		2
Boehringer Ingelheim [Member] | Cost of Goods Sold [Member]
Schedule Of Accrued Expenses [Line Items]
Recorded loss on non-cancellable and unconditional purchase		$ 14,300
Boehringer Ingelheim [Member] | Loss on Inventory Purchase Commitments [Member] | Cost of Goods Sold [Member]
Schedule Of Accrued Expenses [Line Items]
Recorded additional expense in renegotiated purchase commitments	$ 1,700

Accrued Trade Discounts and R74

Accrued Trade Discounts and Rebates - Schedule of Accrued Trade Discounts and Rebates (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrued Wholesaler Fees And Commercial Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	$ 190,215	$ 47,460
Accrued Co-Pay and Other Patient Assistance [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	230,533	188,504
Accrued Government Rebates and Chargebacks [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	81,005	61,592
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	501,753	297,556
Invoiced Wholesaler Fees and Commercial Rebates, Co pay and Other Patient Assistance, and Government Rebates and Chargebacks in Accounts Payable [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	15,042	16,830
Customer-related Accruals and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	$ 516,795	$ 314,386	$ 183,769

Accrued Trade Discounts and R75

Accrued Trade Discounts and Rebates - Schedule of Customer-Related Accruals and Allowances (Detail) - USD ($) $ in Thousands	Oct. 25, 2016	Jan. 13, 2016	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions				$ 1,642
Wholesaler Fees and Commercial Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance			$ 47,651	21,112
Current provisions relating to sales			635,919	133,012
Adjustments relating to prior-year sales			5,580	671
Payments relating to sales			(445,621)	(87,147)
Payments relating to prior-year sales			(53,044)	(20,644)
Ending Balance			190,485	47,651
Wholesaler Fees and Commercial Rebates [Member] | Crealta Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions		$ 492
Wholesaler Fees and Commercial Rebates [Member] | Raptor Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions	$ 155
Co-Pay and Other Patient Assistance [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance			205,143	114,201
Current provisions relating to sales			1,907,669	1,701,287
Adjustments relating to prior-year sales			(59)
Payments relating to sales			(1,675,344)	(1,496,240)
Payments relating to prior-year sales			(205,084)	(114,201)
Ending Balance			232,325	205,143
Co-Pay and Other Patient Assistance [Member] | Raptor Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions	96
Government Rebates and Chargebacks [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance			61,592	48,456
Measurement period adjustment			(1,350)
Current provisions relating to sales			331,559	278,877
Adjustments relating to prior-year sales			(4,905)	(6,875)
Payments relating to sales			(237,574)	(224,343)
Payments relating to prior-year sales			(55,337)	(41,581)
Ending Balance			93,985	61,592
Government Rebates and Chargebacks [Member] | Crealta Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions		932
Government Rebates and Chargebacks [Member] | Raptor Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions	6,126
Customer-related Accruals and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance			314,386	183,769
Measurement period adjustment			(1,350)
Current provisions relating to sales			2,875,147	2,113,176
Adjustments relating to prior-year sales			616	(6,204)
Payments relating to sales			(2,358,539)	(1,807,730)
Payments relating to prior-year sales			(313,465)	(176,426)
Ending Balance			$ 516,795	$ 314,386
Customer-related Accruals and Allowances [Member] | Crealta Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions		$ 1,424
Customer-related Accruals and Allowances [Member] | Raptor Acquisition [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Acquisitions	$ 6,377

Accrued Royalties - Schedule of

Accrued Royalties - Schedule of Changes in Liability for Royalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Beginning balance	$ 334,274	$ 175,219
Accrued royalties—current portion	65,328	61,981	$ 51,700
Accrued royalties, net of current	291,185	272,293	123,519
Reclassification to other long-term liabilities	(5,233)
Remeasurement of royalty liabilities	21,774	386	21,151
Royalty payments	(45,739)	(39,448)
Accretion expense	51,127	40,616
Other royalty expense	310	95
Ending balance	$ 356,513	334,274	$ 175,219
KRYSTEXXA and MIGERGOT [Member]
Business Acquisition [Line Items]
Assumed contingent royalty liabilities		51,300
Assumed accrued royalties		1,401
PROCYSBI [Member]
Business Acquisition [Line Items]
Assumed contingent royalty liabilities		102,000
PROCYSBI and QUINSAIR [Member]
Business Acquisition [Line Items]
Assumed accrued royalties		$ 2,705

Accrued Royalties - Additional

Accrued Royalties - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Cost of goods sold and selling, general and administrative expenses	$ 64.7
Selling, General and Administrative [Member]
Business Acquisition [Line Items]
Cost of goods sold and selling, general and administrative expenses	0.6
Developed Technology [Member]
Business Acquisition [Line Items]
Reversal of royalty expenses included in cost of goods sold	43.5
Developed Technology [Member] | KRYSTEXXA Developed Technology [Member] | Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Cost of goods sold and selling, general and administrative expenses	40.5
Developed Technology [Member] | RAVICTI [Member] | Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Cost of goods sold and selling, general and administrative expenses	24.2
Developed Technology [Member] | PROCYSBI [Member] | Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Reversal of royalty expenses included in cost of goods sold	23.2
Developed Technology [Member] | ACTIMMUNE Developed Technology [Member] | Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Reversal of royalty expenses included in cost of goods sold	7
Developed Technology [Member] | VIMOVO [Member] | Cost of Goods Sold [Member]
Business Acquisition [Line Items]
Reversal of royalty expenses included in cost of goods sold	$ 11.7

Long-Term Investments - Additio

Long-Term Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Sales proceeds					$ 42,781
Gain (loss) on sale of long-term investments			$ 0	$ 0	$ (29,032)
Depomed, Inc [Member]
Schedule Of Available For Sale Securities [Line Items]
Common stock shares purchased from Depomed		2,250,000
Percentage of outstanding common stock shares purchased from Depomed		3.75%
Cost of shares acquired		$ 71,800
Sales proceeds	$ 42,800
Gain (loss) on sale of long-term investments	$ (29,000)

Segment and Other Information -

Segment and Other Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting Information [Line Items]
Number of operating segment	1
Customer Concentration Risk [Member] | Sales Revenue [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Percentage of concentration risk	10.00%

Segment and Other Information80

Segment and Other Information - Summary of Total Net Sales by Medicine (Detail) - USD ($) $ 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
Segment Reporting Information [Line Items]
Total net sales	$ 274,219	$ 271,646	$ 289,507	$ 220,859	$ 310,350	$ 208,702	$ 257,378	$ 204,690	$ 1,056,231	$ 981,120	$ 757,044
Total net sales										(65,000)
DUEXIS [Member]
Segment Reporting Information [Line Items]
Total net sales									121,161	173,728	190,357
VIMOVO [Member]
Segment Reporting Information [Line Items]
Total net sales									57,666	121,315	166,672
PENNSAID 2% [Member]
Segment Reporting Information [Line Items]
Total net sales									191,050	304,433	147,010
ACTIMMUNE [Member]
Segment Reporting Information [Line Items]
Total net sales									110,993	104,624	107,444
RAVICTI [Member]
Segment Reporting Information [Line Items]
Total net sales									193,918	151,532	86,875
KRYSTEXXA [Member]
Segment Reporting Information [Line Items]
Total net sales									156,483	91,102
RAYOS [Member]
Segment Reporting Information [Line Items]
Total net sales									52,125	47,356	40,329
BUPHENYL [Member]
Segment Reporting Information [Line Items]
Total net sales									20,792	16,879	13,458
PROCYSBI [Member]
Segment Reporting Information [Line Items]
Total net sales									137,740	25,268
LODOTRA [Member]
Segment Reporting Information [Line Items]
Total net sales									5,393	4,193	$ 4,899
MIGERGOT [Member]
Segment Reporting Information [Line Items]
Total net sales									5,468	4,651
QUINSAIR [Member]
Segment Reporting Information [Line Items]
Total net sales									$ 3,442	$ 1,039

