Horizon Therapeutics Public (HZNP) 10-Q 4 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 29, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Title of 12(b) Security	Ordinary shares, nominal value $0.0001 per share
Trading Symbol	HZNP
Security Exchange Name	NASDAQ
Entity Registrant Name	HORIZON THERAPEUTICS PUBLIC LIMITED COMPANY
Entity Central Index Key	0001492426
Entity Tax Identification Number	00-0000000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		225,893,375
Entity Shell Company	false
Entity File Number	001-35238
Entity Incorporation, State or Country Code	L2
Entity Address, Address Line One	Connaught House, 1st Floor
Entity Address, Address Line Two	1 Burlington Road
Entity Address, City or Town	Dublin 4
Entity Address, Postal Zip Code	D04 C5Y6
Entity Address, Country	IE
City Area Code	011
Local Phone Number	353 1 772 2100
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 812,319	$ 2,079,906
Restricted cash	3,839	3,573
Accounts receivable, net	735,433	659,701
Inventories, net	258,676	75,283
Prepaid expenses and other current assets	365,113	251,945
Total current assets	2,175,380	3,070,408
Property and equipment, net	220,142	189,037
Developed technology and other intangible assets, net	3,119,709	1,782,962
In-process research and development	880,000
Goodwill	1,069,031	413,669
Deferred tax assets, net	610,559	560,841
Other assets	132,595	55,699
Total assets	8,207,416	6,072,616
CURRENT LIABILITIES:
Accounts payable	51,947	37,710
Accrued expenses and other current liabilities	478,499	485,567
Accrued trade discounts and rebates	306,364	352,463
Long-term debt—current portion	16,000
Total current liabilities	852,810	875,740
LONG-TERM LIABILITIES:
Long-term debt, net	2,560,444	1,003,379
Deferred tax liabilities, net	549,078	66,474
Other long-term liabilities	171,448	101,672
Total long-term liabilities	3,280,970	1,171,525
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS’ EQUITY:
Ordinary shares, $0.0001 nominal value; 600,000,000 shares authorized at June 30, 2021 and December 31, 2020; 226,099,787 and 221,721,674 shares issued at June 30, 2021 and December 31, 2020, respectively, and 225,715,421 and 221,337,308 shares outstanding at June 30, 2021 and December 31, 2020, respectively	22	22
Treasury stock, 384,366 ordinary shares at June 30, 2021 and December 31, 2020	(4,585)	(4,585)
Additional paid-in capital	4,260,337	4,245,945
Accumulated other comprehensive loss	(1,018)	(145)
Accumulated deficit	(181,120)	(215,886)
Total shareholders’ equity	4,073,636	4,025,351
Total liabilities and shareholders' equity	$ 8,207,416	$ 6,072,616

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Ordinary shares, nominal value	$ 0.0001	$ 0.0001
Ordinary shares, shares authorized	600,000,000	600,000,000
Ordinary shares, shares issued	226,099,787	221,721,674
Ordinary shares, shares outstanding	225,715,421	221,337,308
Treasury stock, ordinary shares	384,366	384,366

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net sales	$ 832,548	$ 462,779	$ 1,174,954	$ 818,688
Cost of goods sold	200,995	121,515	301,363	218,931
Gross profit	631,553	341,264	873,591	599,757
OPERATING EXPENSES:
Research and development	139,834	81,068	197,527	108,277
Selling, general and administrative	355,204	222,332	687,196	470,107
Impairment of long-lived asset		1,072	12,371	1,072
Gain on sale of asset	(2,000)		(2,000)
Total operating expenses	493,038	303,400	895,094	578,384
Operating income (loss)	138,515	37,864	(21,503)	21,373
OTHER EXPENSE, NET:
Interest expense, net	(22,581)	(18,571)	(36,041)	(35,915)
Loss on debt extinguishment		(17,254)		(17,254)
Foreign exchange (loss) gain	(39)	283	(887)	1,059
Other (expense) income, net	(262)	632	2,962	1,074
Total other expense, net	(22,882)	(34,910)	(33,966)	(51,036)
Income (loss) before (benefit) expense for income taxes	115,633	2,954	(55,469)	(29,663)
(Benefit) expense for income taxes	(42,484)	82,964	(90,235)	63,938
Net income (loss)	$ 158,117	$ (80,010)	$ 34,766	$ (93,601)
Net income (loss) per ordinary share—basic	$ 0.70	$ (0.42)	$ 0.15	$ (0.49)
Weighted average ordinary shares outstanding—basic	225,119,684	192,705,535	224,523,538	191,426,864
Net income (loss) per ordinary share—diluted	$ 0.67	$ (0.42)	$ 0.15	$ (0.49)
Weighted average ordinary shares outstanding—diluted	235,191,860	192,705,535	234,719,830	191,426,864
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX
Foreign currency translation adjustments	$ 235	$ 344	$ (586)	$ 19
Pension remeasurements			(287)
Other comprehensive income (loss)	235	344	(873)	19
Comprehensive income (loss)	$ 158,352	$ (79,666)	$ 33,893	$ (93,582)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2019	$ 2,185,449	$ 19	$ (4,585)	$ 2,797,602	$ (1,905)	$ (605,682)
Beginning balance, shares at Dec. 31, 2019		188,402,040	384,366
Issuance of ordinary shares in conjunction with the exercise of stock options and the vesting of restricted stock and performance stock units	7,049			7,049
Issuance of ordinary shares in conjunction with the exercise of stock options, shares		2,560,573
Ordinary shares withheld for payment of employees’ withholding tax liability	(46,664)			(46,664)
Share-based compensation	56,421			56,421
Currency translation adjustment	(325)				(325)
Net income (loss)	(13,591)					(13,591)
Ending balance at Mar. 31, 2020	2,188,339	$ 19	$ (4,585)	2,814,408	(2,230)	(619,273)
Ending balance, shares at Mar. 31, 2020		190,962,613	384,366
Beginning balance at Dec. 31, 2019	2,185,449	$ 19	$ (4,585)	2,797,602	(1,905)	(605,682)
Beginning balance, shares at Dec. 31, 2019		188,402,040	384,366
Currency translation adjustment	19
Net income (loss)	(93,601)
Ending balance at Jun. 30, 2020	2,361,852	$ 20	$ (4,585)	3,067,586	(1,886)	(699,283)
Ending balance, shares at Jun. 30, 2020		199,991,807	384,366
Beginning balance at Mar. 31, 2020	2,188,339	$ 19	$ (4,585)	2,814,408	(2,230)	(619,273)
Beginning balance, shares at Mar. 31, 2020		190,962,613	384,366
Issuance of ordinary shares in conjunction with the exercise of stock options and the vesting of restricted stock and performance stock units	18,838			18,838
Issuance of ordinary shares in conjunction with the exercise of stock options, shares		1,427,108
Issuance of ordinary shares in conjunction with Employee Share Purchase Plan	7,979			7,979
Issuance of ordinary shares in conjunction with Employee Share Purchase Plan, Shares		376,718
Issuance of ordinary shares in conjunction with 2.5% Exchangeable Senior Notes due 2022	205,650	$ 1		205,649
Issuance of ordinary shares in conjunction with 2.5% Exchangeable Senior Notes due 2022, shares		7,225,368
Ordinary shares withheld for payment of employees’ withholding tax liability	(6,345)			(6,345)
Share-based compensation	27,057			27,057
Currency translation adjustment	344				344
Net income (loss)	(80,010)					(80,010)
Ending balance at Jun. 30, 2020	2,361,852	$ 20	$ (4,585)	3,067,586	(1,886)	(699,283)
Ending balance, shares at Jun. 30, 2020		199,991,807	384,366
Beginning balance at Dec. 31, 2020	4,025,351	$ 22	$ (4,585)	4,245,945	(145)	(215,886)
Beginning balance, shares at Dec. 31, 2020		221,721,674	384,366
Issuance of ordinary shares in conjunction with the exercise of stock options and the vesting of restricted stock and performance stock units	19,843			19,843
Issuance of ordinary shares in conjunction with the exercise of stock options, shares		3,305,947
Ordinary shares withheld for payment of employees’ withholding tax liability	(128,261)			(128,261)
Share-based compensation	62,296			62,296
Currency translation adjustment	(821)				(821)
Pension remeasurements	(287)				(287)
Net income (loss)	(123,351)					(123,351)
Ending balance at Mar. 31, 2021	3,854,770	$ 22	$ (4,585)	4,199,823	(1,253)	(339,237)
Ending balance, shares at Mar. 31, 2021		225,027,621	384,366
Beginning balance at Dec. 31, 2020	4,025,351	$ 22	$ (4,585)	4,245,945	(145)	(215,886)
Beginning balance, shares at Dec. 31, 2020		221,721,674	384,366
Currency translation adjustment	(586)
Pension remeasurements	287
Net income (loss)	34,766
Ending balance at Jun. 30, 2021	4,073,636	$ 22	$ (4,585)	4,260,337	(1,018)	(181,120)
Ending balance, shares at Jun. 30, 2021		226,099,787	384,366
Beginning balance at Mar. 31, 2021	3,854,770	$ 22	$ (4,585)	4,199,823	(1,253)	(339,237)
Beginning balance, shares at Mar. 31, 2021		225,027,621	384,366
Issuance of ordinary shares in conjunction with the exercise of stock options and the vesting of restricted stock and performance stock units	7,996			7,996
Issuance of ordinary shares in conjunction with the exercise of stock options, shares		597,169
Issuance of ordinary shares in conjunction with Employee Share Purchase Plan	11,482			11,482
Issuance of ordinary shares in conjunction with Employee Share Purchase Plan, Shares		474,997
Ordinary shares withheld for payment of employees’ withholding tax liability	(13,388)			(13,388)
Share-based compensation	54,424			54,424
Currency translation adjustment	235				235
Net income (loss)	158,117					158,117