Segment and Other Information81

Segment and Other Information - Summary of Total Net Sales Attributed to Geographic Sources (Detail) - USD ($) $ 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
Segment Reporting Information [Line Items]
Net sales	$ 274,219	$ 271,646	$ 289,507	$ 220,859	$ 310,350	$ 208,702	$ 257,378	$ 204,690	$ 1,056,231	$ 981,120	$ 757,044
United States [Member]
Segment Reporting Information [Line Items]
Net sales									$ 1,026,527	$ 964,041	$ 744,036
United States [Member] | Geographic Concentration Risk [Member] | Sales Revenue Net [Member]
Segment Reporting Information [Line Items]
Percentage of concentration risk									97.00%	98.00%	98.00%
Non-US [Member]
Segment Reporting Information [Line Items]
Net sales									$ 29,704	$ 17,079	$ 13,008
Non-US [Member] | Geographic Concentration Risk [Member] | Sales Revenue Net [Member]
Segment Reporting Information [Line Items]
Percentage of concentration risk									3.00%	2.00%	2.00%

Segment and Other Information82

Segment and Other Information - Schedule of Gross Sales from Customers Included in Single Operating Segment and All Other Customers as a Group (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 4,057,839	$ 3,234,188	$ 2,057,294
Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	100.00%	100.00%	100.00%
Customer A [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 1,205,268	$ 1,413,774	$ 607,771
Customer A [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	30.00%	44.00%	30.00%
Customer B [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 1,165,591	$ 667,031	$ 166,661
Customer B [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	29.00%	21.00%	8.00%
Customer C [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 567,583	$ 355,920	$ 207,009
Customer C [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	14.00%	11.00%	10.00%
Other Customers [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 1,119,397	$ 797,463	$ 1,075,853
Other Customers [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	27.00%	24.00%	52.00%

Segment and Other Information83

Segment and Other Information - Summary of Total Long-Lived Assets by Location (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total long-lived assets	[1]	$ 20,405	$ 23,484
United States [Member]
Segment Reporting Information [Line Items]
Total long-lived assets		17,089	19,542
Other [Member]
Segment Reporting Information [Line Items]
Total long-lived assets		$ 3,316	$ 3,942
[1]	Long-lived assets consist of property and equipment.

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Transfers from level 1 to level 2, assets	$ 0		$ 0
Transfers from level 2 to level 1, assets	0		$ 0
Transfers of assets into level 3	0	$ 0
Transfers of assets out of level 3	$ 0	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring Basis [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	$ 696,490	$ 176,038
Total liabilities at fair value	(6,490)	(3,038)
Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	3,000	3,000
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	687,000	170,000
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	6,490	3,038
Other Long-term Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(6,490)	(3,038)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	693,490	173,038
Total liabilities at fair value	(6,490)	(3,038)
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	687,000	170,000
Level 1 [Member] | Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	6,490	3,038
Level 1 [Member] | Other Long-term Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(6,490)	(3,038)
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	3,000	3,000
Level 2 [Member] | Bank Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	$ 3,000	$ 3,000

Debt Agreements - Outstanding D

Debt Agreements - Outstanding Debt Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total face value	$ 2,020,750	$ 1,944,000
Debt discount	(108,054)	(126,352)
Deferred financing fees	(11,041)	(10,155)
Total long-term debt	1,901,655	1,807,493
Less: current maturities	10,625	7,750
Long-term debt, net of current maturities	1,891,030	1,799,743
2017 Term Loan Facility [Member]
Debt Instrument [Line Items]
Total face value	845,750
2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
Total face value		394,000
2016 Incremental Loan Facility [Member]
Debt Instrument [Line Items]
Total face value		375,000
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Total face value	475,000	475,000
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Total face value	300,000	300,000
Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Total face value	$ 400,000	$ 400,000

Debt Agreements - Outstanding87

Debt Agreements - Outstanding Debt Balances (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument	May 1, 2023
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument	Nov. 1, 2024
2017 Term Loan Facility [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument	Mar. 29, 2024
2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument	May 7, 2015
2016 Incremental Loan Facility [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument	Oct. 25, 2016

Debt Agreements - Scheduled Mat

Debt Agreements - Scheduled Maturities of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,018	$ 10,625
2,019	8,500
2,020	8,500
2,021	8,500
2,022	406,375
Thereafter	1,578,250
Total	$ 2,020,750	$ 1,944,000