Ending balance at Jun. 30, 2021	$ 4,073,636	$ 22	$ (4,585)	$ 4,260,337	$ (1,018)	$ (181,120)
Ending balance, shares at Jun. 30, 2021		226,099,787	384,366

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)			$ 34,766	$ (93,601)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense			162,736	139,396
Equity-settled share-based compensation			115,590	83,478
Acquired in-process research and development expense			46,500	47,517
Impairment of long-lived asset		$ 1,072	12,371	1,072
Amortization of debt discount and deferred financing costs			2,240	10,817
Loss on debt extinguishment		17,254		17,254
Gain on sale of asset	$ (2,000)		(2,000)
Deferred income taxes			(18,115)	(4,561)
Foreign exchange and other adjustments			(3,452)	661
Changes in operating assets and liabilities:
Accounts receivable			(68,014)	(135,125)
Inventories			(31,713)	(12,343)
Prepaid expenses and other current assets			(95,123)	(20,410)
Accounts payable			10,306	83,555
Accrued trade discounts and rebates			(48,013)	(177,721)
Accrued expenses and other current liabilities			(24,641)	81,505
Other non-current assets and liabilities			(7,764)	16,586
Net cash provided by operating activities			85,674	37,008
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired			(2,775,330)	(262,305)
Purchases of property and equipment			(32,255)	(119,970)
Payments for long-term investments, net			(7,578)
Change in escrow deposit for property purchase				6,000
Net cash used in investing activities			(2,815,163)	(376,275)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from term loans			1,574,993
Repayment of term loans			(4,000)
Proceeds from the issuance of ordinary shares in conjunction with Employee Share Purchase Plan			11,482	7,979
Proceeds from the issuance of ordinary shares in connection with stock option exercises			27,839	25,887
Payment of employee withholding taxes relating to share-based awards			(141,648)	(53,009)
Net cash provided by (used in) financing activities			1,468,666	(19,143)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash			(6,498)	58
Net decrease in cash, cash equivalents and restricted cash			(1,267,321)	(358,352)
Cash, cash equivalents and restricted cash, beginning of the period			2,083,479	1,080,039	$ 1,080,039
Cash, cash equivalents and restricted cash, end of the period	$ 816,158	$ 721,687	816,158	721,687	$ 2,083,479
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest			32,102	30,068
Cash paid for amounts included in the measurement of lease liabilities			5,218	3,797
Cash paid for income taxes, net of refunds received			13,435	597
SUPPLEMENTAL NON-CASH FLOW INFORMATION:
Lease liabilities arising from obtaining right-of-use assets			62,156
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities			$ 18,180	2,912
Principal amount of 2.5% Exchangeable Senior Notes due 2022 converted into ordinary shares				207,044
Milestone payments for TEPEZZA intangible asset included in accrued expenses and other current liabilities				$ 98,606

Basis of Presentation and Busin

Basis of Presentation and Business Overview	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and Business Overview	NOTE 1 – BASIS OF PRESENTATION AND BUSINESS OVERVIEW Basis of Presentation Unless otherwise indicated or the context otherwise requires, references to “Horizon”, the “Company”, “we”, “us” and “our” refer to Horizon Therapeutics plc and its consolidated subsidiaries. On March 15, 2021, the Company completed its acquisition of Viela Bio, Inc. (“Viela”) and acquired all of the issued and outstanding shares of Viela’s common stock for $53.00 per share. The total consideration for the acquisition was approximately $3.0 billion, including cash acquired of $342.3 million. Following the completion of the acquisition, Viela became a wholly-owned subsidiary of the Company. The unaudited condensed consolidated financial statements presented herein include the results of operations of the acquired business from the date of acquisition. The unaudited condensed consolidated financial statements presented herein have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, the financial statements do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, all adjustments, including normal recurring adjustments, considered necessary for a fair statement of the financial statements have been included. Operating results for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. The December 31, 2020 condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by GAAP. Business Overview Horizon is focused on researching, developing and commercializing medicines that address critical needs for people impacted by rare, autoimmune and serious inflammatory diseases. The Company’s pipeline is purposeful: it applies scientific expertise and courage to bring clinically meaningful therapies to patients. Horizon believes science and compassion must work together to transform lives. The Company has two reportable segments, the orphan segment and the inflammation segment, and its portfolio is currently composed of 12 marketed medicines in the areas of rare diseases, gout, ophthalmology and inflammation. As of June 30, 2021, the Company’s marketed medicines consisted of the following: Orphan TEPEZZA ® KRYSTEXXA ® RAVICTI ® PROCYSBI ® ACTIMMUNE ® UPLIZNA ® BUPHENYL ® QUINSAIR™ (levofloxacin) solution for inhalation Inflammation PENNSAID ® DUEXIS ® RAYOS ® VIMOVO ®

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2 – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES 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. In December 2019, the FASB issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplification and reduce the cost of accounting for income taxes Other recent authoritative guidance issued by the FASB (including technical corrections to the Accounting Standards Codification (“ASC”)), the American Institute of Certified Public Accountants and the Securities and Exchange Commission (“SEC”) did not, or are not expected to, have a material impact on the Company’s condensed consolidated financial statements and related disclosures. Significant Accounting Policies The Company’s significant accounting policies have not changed from those previously described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The following accounting policy relating to intangible assets is disclosed in connection with the Viela acquisition. Intangible Assets 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 intangibles, 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.

Net Income (Loss) per Share

Net Income (Loss) per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Income (Loss) per Share	NOTE 3 – NET INCOME (LOSS) PER SHARE The following table presents basic and diluted net income (loss) per share for the three and six months ended June 30, 2021 and 2020 (in thousands, except share and per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Basic net income (loss) per share calculation: Numerator - net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 ) Denominator - weighted average ordinary shares outstanding 225,119,684 192,705,535 224,523,538 191,426,864 Basic net income (loss) per share $ 0.70 $ (0.42 ) $ 0.15 $ (0.49 ) For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Diluted net income (loss) per share calculation: Numerator - net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 ) Denominator - weighted average ordinary shares outstanding 235,191,860 192,705,535 234,719,830 191,426,864 Diluted net income (loss) per share $ 0.67 $ (0.42 ) $ 0.15 $ (0.49 ) Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of ordinary shares outstanding during the period. Diluted net income (loss) per share reflects the potential dilution 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. During the three and six months ended June 30, 2021, the difference between the basic and diluted weighted average ordinary shares outstanding , represents the effect of incremental shares from the Company’s share-based compensation progra ms. The computation of diluted net income (loss) per share excluded 0.9 million and 2.9 million shares subject to equity awards for the three and six months ended June 30, 2021, respectively, because their inclusion would have had an anti-dilutive effect on diluted net income (loss) per share. The computation of diluted net income (loss) per share excluded 9.7 million and 12.0 million shares subject to equity awards for the three and six months ended June 30, 2020, respectively, and 12.4 million and 13.1 million shares (based on the if-converted method) related to the Company’s 2.5% Exchangeable Senior Notes due 2022 (the “Exchangeable Senior Notes”) for the three and six months ended June 30, 2020, respectively, because their inclusion would have had an anti-dilutive effect on diluted net income (loss) per share. On August 3, 2020, the Exchangeable Senior Notes were fully extinguished through exchanges for ordinary shares or cash redemption.