Debt Agreements - Additional In

Debt Agreements - Additional Information (Detail)	Oct. 23, 2017USD ($)	Mar. 29, 2017USD ($)	Oct. 25, 2016USD ($)	May 07, 2015USD ($)	Apr. 29, 2015USD ($)	Dec. 31, 2017USD ($)d$ / shares	Dec. 31, 2015USD ($)	Dec. 31, 2016USD ($)	Mar. 13, 2015USD ($)
Debt Instrument [Line Items]
Senior notes						$ 1,576,646,000		$ 1,501,741,000
Initial debt discount						$ 108,054,000		$ 126,352,000
Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument						Mar. 15, 2022
Debt instrument, effective interest rate						8.88%
Debt instrument, fair value						$ 372,000,000
Interest rate						2.50%
Redemption price as percentage of aggregate principal amount						100.00%
Debt Instrument, Convertible, Conversion Ratio (in shares per $1,000 principal amount)						34.8979
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares						$ 28.66
Debt instrument convertible minimum percentage						130.00%
Debt instrument number of trading days | d						20
Debt instrument consecutive trading days | d						30
Carrying amount of liability component						$ 268,900,000
Carrying amount of equity component						119,100,000
Initial proceeds from convertible debt instrument						387,200,000	$ 387,181,000
Initial debt discount						$ 131,100,000
Exchangeable Senior Notes [Member] | Conversion Condition One [Member]
Debt Instrument [Line Items]
Debt instrument convertible minimum percentage						130.00%
Debt instrument number of trading days | d						20
Debt instrument consecutive trading days | d						30
Exchangeable Senior Notes [Member] | Conversion Condition Two [Member]
Debt Instrument [Line Items]
Debt instrument number of trading days | d						5
Debt instrument consecutive trading days | d						10
Convertible senior notes, principal payment						$ 1,000
Debt instrument convertible maximum percentage						98.00%
Exchangeable Senior Notes [Member] | Horizon Investment [Member]
Debt Instrument [Line Items]
Senior notes									$ 400,000,000
Interest rate						2.50%		2.50%
Net proceeds from senior notes						$ 387,200,000
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument						May 1, 2023
Debt instrument, effective interest rate						6.68%
Debt instrument, fair value						$ 473,800,000
Interest rate					6.625%	6.63%
Debt instrument redemption description						the 2023 Senior Notes may be redeemed at any time at specified redemption prices, plus accrued and unpaid interest to the redemption date. At any time prior to May 1, 2018, some or all of the 2023 Senior Notes may be redeemed at a price equal to 100% of the aggregate principal amount thereof, plus a make-whole premium and accrued and unpaid interest to the redemption date. Also prior to May 1, 2018, up to 35% of the aggregate principal amount of the 2023 Senior Notes may be redeemed at a redemption price of 106.625% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings. In addition, the 2023 Senior Notes may be redeemed in whole but not in part at a redemption price equal to 100% of the principal amount plus accrued and unpaid interest and additional amounts, if any, to, but excluding, the redemption date, if on the next date on which any amount would be payable in respect of the 2023 Senior Notes, HPI or any guarantor is or would be required to pay additional amounts as a result of certain tax-related events.
2023 Senior Notes [Member] | Prior to May 1, 2018 [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount					106.625%
2023 Senior Notes [Member] | Prior to May 1, 2018, Some or All of Aggregate Principal Amount [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount					100.00%
2023 Senior Notes [Member] | After May 1, 2018, in Whole But Not in Part [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount					100.00%
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument						Nov. 1, 2024
Debt instrument, effective interest rate						9.20%
Debt instrument, fair value						$ 316,500,000
Interest rate			8.75%			8.75%
Debt instrument redemption description						the 2024 Senior Notes may be redeemed at any time at specified redemption prices, plus accrued and unpaid interest to the redemption date. At any time prior to November 1, 2019, some or all of the 2024 Senior Notes may be redeemed at a price equal to 100% of the aggregate principal amount thereof, plus a make-whole premium and accrued and unpaid interest to the redemption date. Also prior to November 1, 2019, up to 35% of the aggregate principal amount of the 2024 Senior Notes may be redeemed at a redemption price of 108.75% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings. In addition, the 2024 Senior Notes may be redeemed in whole but not in part at a redemption price equal to 100% of the principal amount plus accrued and unpaid interest and additional amounts, if any, to, but excluding, the redemption date, if on the next date on which any amount would be payable in respect of the 2024 Senior Notes, the 2024 Issuers or any guarantor is or would be required to pay additional amounts as a result of certain tax-related events.
2024 Senior Notes [Member] | Prior to November 1, 2019 [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount			108.75%
2024 Senior Notes [Member] | Prior to November 1, 2019, Some or All of Aggregate Principal Amount [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount			100.00%
2024 Senior Notes [Member] | After November 1, 2019, in Whole But Not in Part [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount			100.00%
Maximum [Member] | 2023 Senior Notes [Member] | Prior to May 1, 2018 [Member]
Debt Instrument [Line Items]
Redemption amount as percentage of aggregate principal amount					35.00%
Maximum [Member] | 2024 Senior Notes [Member] | Prior to November 1, 2019 [Member]
Debt Instrument [Line Items]
Redemption amount as percentage of aggregate principal amount			35.00%
2017 Term Loan Facility [Member]
Debt Instrument [Line Items]
LIBOR floor rate	1.00%
Interest rate description						The October 2017 Refinancing Loans bear interest, at the Borrowers’ option, at a rate equal to either the London Inter-Bank Offer Rate (“LIBOR”), plus an applicable margin of 3.25% per year (subject to a LIBOR floor of 1.00%), or the adjusted base rate plus 2.25%. The adjusted base rate is defined as the greater of (a) LIBOR (using one-month interest period) plus 1.00%, (b) prime rate, (c) fed funds plus 0.5%, and (d) 2.00%.
Repayment of refinanced loans, amount	$ 845,800,000
Cut off percentage for defining limited liability subsidiaries, portion of capital stock held maximum	65.00%
Proceeds from debt issuances, percentage on excess cash flow	50.00%
Proceeds from debt issuances, reduction percentage on excess cash flow	25.00%
Proceeds from debt issuances, percentage on first lien leverage ratio	0.00%
Principal amount of loan, amortization percentage	1.00%
Credit agreement, description						The Borrowers are required to make mandatory prepayments of loans under the Credit Agreement (without payment of a premium) with (a) net cash proceeds from certain non-ordinary course asset sales (subject to reinvestment rights and other exceptions), (b) casualty proceeds and condemnation awards (subject to reinvestment rights and other exceptions), (c) net cash proceeds from issuances of debt (other than certain permitted debt), and (d) 50% of the Company’s excess cash flow (subject to decrease to 25% or 0% if the Company’s first lien leverage ratio is less than 2.25:1 or 1.75:1, respectively). The October 2017 Refinancing Loans will amortize in equal quarterly installments beginning on December 31, 2017, in an aggregate annual amount equal to 1.00% of the original principal amount of the October 2017 Refinanced Loans (i.e. $850.0 million), with any remaining balance payable on March 29, 2024, the final maturity date of the October 2017 Refinancing Loans.
Debt instrument, aggregate principal amount	$ 850,000,000
Maturity date of debt instrument						Mar. 29, 2024
Debt instrument, variable interest rate						4.75%
Debt instrument, effective interest rate						5.16%
2017 Term Loan Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
First lien leverage ratio	225.00%
2017 Term Loan Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
First lien leverage ratio	175.00%
2017 Term Loan Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt instrument variable rate	3.25%
2017 Term Loan Facility [Member] | Adjusted Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument variable rate	2.25%
2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
LIBOR floor rate			1.00%	1.00%
Interest rate description						The senior secured term loans (the “2015 Loans”) under the 2015 Term Loan Facility bore interest, at each borrower’s option, at a rate equal to either the LIBOR, plus an applicable margin of 3.50% per year (subject to a 1.00% LIBOR floor), or the adjusted base rate plus 2.50%. The adjusted base rate was defined as the greater of (a) LIBOR (using one-month interest period) plus 1.00%, (b) prime rate, (c) fed funds plus 0.5%, and (d) 2.00%. HPI borrowed the full $400.0 million available on the 2015 Term Loan Facility on May 7, 2015 as a LIBOR-based borrowing.
Maturity date of debt instrument						May 7, 2015
Line of credit facility maximum borrowing capacity				$ 400,000,000
Percentage on incremental loans effective yield maximum deduction			0.50%
Debt instrument effective yield percentage			5.00%
2015 Term Loan Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Line of credit facility borrowing capacity				$ 400,000,000
Debt instrument variable rate			4.00%	3.50%
2015 Term Loan Facility [Member] | Adjusted Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument variable rate				2.50%
2016 Incremental Loan Facility [Member]
Debt Instrument [Line Items]
LIBOR floor rate			1.00%
Maturity date of debt instrument						Oct. 25, 2016
2016 Incremental Loan Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt instrument variable rate			4.50%
2016 Incremental Loan Facility [Member] | Adjusted Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument variable rate			3.50%
2016 Incremental Loan Facility and 2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
Repayment of refinanced loans, amount		$ 769,000,000
Loss on debt extinguishment		$ (500,000)
Prepayment penalty fee percentage		1.00%
Incremental of debt discount and deferred financing fees capitalized		$ 5,800,000
Horizon Pharma USA Inc [Member] | 2024 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument						Nov. 1, 2024
Senior notes			$ 300,000,000
Net proceeds from senior notes			$ 291,900,000
Debt instrument redemption description						If the Company undergoes a change of control, the 2024 Issuers will be required to make an offer to purchase all of the 2024 Senior Notes at a price in cash equal to 101% of the aggregate principal amount thereof plus accrued and unpaid interest to, but not including, the repurchase date. If the Company or certain of its subsidiaries engages in certain asset sales, the 2024 Issuers will be required under certain circumstances to make an offer to purchase the 2024 Senior Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the repurchase date.
Redemption price percentage of principal amount of debt instrument on change of control			101.00%
Horizon Pharma USA Inc [Member] | October 2017 Refinancing Loans [Member]
Debt Instrument [Line Items]
Line of credit facility borrowing capacity	$ 845,800,000
Horizon Pharma USA Inc [Member] | 2016 Incremental Loan Facility [Member]
Debt Instrument [Line Items]
Line of credit facility borrowing capacity			$ 375,000,000
Hyperion Therapeutics, Inc. [Member] | 2023 Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument						May 1, 2023
Debt instrument redemption description						If the Company undergoes a change of control, HPI will be required to make an offer to purchase all of the 2023 Senior Notes at a price in cash equal to 101% of the aggregate principal amount thereof plus accrued and unpaid interest to, but not including, the repurchase date. If the Company or certain of its subsidiaries engages in certain asset sales, HPI will be required under certain circumstances to make an offer to purchase the 2023 Senior Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the repurchase date.
Redemption price percentage of principal amount of debt instrument on change of control					101.00%
Hyperion Therapeutics, Inc. [Member] | 2017 Term Loan Facility [Member] | 2017 Offering [Member]
Debt Instrument [Line Items]
Debt instrument, fair value						$ 848,900,000
Horizon Pharma Financing Inc. [Member] | 2023 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes					$ 475,000,000
Interest rate					6.625%
Net proceeds from senior notes					$ 462,300,000
Raptor Pharmaceutical Corp [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount			375,000,000
Raptor Pharmaceutical Corp [Member] | 2024 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes			$ 300,000,000
Interest rate			8.75%
Raptor Pharmaceutical Corp [Member] | 2016 Incremental Loan Facility [Member] | 2024 Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount			$ 375,000,000

Other Long-Term Liabilities - A

Other Long-Term Liabilities - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Long-term Liabilities [Member] | PROCYSBI and QUINSAIR [Member]
Other Long Term Liabilities [Line Items]
Fair value of long-term portion of contingent liability for royalties potentially payable	$ 26.4	$ 25.5

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Office Space Lease Agreements in Place for Real Properties (Detail) - ft²		12 Months Ended
		Dec. 31, 2017		Jun. 30, 2017
Dublin Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		18,900
Lease Expiry Date		Nov. 3, 2029
Lake Forest Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage	[1]	160,000
Lease Expiry Date	[1]	Mar. 31, 2024
Novato Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage	[2]	61,000
Lease Expiry Date	[2]	Aug. 31, 2021
Deerfield Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		32,300	[3]	32,300
Lease Expiry Date	[3]	Jun. 30, 2018
Brisbane Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		20,100
Lease Expiry Date		Nov. 30, 2019
Mannheim Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		14,300
Lease Expiry Date		Dec. 31, 2018
Chicago Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		6,500
Lease Expiry Date		Dec. 31, 2018
Other Office
Loss Contingencies [Line Items]
Approximate Square Footage		13,300
Other Office | Minimum [Member]
Loss Contingencies [Line Items]
Lease Expiry Date		Mar. 31, 2018
Other Office | Maximum [Member]
Loss Contingencies [Line Items]
Lease Expiry Date		May 31, 2020
[1]	In connection with the Lake Forest lease, the Company has provided a $2.0 million letter of credit to the landlord, through a commercial bank.
[2]	During March 2017, the Company vacated an area of the office space in Novato, California. During March and April 2017, the Company entered into sublease arrangements for this space with third parties.
[3]	During January 2016, the Company vacated the premises in Deerfield, Illinois and began occupying the premises in Lake Forest, Illinois. During April 2017, the Company entered into a sublease arrangement for a portion of this space with a third party. During June 2017, the Company terminated a portion of the lease, resulting in 32,300 square feet remaining.