Acquisitions, Divestitures and

Acquisitions, Divestitures and Other Arrangements	6 Months Ended
	Jun. 30, 2021
Business Combinations [Abstract]
Acquisitions, Divestitures and Other Arrangements	NOTE 4 – ACQUISITIONS, DIVESTITURES AND OTHER ARRANGEMENTS Acquisition of Viela On March 15, 2021, the Company completed its acquisition of Viela and acquired all of the issued and outstanding shares of Viela’s common stock for $53.00 per share. The acquisition added an additional rare disease medicine, UPLIZNA, to the Company’s medicine portfolio. The Viela acquisition provides multiple opportunities to drive long-term growth and solidify the Company’s future as an innovation-driven biotech company. Viela’s mid-stage biologics pipeline, research and development (“R&D”) team and on-market medicine UPLIZNA, make it a complementary strategic fit with the Company’s pipeline, commercial portfolio and therapeutic areas of focus. Following completion of the acquisition, Viela became a wholly-owned subsidiary of the Company. The Company financed the transaction through cash on hand and $1.6 billion of aggregate principal amount of term loans pursuant to Company’s existing credit agreement, as described in Note 13. The total consideration for the acquisition was approximately $3.0 billion, including cash acquired of $342.3 million, and was composed of the following (in thousands): E quity value (54,988,820 shares at $53.00 per share) $ 2,914,407 Net settlements on the exercise of stock options 78,554 Consideration for exchange of Viela stock options 1,130 Total consideration $ 2,994,091 During the six months ended June 30, 2021, the Company incurred $28.6 million in Viela transaction costs, including advisory, legal, accounting, valuation and other Pursuant to ASC 805, Business Combinations (“ASC 805”), the Company accounted for the Viela acquisition as a business combination using the acquisition method of accounting. Identifiable assets and liabilities of Viela, 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. The valuation of assets acquired and liabilities assumed has not yet been finalized as of June 30, 2021. While all amounts remain subject to adjustments, the areas subject to the most significant potential adjustments are inventory, intangible assets, IPR&D and deferred income taxes. As a result, the Company recorded preliminary estimates for the fair value of assets acquired and liabilities assumed as of the acquisition date. Such preliminary 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. Accordingly, the purchase price adjustments are preliminary and are subject to further adjustments as additional information becomes available and as additional analyses are performed, and such further adjustments may be material. The Company’s management believes the fair values recognized for the assets acquired and the liabilities assumed are based on reasonable estimates and assumptions. During the three months ended June 30, 2021 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): Before Adjustments After Deferred tax liabilities, net $ (457,928 ) $ 6,869 $ (451,059 ) Accrued expenses and other current liabilities (73,401 ) (335 ) (73,736 ) Other long-term liabilities (22,631 ) — (22,631 ) Accounts payable (4,768 ) — (4,768 ) Accrued trade discounts and rebates (1,492 ) (373 ) (1,865 ) Marketable securities 400 — 400 Property, plant and equipment 1,747 — 1,747 Other assets 3,253 — 3,253 Accounts receivable 8,053 (267 ) 7,786 Prepaid expenses and other current assets 16,444 (837 ) 15,607 Inventories 149,348 2,300 151,648 Cash and cash equivalents 342,347 — 342,347 In-process research and development 910,000 — 910,000 Developed technology 1,460,000 — 1,460,000 (Liabilities assumed) and assets acquired 2,331,372 7,357 2,338,729 Goodwill 662,719 (7,357 ) 655,362 Fair value of consideration paid $ 2,994,091 $ — $ 2,994,091 Inventories acquired included raw materials, work in process and finished goods for UPLIZNA. Inventories were recorded at their preliminary estimated fair values. The fair value of finished goods has been determined based on the estimated selling price, net of selling costs and a margin on the selling activities. The fair value of work in process has been determined based on estimated selling price, net of selling costs and costs to complete the manufacturing, and a margin on the selling and manufacturing activities. The fair value of raw materials was estimated to equal the replacement cost. A step-up in the value of inventory of $149.3 million was originally recorded in connection with the acquisition, which was composed of $10.1 million for raw materials, $119.0 million for work-in-process and $20.2 million for finished goods. During the three months ended June 30, 2021, the step-up in the value of inventory was increased to $151.6 million following the recording of $2.3 million in measurement period adjustments during the three months ended June 