Commitments and Contingencies92

Commitments and Contingencies - Schedule of Office Space Lease Agreements in Place for Real Properties (Parenthetical) (Detail) $ in Millions		Dec. 31, 2017USD ($)ft²		Jun. 30, 2017ft²
Lake Forest Office [Member]
Loss Contingencies [Line Items]
Letter of credit | $		$ 2
Approximate Square Footage	[1]	160,000
Deerfield Office [Member]
Loss Contingencies [Line Items]
Approximate Square Footage		32,300	[2]	32,300
[1]	In connection with the Lake Forest lease, the Company has provided a $2.0 million letter of credit to the landlord, through a commercial bank.
[2]	During January 2016, the Company vacated the premises in Deerfield, Illinois and began occupying the premises in Lake Forest, Illinois. During April 2017, the Company entered into a sublease arrangement for a portion of this space with a third party. During June 2017, the Company terminated a portion of the lease, resulting in 32,300 square feet remaining.

Commitments and Contingencies93

Commitments and Contingencies - Additional Information (Detail)	May 08, 2017USD ($)$ / SFr	Nov. 08, 2016USD ($)	Dec. 31, 2017USD ($)$ / €$ / SFr	Dec. 31, 2017CHF (SFr)	Dec. 31, 2016USD ($)€ / $	Dec. 31, 2015USD ($)	Dec. 12, 2017USD ($)	May 08, 2017CHF (SFr)$ / SFr
Loss Contingencies [Line Items]
Rent expense			$ 6,400,000		$ 5,100,000	$ 2,500,000
Royalty and royalty accretion expense			$ 82,300,000		$ 46,500,000	$ 45,500,000
River Vision [Member]
Loss Contingencies [Line Items]
Currency exchange rate | $ / SFr	1.0169		1.0263					1.0169
Maximum payment to be made upon attainment of milestones	$ 325,000,000		$ 105,700,000					SFr 103,000,000
Upfront cash payments	150,300,000		2,000,000	SFr 2,000,000
Cash acquired from acquisition	$ 6,300,000
Percentage of net sales in earn-out payment	3.00%
Net sales minimum limit for royal payment	$ 300,000,000
Minimum [Member] | River Vision [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment	9.00%
Maximum [Member] | River Vision [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment	12.00%
Cost of Goods Sold [Member]
Loss Contingencies [Line Items]
Royalty and royalty accretion expense			700,000
Selling, General and Administrative [Member]
Loss Contingencies [Line Items]
Royalty and royalty accretion expense			81,600,000
ACTIMMUNE Developed Technology [Member]
Loss Contingencies [Line Items]
Currency exchange rate | € / $					1.052
RAVICTI, BUPHENYL, QUINSAIR, VIMOVO and MIGERGOT [Member]
Loss Contingencies [Line Items]
Purchase and other commitments outstanding purchase orders			12,400,000
Teprotumumab [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment			$ 2,800,000
HZN-003 [Member] | MedImmune [Member]
Loss Contingencies [Line Items]
Maximum payment to be made upon attainment of milestones							$ 153,500,000
Upfront cash payment							$ 12,000,000
Boehringer Ingelheim [Member] | Cost of Goods Sold [Member]
Loss Contingencies [Line Items]
Recorded loss on non-cancellable and unconditional purchase commitments					$ 14,300,000
Manufacturing and Supply Agreement [Member] | Patheon Pharmaceuticals Inc. [Member] | PROCYSBI Developed Technology [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2010-11	2010-11
Minimum binding purchase commitment			$ 1,800,000
Supply agreement expiry date			Dec. 31, 2019	Dec. 31, 2019
Manufacturing and Supply Agreement [Member] | Cambrex [Member] | PROCYSBI API [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2010-11	2010-11
Minimum binding purchase commitment			$ 2,400,000
Supply agreement expiry date			Nov. 30, 2020	Nov. 30, 2020
Manufacturing and Supply Agreement [Member] | Boehringer Ingelheim [Member] | ACTIMMUNE Developed Technology [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2013-07	2013-07
Minimum binding purchase commitment			$ 24,300,000
Currency exchange rate | $ / €			1.2003
Recorded loss on non-cancellable and unconditional purchase commitments			$ 14,300,000
Additional costs committed to be incurred for harmonization of drug substance manufacturing process					$ 14,900,000
Costs related to harmonization of drug substance manufacturing process			12,100
Manufacturing and Supply Agreement [Member] | Boehringer Ingelheim [Member] | ACTIMMUNE Developed Technology [Member] | Cost of Goods Sold [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment			$ 1,700
Manufacturing and Supply Agreement [Member] | Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date					2007-03
Minimum binding purchase commitment					$ 48,000,000
Supply agreement expiry date					Dec. 31, 2030
Term of agreement automatically renewal period					3 years
Written notice period for termination of agreement					3 years
Expected early termination period of agreement due to uncertain event					Jan. 1, 2024
Other commitment					$ 2,800,000
Manufacturing and Supply Agreement [Member] | Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Purchase obligation percentage					80.00%
Manufacturing and Supply Agreement [Member] | Jagotec AG [Member] | LODOTRA /RAYOS [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2007-08	2007-08
Minimum binding purchase commitment			$ 6,700,000
Purchase commitment expiration date			Dec. 31, 2023	Dec. 31, 2023
Purchase commitment outstanding purchase orders			$ 500,000
Manufacturing and Supply Agreement [Member] | Nuvo Research Inc. [Member] | PENNSAID 2% [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2014-10	2014-10
Minimum binding purchase commitment			$ 2,700,000
Supply agreement expiry date			Dec. 31, 2029	Dec. 31, 2029
Manufacturing and Supply Agreement [Member] | Sanofi-Aventis U.S [Member] | DUEXIS [Member]
Loss Contingencies [Line Items]
Manufacturing and supply agreement initiation date			2011-05	2011-05
Minimum binding purchase commitment			$ 7,100,000
Term of agreement automatically renewal period			2 years	2 years
Written notice period for termination of agreement			2 years	2 years
Term of agreement expiration month and year			2019-05	2019-05
Amended and Restated License Agreement [Member] | PROCYSBI Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum annual royalty obligations			$ 100,000
Aggregate developement milestone payments amount for orphan indication			300,000
Aggregate regulatory milestone payments amount for orphan indication			1,800,000
Aggregate developement milestone payments amount for non-orphan indication			800,000
Aggregate regulatory milestone payments amount for non-orphan indication			3,500,000
License Agreement [Member] | Genentech Inc [Member] | ACTIMMUNE Developed Technology [Member]
Loss Contingencies [Line Items]
Net sales threshold			$ 3,700,000
License Agreement [Member] | Genentech Inc [Member] | ACTIMMUNE Developed Technology [Member] | Minimum [Member] | For First 3.7 Million in Net Sales [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales			20.00%	20.00%
License Agreement [Member] | Genentech Inc [Member] | ACTIMMUNE Developed Technology [Member] | Minimum [Member] | For All Additional Net Sales [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales			1.00%	1.00%
License Agreement [Member] | Genentech Inc [Member] | ACTIMMUNE Developed Technology [Member] | Maximum [Member] | For First 3.7 Million in Net Sales [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales			30.00%	30.00%
License Agreement [Member] | Genentech Inc [Member] | ACTIMMUNE Developed Technology [Member] | Maximum [Member] | For All Additional Net Sales [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales			9.00%	9.00%
License Agreement [Member] | Duke [Member] | KRYSTEXXA Developed Technology [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales revenue			5.00%	5.00%
License Agreement [Member] | Duke [Member] | KRYSTEXXA Developed Technology [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales revenue			15.00%	15.00%
License Agreement [Member] | MVP [ Member] | KRYSTEXXA Developed Technology [Member] | Minimum [Member] | Non-US [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales revenue			5.00%	5.00%
License Agreement [Member] | MVP [ Member] | KRYSTEXXA Developed Technology [Member] | Maximum [Member] | Non-US [Member]
Loss Contingencies [Line Items]
Percentage of royalty on net sales revenue			15.00%	15.00%
License Agreement [Member] | Aralez Pharmaceuticals Inc. [Member] | Vimovo and Other Medicines [Member]
Loss Contingencies [Line Items]
Minimum annual royalty obligations			$ 7,500,000
Percentage of royalty on net sales			10.00%	10.00%
Royalty expiration period upon first commercial sale in United States			10 years	10 years
Collaboration and Option Agreement [Member] | Privately-held life-science entity [Member]
Loss Contingencies [Line Items]
Payment of option to acquire assets		$ 100,000
Payment to acquire assets		25,000,000
Maximum payment to be made upon attainment of milestones		$ 9,800,000
Upfront cash payments			$ 2,600,000		$ 2,600,000

Commitments and Contingencies94

Commitments and Contingencies - Schedule of Minimum Future Cash Payments Due under Lease Obligations (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating Lease obligations, 2018	$ 7,356
Operating Lease obligations, 2019	6,659
Operating Lease obligations, 2020	5,951
Operating Lease obligations, 2021	5,350
Operating Lease obligations, 2022	4,092
Operating Lease obligations, Thereafter	11,994
Operating Lease obligations, Total	$ 41,402

Legal Proceedings - Additional

Legal Proceedings - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Legal Proceedings Related to RAVICTI [Member] | U.S. Patent No. 8,404,215 [Member]
Legal Proceedings [Line Items]
Expiry of patent	2032-03
Legal Proceedings Related to RAVICTI [Member] | U.S. Patent No. 8,642,012 [Member]
Legal Proceedings [Line Items]
Expiry of patent	2030-09
Legal Proceedings Related to RAVICTI [Member] | U.S. Patent No. 5,968,979 [Member]
Legal Proceedings [Line Items]
Expired date of patent	Feb. 7, 2015
Extended Expiry date of patent	Feb. 7, 2016
Final extension term granted by USPTO	1267 days
Legal Proceedings Related to RAYOS [Member] | Teva Settlement Agreement [Member]
Legal Proceedings [Line Items]
Settlement and license agreement date	Oct. 1, 2015
License agreement generic entry date	Dec. 23, 2022
Non-exclusive license agreement term	180 days
Legal Proceedings Related to PENNSAID 2% [Member] | Perrigo Settlement Agreement [Member]
Legal Proceedings [Line Items]
Settlement and license agreement date	May 6, 2015
Effective date of settlement and license agreement	January 10, 2029
Legal Proceedings Related to PENNSAID 2% [Member] | Taro Settlement Agreement [Member]
Legal Proceedings [Line Items]
Settlement and license agreement date	Sep. 9, 2015
Effective date of settlement and license agreement	January 10, 2029
Legal Proceedings Related to PENNSAID 2% [Member] | Teligent Settlement Agreement [Member]
Legal Proceedings [Line Items]
Settlement and license agreement date	May 9, 2016
Effective date of settlement and license agreement	January 10, 2029
Legal Proceedings Related to PENNSAID 2% [Member] | Amneal settlement agreement [Member]
Legal Proceedings [Line Items]
Settlement and license agreement date	Apr. 18, 2016
Effective date of settlement and license agreement	January 10, 2029

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 31, 2017	Jan. 01, 2017	May 31, 2016
Subsidiary Sale Of Stock [Line Items]
Shares issued during period in connection with stock option exercises, vesting of restricted stock, employee share purchase plan purchases and vesting of performance stock units	2,000,000
Proceeds from stock option exercises, issuances of restricted stock, employee share purchase plan purchases and vesting of performance stock units	$ 9,200
Ordinary shares issued upon cash exercise of warrants	391,500
Proceeds from aggregate exercise price	$ 1,800
Additional number of warrants exercised	704,285
Ordinary shares issuance in cashless exercises	523,520
Number of warrants outstanding	0
Payments for employee withholding taxes related to share-based payment	$ 6,533	$ 5,539	$ 3,024
Effect of ASU 2016-09 adoption on tax benefits	(1,252,329)	$ (848,021)
Total consideration for repurchase of ordinary shares, value	$ 992
2016 Repurchase Program [Member] | Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Shares authorized under repurchase program						5,000,000
2017 Repurchase Program [Member]
Subsidiary Sale Of Stock [Line Items]
Shares repurchased during period	100,000
Total consideration for repurchase of ordinary shares, value	$ 1,000
2017 Repurchase Program [Member] | Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Shares authorized under repurchase program				16,000,000
ASU 2016-09 [Member]
Subsidiary Sale Of Stock [Line Items]
Effect of ASU 2016-09 adoption on tax benefits					$ 7,200
Employee Stock Purchase Plans [Member]
Subsidiary Sale Of Stock [Line Items]
Payments for employee withholding taxes related to share-based payment	$ 6,500

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - USD ($)

Mar. 23, 2015

Jul. 28, 2011

Jan. 31, 2016

May 31, 2015

Mar. 31, 2015

Dec. 31, 2015

Sep. 30, 2015

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 23, 2017

Nov. 05, 2014

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Options, Granted

2,077,215

Stock options contractual term

10 years

Options granted to purchase common stock

2,077,215

2,057,247

8,010,638

Weighted average fair value of options granted to purchase common stock

$ 7.96

$ 11.58

$ 16.07

Total intrinsic value of options exercised

$ 2,600,000

$ 6,900,000

$ 15,600,000

Total fair value of stock options vested

41,300,000

55,600,000

11,400,000

Share-based compensation expense

121,553,000

114,144,000

85,786,000

ASU 2016-09 [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Tax benefit recognized from stock-based compensation expense

2,800

0

Tax benefits recognized from stock options exercised and vested restricted stock units

2,800

0

Pre-tax unrecognized compensation expense for all unvested share-based awards

$ 124,900,000

Cash Long-Term Incentive Program [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Trading days

20 days

Implied 20-day VWAP

$ 18.37

Bonus payable under cash bonus program

$ 15,800,000

Cash Bonus Program, description

Participants in the Cash Bonus Program were eligible for a specified cash bonus. The Cash Bonus Program pool funding of approximately $15.8 million was determined based on the Company’s actual TSR over the period from November 5, 2014 to May 6, 2015, and the bonus could be earned and payable only if the TSR for the period from November 5, 2014 to November 4, 2017 was greater than 15%. The portion of the total bonus pool payable to individual participants was based on allocations established by the Committee. Participants must have remained employed by the Company through November 4, 2017 unless a participant’s earlier departure from employment was due to death, disability, termination without cause or a change in control transaction. During the year ended December 31, 2017, the TSR did not exceed the minimum target requirement of 15% and the Cash Bonus Program expired without payment.