30, 2021, which was composed of $1.9 million for work-in-process and $0.4 million for finished goods. During the three and six months ended June 30, 2021, the Company recorded inventory step-up expense of $7.1 million and $8.0 million, respectively, related to UPLIZNA based on the acquired units sold during the period. Other tangible assets and liabilities were valued at their respective carrying amounts as management believes that these amounts approximated their acquisition-date fair values. Developed technology is an intangible asset that reflects the estimated fair value of the rights to UPLIZNA in the United States. The preliminary estimated fair values of the developed technology represent preliminary valuations performed with the assistance of an independent appraisal firm based on management’s estimates, forecasted financial information and reasonable and supportable assumptions. The preliminary 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 UPLIZNA. Indications of value were developed by discounting these benefits to their acquisition-date fair value at a discount rate of 11.5% that reflects the return requirements of the market. Some of the most significant assumptions inherent in the development of the asset valuation include the estimated net cash flows for each year (including net sales, cost of goods sold, sales and marketing costs and R&D costs) and the discount rate. The fair value of the UPLIZNA developed technology was capitalized as of the Viela acquisition date and is subsequently being amortized over approximately 14 years. IPR&D is related to R&D projects including: (i) Potential regulatory approval of UPLIZNA for neuromyelitis optica spectrum disorder outside of the United States and certain other indications worldwide. As of the date of the acquisition, UPLIZNA had not been granted regulatory approval in any territory outside the United States. On March 24, 2021, the Company announced that its strategic partner, Mitsubishi Tanabe Pharma Corporation, had received manufacturing and marketing approval for UPLIZNA in Japan. Refer to Note 8 for further details. (ii) HZN-7734, an investigational human monoclonal antibody designed to deplete plasmacytoid dendritic cells (pDCs), a cell type believed to be critical to the pathogenesis of multiple autoimmune diseases. (iii) HZN-4920, an investigational fusion protein designed to block a key co-stimulatory pathway involved in many autoimmune and inflammatory diseases. Each IPR&D asset is considered separable from the business as each project could be sold to a third party. The fair value of each IPR&D asset 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 sales projections and estimated direct costs. Indications of value are developed by discounting these benefits to their present value at a discount rate of 12.5% that reflects the return requirements of the market. Some of the most significant assumptions inherent in the development of the asset valuations include the estimated net cash flows for each year (including net sales, cost of goods sold, sales and marketing costs and R&D costs), the discount rate, the assessment of each asset’s life cycle and the potential regulatory and commercial success risk. The fair value of the various IPR&D assets was recorded as an indefinite-lived intangible asset and will be tested for impairment until completion or abandonment of R&D efforts associated with the project. The Company reviews amounts capitalized as acquired IPR&D for impairment annually and whenever events or changes in circumstances indicate that the carrying value of the assets might not be recoverable. 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. The developed technology, IPR&D assets and inventory acquired through the Viela acquisition were located in the United States as of the acquisition date, where a U.S. tax rate of 23.8% is being utilized and a significant deferred tax liability of $451.1 million was recorded. Goodwill represents the excess of the total consideration over the estimated fair value of net assets acquired and was recorded in the consolidated balance sheet as of the acquisition date. The goodwill was primarily attributable to the establishment of a deferred tax liability for the developed technology intangible asset and the IPR&D intangible assets. Viela’s mid-stage biologics pipeline, R&D team and on-market medicine UPLIZNA, make it a complementary strategic fit with the Company’s pipeline, commercial portfolio and therapeutic areas of focus. The Company does not expect any portion of this goodwill to be deductible for tax purposes. The following table presents the pro forma combined results of the Company and Viela for the six months ended June 30, 2021 and 2020 as if the acquisition of Viela had occurred on January 1, 2020: For the Six Months Ended June 30, 2021 2020 As reported Pro forma adjustments Pro forma As reported Pro forma adjustments Pro