TSR, minimum target requirement percentage

15.00%

Estimated fair value of award

4,800,000

Reduction in expense related to cash bonus program

$ 3,500,000

Accrued amount related to cash bonus program

$ 0

Minimum [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted stock units, vesting period

2 years

Cash bonus payment date

Nov. 4, 2017

Minimum [Member] | Cash Long-Term Incentive Program [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Cash Bonus Program, percentage

15.00%

Maximum [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted stock units, vesting period

4 years

Restricted Stock Units [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

3,732,035

Weighted Average Grant Date Fair Value

$ 12.44

Total fair value of restricted stock units vested

$ 18,000,000

$ 16,200,000

$ 9,000,000

Restricted Stock Units [Member] | Employees and Nonexecutive Directors [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

3,732,035

1,384,104

2,361,948

Weighted Average Grant Date Fair Value

$ 12.44

$ 17.07

$ 23.36

Performance Stock Units [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

260,000

7,854,880

Weighted Average Grant Date Fair Value

$ 14.82

Trading days

20 days

Implied 20-day VWAP

$ 21.50

Share-based compensation expense

$ 49,600,000

$ 48,600,000

$ 37,700,000

Deferred tax assets related to share-based compensation expense

$ 16,400,000

Performance Stock Units [Member] | ASU 2016-09 [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Deferred tax assets related to share-based compensation expense

$ 16,400,000

Performance Stock Units [Member] | Minimum [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Percentage of outstanding PSU award vesting amount range

25.00%

Performance Stock Units [Member] | Maximum [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Percentage of outstanding PSU award vesting amount range

100.00%

Performance Stock Units [Member] | New And Promoted Key Employees [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

1,264,000

Performance Stock Units [Member] | Executive Committee And New Key Employees [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

1,120,000

Performance Stock Units [Member] | Nonmembers of Executive Committee [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

388,000

Performance Stock Units [Member] | Members of Executive Committee [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

One year mandatory post vest holding period percentage

50.00%

Two year mandatory post vest holding period percentage

50.00%

Performance Stock Units [Member] | Non-Executive Committee Members [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

1,840,443

Weighted Average Grant Date Fair Value

$ 13.71

One year mandatory post vest holding period percentage

50.00%

Initial Performance Stock Units [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

10,604,000

2014 ESPP [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock shares authorized

3,002,169

Common stock shares reserved for future issuance

3,002,169

2005 Plan [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Options, Granted

0

2014 EIP [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock shares authorized

3,885,178

Common stock shares reserved for future issuance

3,885,178

2014 EIP [Member] | 2017 Inducement Pool [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock shares authorized

356,636

Common stock shares reserved for future issuance

356,636

2014 Non-Employee Equity Plan [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock shares authorized

499,913

Common stock shares reserved for future issuance

499,913

2014 Equity Incentive Plan [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Restricted shares granted to purchase common stock

7,998,000

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options, Outstanding Beginning Balance	13,627,519
Options, Granted	2,077,215
Options, Exercised	(338,467)
Options, Forfeited	(644,752)
Options, Expired	(446,199)
Options, Outstanding Ending Balance	14,275,316	13,627,519
Options, Vested and Expected to vest as of December 31, 2017	13,789,210
Options, Exercisable as of December 31, 2017	9,365,306
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 18.17
Weighted Average Exercise Price, Granted	16.40
Weighted Average Exercise Price, Exercised	6.27
Weighted Average Exercise Price, Forfeited	18.37
Weighted Average Exercise Price, Expired	22.75
Weighted Average Exercise Price, Outstanding Ending Balance	18.04	$ 18.17
Weighted Average Exercise Price, Vested and Expected to vest as of December 31, 2017	18.02
Weighted Average Exercise Price, Exercisable as of December 31, 2017	$ 16.96
Weighted Average Contractual Term Remaining (in years)	6 years 11 months 19 days	7 years 7 months 6 days
Weighted Average Contractual Term Remaining (in years) Vested and Expected to vest as of December 31, 2017	6 years 11 months 1 day
Weighted Average Contractual Term Remaining (in years) Exercisable as of December 31, 2017	6 years 4 months 9 days
Aggregate Intrinsic Value	$ 25,005	$ 35,157
Aggregate Intrinsic Value, Exercised	2,600	$ 6,900	$ 15,600
Aggregate Intrinsic Value, Vested and Expected to vest as of December 31, 2017	24,960
Aggregate Intrinsic Value, Exercisable as of December 31, 2017	$ 24,158

Equity Incentive Plans - Summ99

Equity Incentive Plans - Summary of Outstanding Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of options outstanding	14,275,316
Options Outstanding, Weighted Average Exercise Price	$ 18.04	$ 18.17
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	6 years 11 months 19 days
Options Exercisable, Number Exercisable	9,365,306
Options Exercisable, Weighted Average Exercisable	$ 16.96
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	6 years 4 months 9 days
Exercise Price Ranges, $2.01 - $4.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 2.01
Range of Exercise Prices, Upper Range	$ 4
Options Outstanding, Number of options outstanding	742,582
Options Outstanding, Weighted Average Exercise Price	$ 2.67
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	5 years 29 days
Options Exercisable, Number Exercisable	742,582
Options Exercisable, Weighted Average Exercisable	$ 2.67
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	5 years 29 days
Exercise Price Ranges, $4.01 - $8.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 4.01
Range of Exercise Prices, Upper Range	$ 8
Options Outstanding, Number of options outstanding	1,209,543
Options Outstanding, Weighted Average Exercise Price	$ 6.29
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	4 years 6 months 25 days
Options Exercisable, Number Exercisable	1,199,789
Options Exercisable, Weighted Average Exercisable	$ 6.28
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	4 years 6 months 21 days
Exercise Price Ranges, $8.01 - $12.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 8.01
Range of Exercise Prices, Upper Range	$ 12
Options Outstanding, Number of options outstanding	721,063
Options Outstanding, Weighted Average Exercise Price	$ 9.19
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	5 years 4 months 28 days
Options Exercisable, Number Exercisable	677,499
Options Exercisable, Weighted Average Exercisable	$ 9.17
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	5 years 4 months 2 days
Exercise Price Ranges, $12.01 - $17.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 12.01
Range of Exercise Prices, Upper Range	$ 17
Options Outstanding, Number of options outstanding	2,552,212
Options Outstanding, Weighted Average Exercise Price	$ 14.12
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	6 years 10 months 13 days
Options Exercisable, Number Exercisable	1,810,195
Options Exercisable, Weighted Average Exercisable	$ 14.05
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	6 years 1 month 9 days
Exercise Price Ranges, $17.01 - $22.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 17.01
Range of Exercise Prices, Upper Range	$ 22
Options Outstanding, Number of options outstanding	3,252,701
Options Outstanding, Weighted Average Exercise Price	$ 18.11
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	8 years 3 months 29 days
Options Exercisable, Number Exercisable	1,018,088
Options Exercisable, Weighted Average Exercisable	$ 18.83
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	7 years 6 months 3 days
Exercise Price Ranges, $22.01 - $28.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 22.01
Range of Exercise Prices, Upper Range	$ 28
Options Outstanding, Number of options outstanding	3,412,700
Options Outstanding, Weighted Average Exercise Price	$ 22.31
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	7 years 2 months 26 days
Options Exercisable, Number Exercisable	2,342,100
Options Exercisable, Weighted Average Exercisable	$ 22.30
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	7 years 2 months 23 days
Exercise Price Ranges, $28.01 - $36.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 28.01
Range of Exercise Prices, Upper Range	$ 36
Options Outstanding, Number of options outstanding	2,384,515
Options Outstanding, Weighted Average Exercise Price	$ 29.47
Options Outstanding, Weighted Average Remaining Contractual Term(in years)	7 years 1 month 20 days
Options Exercisable, Number Exercisable	1,575,053
Options Exercisable, Weighted Average Exercisable	$ 29.39
Options Exercisable, Weighted Average Remaining Contractual Term(in years)	7 years 3 days

Equity Incentive Plans - Weight

Equity Incentive Plans - Weighted Average Fair Value per Share of Stock Option Awards Granted and Assumptions Used to Value Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate, minimum	1.80%	1.30%	1.30%
Risk-free interest rate, maximum	2.20%	2.20%	2.20%
Weighted average volatility	49.10%	73.20%	77.10%
Expected life (in years)	5 years 11 months 26 days	6 years 7 days	6 years 25 days
Weighted average grant date fair value per share of options granted	$ 7.96	$ 11.58	$ 16.07

Equity Incentive Plans - Sum101

Equity Incentive Plans - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Outstanding Beginning Balance | shares	3,367,871
Number of Units, Granted | shares	3,732,035
Number of Units, Vested | shares	(1,222,920)
Number of Units, Forfeited | shares	(593,136)
Number of Units, Outstanding Ending Balance | shares	5,283,850
Weighted Average Grant-Date Fair Value Per Unit, Outstanding Beginning Balance | $ / shares	$ 18.45
Weighted Average Grant-Date Fair Value Per Unit, Granted | $ / shares	12.44
Weighted Average Grant-Date Fair Value Per Unit, Vested | $ / shares	16.78
Weighted Average Grant-Date Fair Value Per Unit, Forfeited | $ / shares	16.85
Weighted Average Grant-Date Fair Value Per Unit, Outstanding Ending Balance | $ / shares	$ 14.77

Equity Incentive Plans - Sum102

Equity Incentive Plans - Summary of Performance Stock Unit Awards Activity (Detail) - Performance Stock Units [Member]	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Outstanding Beginning Balance | shares	12,045,656
Number of Units, Vested and issued | shares	(25,000)
Number of Units, Expired | shares	(3,927,440)	[1]
Number of Units, Forfeited | shares	(238,336)
Number of Units, Outstanding Ending Balance | shares	7,854,880
Weighted Average Grant-Date Fair Value Per Unit, Vested and issued	$ 12.36
Weighted Average Grant-Date Fair Value Per Unit, Expired	14.82	[1]
Weighted Average Grant-Date Fair Value Per Unit, Forfeited	$ 10.86
Average Illiquidity discount, Vested and issued	0.00%
Average Illiquidity discount, Expired	14.90%	[1]
Average Illiquidity discount, Forfeited	7.50%
Recorded Weighted Average Fair Value Per Unit, Vested and issued	$ 13.30
Recorded Weighted Average Fair Value Per Unit, Expired	12.60	[1]
Recorded Weighted Average Fair Value Per Unit, Forfeited	$ 10.04
[1]	During the year ended December 31, 2017, the first of three tranches of the Company’s outstanding PSUs expired due to failure to meet the Company’s minimum total compounded annual shareholder rate of return (“TSR”) requirement.

Equity Incentive Plans - Sum103

Equity Incentive Plans - Summary of Performance Stock Unit Awards Activity (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017Tranche
Performance Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of tranches	3

Equity Incentive Plans - Sum104

Equity Incentive Plans - Summary of Vesting Tranches (Detail)	12 Months Ended
	Dec. 31, 2017
Performance Stock Units [Member] | Tranche Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	33.30%
Beginning of Performance Measurement Period	Mar. 23, 2015
End of Performance Measurement Period	Mar. 22, 2018
Performance Stock Units [Member] | Tranche Three [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	33.30%
Beginning of Performance Measurement Period	Mar. 23, 2015
End of Performance Measurement Period	Jun. 22, 2018
Performance Stock Units [Member] | Vesting Amount 25% [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	25.00%
TSR Achieved	15.00%
Performance Stock Units [Member] | Vesting Amount 50% [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	50.00%
TSR Achieved	30.00%
Performance Stock Units [Member] | Vesting Amount 75% [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	75.00%
TSR Achieved	45.00%
Performance Stock Units [Member] | Vesting Amount 100% [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percent of Total PSU Award	100.00%
TSR Achieved	60.00%
Initial Performance Stock Units [Member] | Tranche Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Length of Performance Measurement Period (Years)	3 years
Initial Performance Stock Units [Member] | Tranche Three [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Length of Performance Measurement Period (Years)	3 years 3 months

Equity Incentive Plans - Sum105

Equity Incentive Plans - Summary of Significant Valuation Assumption (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk free rate, minimum	1.80%	1.30%	1.30%
Risk free rate, maximum	2.20%	2.20%	2.20%
Expected volatility	49.10%	73.20%	77.10%
Cash Long-Term Incentive Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Valuation date stock price		$ 16.18	$ 21.67
Expected volatility		74.70%	74.80%
Risk-free rate		0.78%	1.00%
Performance Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum		76.80%	64.60%
Expected volatility, maximum		77.60%	72.30%
Risk free rate, minimum		1.00%	1.00%
Risk free rate, maximum		1.20%	1.10%
Performance Stock Units [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Valuation date stock price		$ 17.72	$ 16.81
Performance Stock Units [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Valuation date stock price		$ 21.07	$ 35.06

Equity Incentive Plans - Sum106

Equity Incentive Plans - Summary of Average Estimated Fair Value of PSU after Applicable Discount of Illiquidity (Detail) - Performance Stock Units [Member] - $ / shares	1 Months Ended	12 Months Ended
	Jan. 31, 2016	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Granted	260,000	7,854,880
Weighted Average Fair Value Per Unit		$ 14.82
Average Illiquidity Discount		14.90%
Recorded Weighted Average Fair Value Per Unit		$ 12.60
Executive Committee Members [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Granted		6,014,437
Weighted Average Fair Value Per Unit		$ 15.16
Average Illiquidity Discount		17.10%
Recorded Weighted Average Fair Value Per Unit		$ 12.57
Non-Executive Committee Members [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Granted		1,840,443
Weighted Average Fair Value Per Unit		$ 13.71
Average Illiquidity Discount		7.30%
Recorded Weighted Average Fair Value Per Unit		$ 12.71

Equity Incentive Plans - Sum107

Equity Incentive Plans - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 121,553	$ 114,144	$ 85,786
Cost of Goods Sold [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	2,469	26
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	9,263	9,413	6,590
Selling, General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 109,821	$ 104,705	$ 79,196

Income Taxes - Company's (Loss)

Income Taxes - Company's (Loss) Income Before Benefit for Income Taxes by Jurisdiction (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
United States	$ (271,102)	$ (165,476)	$ (198,442)
Loss before benefit for income taxes	(513,275)	(228,085)	(132,712)
Other Foreign [Member]
Income Tax Contingency [Line Items]
(Loss) before benefit for income taxes, Foreign	(225,217)	(34,654)	76,476
Ireland [Member]
Income Tax Contingency [Line Items]
(Loss) before benefit for income taxes, Foreign	$ (16,956)	$ (27,955)	$ (10,746)

Income Taxes - Components of be

Income Taxes - Components of benefit for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current provision
Total current provision	$ 15,838	$ 12,357	$ 8,607
Deferred (benefit) provision
Total deferred benefit	(118,587)	(73,608)	(180,851)
Effective income taxes	(102,749)	(61,251)	(172,244)
U.S. - Federal and State [Member]
Current provision
Total current provision	12,085	10,491	6,355
Deferred (benefit) provision
Total deferred benefit	(120,111)	(69,073)	(175,228)
Other Foreign [Member]
Current provision
Total current provision	831	679	328
Deferred (benefit) provision
Total deferred benefit	7,818	(2,481)
Ireland [Member]
Current provision
Total current provision	2,922	1,187	1,924
Deferred (benefit) provision
Total deferred benefit	$ (6,294)	$ (2,054)	$ (5,623)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	Jun. 22, 2018	Mar. 22, 2018	Dec. 23, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 08, 2017
Income Taxes [Line Items]
Benefit for income taxes					$ (102,749,000)	$ (61,251,000)	$ (172,244,000)
Current income tax provision					15,838,000	12,357,000	8,607,000
Deferred tax benefit					(118,587,000)	$ (73,608,000)	$ (180,851,000)
Tax Cuts and Jobs Act of 2017, incomplete accounting, provisional income tax expense (benefit)					(74,900,000)
Impact of Tax Cuts and Jobs Act of 2017 on deferred taxes					(134,182,000)
Write-off of U.S. deferred tax asset related to interest expense carryforwards due to the Tax Act					$ 59,243,000
Effective income tax rate					20.00%	26.90%	129.80%
Effective income tax statutory income tax rate					12.50%	12.50%	12.50%
Notional interest deduction					$ 27,020,000	$ 35,075,000	$ 22,848,000
Tax charges on intragroup profits					8,888,000	(2,154,000)	9,955,000
U.S. federal and state tax credits					3,608,000	3,613,000
Change in U.S. state effective tax rate					2,329,000	17,246,000	9,061,000
Tax effect on non-deductible IPR&D expenses					51,148,000
Tax effect on non-deductible share-based compensation expenses					26,811,000	7,125,000	3,776,000
Tax effect on increase in uncertain tax positions					4,976,000	2,837,000	3,012,000
Increase in non-deductible share-based compensation					19,700,000
Decrease in benefit from change in U.S. state effective tax rate					14,900,000
Decrease in tax charges of intragroup profit					11,000,000
Decrease in benefit realized on notional interest deduction					8,100,000
Decrease in changes in valuation allowances					$ 4,700,000
Operating loss carryforwards limitations on use					Net operating loss carryovers in Switzerland have a seven-year carryforward life and started to expire in 2016 due to lack of sufficient taxable income to fully absorb the available carryover loss.
Increase (decrease) in the deferred tax valuation allowance					$ (6,900,000)	1,200,000	(80,200,000)
Unrecognized tax benefits, long term liabilities					6,400,000
Deferred income tax assets, net					17,000,000
Interest expense					1,300,000	600,000
Penalties expense					200,000	100,000
Income tax penalties and interest expense					24,900,000
Performance Stock Units [Member]
Income Taxes [Line Items]
Number of trading days require for share price			20 days
Deferred tax assets related to share-based compensation expense			$ 16,400,000
Performance Stock Units [Member] | Maximum [Member]
Income Taxes [Line Items]
Share price			$ 31.58
Fiscal Year 2014 [Member]
Income Taxes [Line Items]
Operating loss carry forward annual limitation					50,000,000
Fiscal Year 2018 to 2028 [Member]
Income Taxes [Line Items]
Operating loss carry forward annual limitation					7,700,000
Fiscal Year 2009 [Member]
Income Taxes [Line Items]
Operating loss carry forward annual limitation					200,000
Ireland [Member]
Income Taxes [Line Items]
Current income tax provision					2,922,000	1,187,000	1,924,000
Deferred tax benefit					(6,294,000)	$ (2,054,000)	$ (5,623,000)
Provision for income tax on undistributed earnings of subsidiaries					0
Unremitted earnings					339,200,000
Estimates income tax unremitted earnings					0
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					$ 114,400,000
Operating loss carryforward, expiration year					2,020
Federal [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Operating loss carryforward, expiration year					2,030
Operating loss carryforwards limitations on use					The U.S. federal orphan drug credits and the U.S. federal research and development credits will both begin to expire in 2030. The U.S. federal alternative minimum tax credits and California research and development credits have indefinite lives and therefore are not subject to expiration. The EDGE credits have a five-year carryforward life following the year of generation and will begin to expire in 2019.
Income tax credit carryforwards					$ 56,600,000
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					$ 307,400,000
Operating loss carryforward, expiration year					2,016
State [Member] | Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Income tax credit carryforwards					$ 6,200,000
Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					149,300,000
River Vision [Member]
Income Taxes [Line Items]
Tax effect on non-deductible IPR&D expenses					51,100,000
Income tax credit carryforwards								$ 5,800,000
River Vision [Member] | Fiscal Year 2018 through 2020 [Member]
Income Taxes [Line Items]
Operating loss carry forward annual limitation					$ 12,500,000
Scenario Forecast [Member]
Income Taxes [Line Items]
U.S. federal corporate tax rate				21.00%
Scenario Forecast [Member] | Performance Stock Units [Member]
Income Taxes [Line Items]
Number of trading days require for share price	20 days	20 days
Deferred tax assets related to share-based compensation expense	$ 8,400,000	$ 9,300,000
Scenario Forecast [Member] | Performance Stock Units [Member] | Maximum [Member]
Income Taxes [Line Items]
Share price	$ 33.86	$ 32.70