forma Net sales $ 1,174,954 $ 10,588 $ 1,185,542 $ 818,688 $ — $ 818,688 Net income (loss) 34,766 (30,804 ) 3,962 (93,601 ) (166,290 ) (259,891 ) The pro forma combined financial information was prepared using the acquisition method of accounting and was based on the historical financial information of Horizon and Viela. In order to reflect the pro forma information as if the acquisition occurred on January 1, 2020 as required, the pro forma financial information includes adjustments to reflect incremental amortization expense to be incurred based on the current preliminary fair values of the identifiable intangible assets acquired; the incremental cost of products sold related to the fair value adjustments associated with acquisition date inventory; the additional interest expense associated with the issuance of debt to finance the acquisition; and the reclassification of transaction costs incurred during the six months ended June 30, 2021 to the six months ended June 30, 2020. Significant non-recurring pro forma adjustments include transaction costs of $86.6 million which were assumed to have been incurred on January 1, 2020 and were recognized as if incurred in the first half of 2020. The pro forma financial information is not necessarily indicative of what the consolidated results of operations would have been had the acquisition actually been completed on January 1, 2020. In addition, the pro forma financial information is not a projection of future results of operations of the combined company nor does it reflect the expected realization of any synergies or cost savings associated with the acquisition. Acquisition of Curzion Pharmaceuticals, Inc. On April 1, 2020, the Company acquired Curzion Pharmaceuticals, Inc. (“Curzion”), a privately held development-stage biopharma company, and its development-stage oral selective lysophosphatidic acid 1 receptor (LPAR 1 Under the terms of the acquisition agreement, the Company acquired Curzion for a $45.0 million upfront payment with additional payments contingent on the achievement of development and regulatory milestones. Pursuant to ASC 805, the Company accounted for the Curzion acquisition as the purchase of an IPR&D asset and, pursuant to ASC Topic 730, Research and Development, Refer to Note 15 for further detail on HZN-825 milestone payments. Sale of RAVICTI and BUPHENYL Rights in Japan On October 27, 2020, the Company sold its rights to develop and commercialize RAVICTI and BUPHENYL in Japan to Medical Need Europe AB, part of the Immedica Group, Acquisition of River Vision On May 8, 2017, the Company acquired 100% of the equity interests in River Vision Development Corp. (“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. Under the acquisition agreement for River Vision, the Company agreed to pay up to $325.0 million upon the attainment of various milestones, composed of $100.0 million related to U.S. Food and Drug Administration (“FDA”) approval and $225.0 million related to net sales thresholds for TEPEZZA. The agreement also includes a royalty payment of 3 percent of the portion of annual worldwide net sales exceeding $300.0 million. The Company made the milestone payment of $100.0 million related to FDA approval during the first quarter of 2020 which is now capitalized as a finite-lived intangible asset representing the developed technology for TEPEZZA. Additionally, under the Company’s license agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (together referred to as “Roche”), the Company made a milestone payment of CHF5.0 million ($5.2 million when converted using a CHF-to-Dollar exchange rate at the date of payment of 1.0382), during the first quarter of 2020 which the Company also capitalized as a finite-lived intangible asset representing the developed technology for TEPEZZA. In April 2020, a subsidiary of the Company entered into an agreement with S.R. One, Limited (“S.R. One”) and an agreement with Lundbeckfond Invest A/S (“Lundbeckfond”) p In addition, during the year ended December 31, 2020, the Company recorded $120.8 million as a finite-lived intangible asset representing the developed technology for TEPEZZA, composed of $67.0 million in relation to the expected future attainment of various net sales milestones payable under the acquisition agreement for River Vision and CHF50.0 million ($53.8 million when converted using a CHF-to-Dollar exchange rate as of the date the intangible asset was recorded) in relation to the expected future attainment of various net sales milestones payable to Roche. The liabilities relating to these TEPEZZA net sales milestones were recorded in accrued expenses and other current liabilities on the consolidated balance sheet as of December 31, 2020. The Company paid such TEPEZZA net sales milestones to Roche in February 2021 and to the former River Vision stockholders in April 2021 and, following such payments, there are no further TEPEZZA net sales milestone