Income Taxes - Reconciliation B

Income Taxes - Reconciliation Between Irish Rate and U.S Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Irish income tax at statutory rate (12.5%)	$ (64,159)	$ (28,510)	$ (16,586)
Foreign tax rate differential	(9,806)	(1,893)	(30,348)
Impact of the Tax Act on deferred taxes	(134,182)
Write-off of U.S. deferred tax asset related to interest expense carryforwards due to the Tax Act	59,243
Notional interest deduction	(27,020)	(35,075)	(22,848)
Non-deductible in-process research and development costs	51,148
Share-based compensation	26,811	7,125	3,776
Transaction costs	341	3,447	3,109
Disallowed interest	2,990	2,620	2,139
Disqualified compensation expense	1,305	2,555	3,949
Uncertain tax positions	4,976	2,837	3,012
Tax charges on intragroup profit	(8,888)	2,154	(9,955)
U.S. state income taxes	214	8,579	1,002
Change in U.S. state effective tax rate	(2,329)	(17,246)	(9,061)
Change in valuation allowances	(1,378)	(6,117)	(106,834)
U.S. federal and state tax credits	(3,608)	(3,613)
Interest expense on convertible debt inducements			(1,218)
Book loss on debt extinguishment			6,396
Other, net	1,593	1,886	1,223
Benefit for income taxes	$ (102,749)	$ (61,251)	$ (172,244)
Effective income tax rate	20.00%	26.90%	129.80%

Income Taxes - Reconciliatio112

Income Taxes - Reconciliation Between Irish Rate and U.S Federal Statutory Income Tax Rate (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Irish income tax statutory rate, Percentage	12.50%	12.50%	12.50%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 65,650	$ 99,004
Capital loss carryforwards	2,796	4,631
Alternative minimum tax credit	13,972	5,922
State net operating losses	35,465	48,758
Accrued compensation	46,420	65,733
Accruals and reserves	11,089	20,179
Contingent royalties	33,436	68,628
Intercompany interest		54,703
Other	2,259
Total deferred tax assets	211,087	367,558
Valuation allowance	(25,650)	(32,532)	$ (31,310)	$ (111,555)
Deferred tax assets, net of valuation allowance	185,437	335,026
Deferred tax liabilities:
Inventories	570	13,077
Debt discount	23,372	23,050
Intangible assets	315,970	593,057
Other		1,499
Total deferred tax liabilities	339,912	630,683
Net deferred income tax liability	$ 154,475	$ 295,657

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Beginning and Ending Amounts of Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning Balance	$ (32,532)	$ (31,310)	$ (111,555)
Increase for year activity	(6,835)	(14,636)	(37,569)
Release of valuation allowances	5,313	15,056	117,814
Additions to valuation allowances due to acquisitions		(1,642)
Decreases to valuation allowances due to divestiture	8,404
Ending Balance	$ (25,650)	$ (32,532)	$ (31,310)

Income Taxes - Changes in Uncer

Income Taxes - Changes in Uncertain Income Tax Positions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning balance – uncertain tax positions	$ 17,747	$ 9,812	$ 775
Additions	2,451	471	2,604
Acquired uncertain tax positions		5,362	6,433
Additions	4,145	2,102
Settlements and lapses	(939)
Ending balance – uncertain tax positions	$ 23,404	$ 17,747	$ 9,812

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan expenses	$ 4.9	$ 2.7	$ 2.1
Percent of matching contribution by company	100.00%
Maximum percent of employee's elective contribution to plan	3.00%
Percent of employee's eligible pay	2.00%
Defined benefit plan expenses	$ 0.4	0.4	0.2
Deferred compensation plan liabilities	6.5	3.1
Deferred compensation plan assets funds held	6.5	3.1
Non-qualified deferred compensation plan expenses recognized	$ 0.8	$ 0.6	$ 0.2
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of matching contribution by company	50.00%

Selected Quarterly Financial117

Selected Quarterly Financial Information (Unaudited) - Summary of Selected Financial Results of Operations (Detail) - 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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 274,219	$ 271,646	$ 289,507	$ 220,859	$ 310,350	$ 208,702	$ 257,378	$ 204,690	$ 1,056,231	$ 981,120	$ 757,044
Gross profit	122,727	146,129	159,357	81,743	160,598	123,541	176,252	127,457	509,956	587,848	537,542
Operating (loss) income	(75,568)	(25,751)	(185,667)	(105,383)	(130,108)	(21,322)	31,467	(27,204)	$ (392,369)	$ (147,167)	$ 55,372
Net (loss) income	$ (46,449)	$ (63,971)	$ (209,536)	$ (90,570)	$ (130,542)	$ (5,870)	$ 14,984	$ (45,406)
Net (loss) income per ordinary share - basic	$ (0.28)	$ (0.39)	$ (1.29)	$ (0.56)	$ (0.81)	$ (0.04)	$ 0.09	$ (0.28)	$ (2.52)	$ (1.04)	$ 0.27
Net (loss) income per ordinary share - diluted	$ (0.28)	$ (0.39)	$ (1.29)	$ (0.56)	$ (0.81)	$ (0.04)	$ 0.09	$ (0.28)	$ (2.52)	$ (1.04)	$ 0.25

Schedule II - Valuation and 118

Schedule II - Valuation and Qualifying Accounts (Detail) - Allowance for discounts and returns [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 21,916	$ 14,964	$ 4,483
Acquisitions/(Divestitures)		1,234	236
Additions, Charged to costs and expenses	125,851	81,089	55,702
Deductions from reserves	(100,671)	(75,371)	(45,457)
Ending Balance	$ 47,096	$ 21,916	$ 14,964