obligations remaining to Roche and the former River Vision stockholders. The Company’s remaining obligation to Roche relating to the attainment of various TEPEZZA development and regulatory milestones is CHF43.0 million ($46.5 million when converted using a CHF-to-Dollar exchange rate at June 30, 2021 of 1.0813). Licensing Agreements On June 18, 2021, the Company entered into a global agreement with Arrowhead Pharmaceuticals, Inc. (“Arrowhead”) for ARO-XDH, a previously undisclosed discovery-stage investigational RNA interference (“RNAi”) therapeutic being developed by Arrowhead as a potential treatment for uncontrolled gout. Arrowhead granted the Company a worldwide exclusive license to develop, manufacture and commercialize the RNAi therapeutic products. Arrowhead will conduct all research and preclinical development activities for the RNAi therapeutic. The Company must use commercially reasonable efforts in, and will be responsible for, clinical development and commercialization of the RNAi therapeutic products. Under the terms of the agreement, the Company paid Arrowhead an upfront cash payment of $40.0 million in July 2021 and agreed to pay additional potential future milestone payments of up to $660.0 million contingent on the achievement of certain development, regulatory and commercial milestones, and low to mid-teens royalties on worldwide calendar year net sales of licensed products. The $40.0 million upfront payment was accrued and accounted for as the acquisition of an IPR&D asset and was recorded as a “research and development” expense in the condensed consolidated statement of comprehensive income (loss) during the three and six months ended June 30, 2021. On November 21, 2020, the Company entered into a global agreement with Halozyme Therapeutics, Inc. (“Halozyme”) that gives the Company exclusive access to Halozyme’s ENHANZE ® Other Arrangements On January 3, 2019, the Company entered into an agreement with HemoShear Therapeutics, LLC (“HemoShear”), a biotechnology company, to discover novel therapeutic targets for gout. The agreement provides the Company with an opportunity to address unmet treatment needs for people with gout by evaluating new targets for the control of serum uric acid levels. Under the terms of the agreement, the Company paid HemoShear an upfront cash payment of $2.0 million with additional potential future milestone payments upon commencement of new stages of development, contingent on the Company’s approval at each stage. In June 2019, the Company incurred a $4.0 million progress payment, which was subsequently paid in July 2019.

Inventories

Inventories	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Inventories	NOTE 5 – INVENTORIES Inventories are stated at the lower of cost or net realizable 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 drug substance and finished goods inventories, and 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 June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Raw materials $ 53,112 $ 11,760 Work-in-process 90,840 33,167 Finished goods 114,724 30,356 Inventories, net $ 258,676 $ 75,283

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2021
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 June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Advance payments for inventory $ 134,716 $ 137,680 Deferred charge for taxes on intercompany profit 85,070 52,306 Prepaid income taxes and income tax receivable 63,609 102 Rabbi trust assets 23,885 18,423 Other prepaid expenses and other current assets 57,833 43,434 Prepaid expenses and other current assets $ 365,113 $ 251,945 Advance payments for inventory as of June 30, 2021 and December 31, 2020, primarily represented payments made to the contract manufacturer of TEPEZZA drug substance.

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	NOTE 7 – PROPERTY AND EQUIPMENT Property and equipment as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Buildings $ 128,266 $ 80,341 Land and land improvements 38,880 38,076 Construction in process 28,377 63,656 Machinery and equipment 16,669 4,695 Software 14,488 14,618 Furniture and fixtures 12,293 5,973 Leasehold improvements 9,847 26,323 Other 5,066 3,146 253,886 236,828 Less accumulated depreciation (33,744 ) (47,791 ) Property and equipment, net $ 220,142 $ 189,037 Depreciation expense was $3.4 million and $6.9 million for the three months ended June 30, 2021 and 2020, respectively, and was $7.8 million and $14.1 million for the six months ended June 30, 2021 and 2020, respectively. In February 2020, the Company purchased a three-building campus in Deerfield, Illinois for total consideration and directly attributable transaction costs of $118.5 million. The Deerfield campus totals 70 acres and consists of approximately 650,000 square feet of office space. The Company’s office employees previously located in Lake Forest, Illinois moved to the Deerfield campus in February 2021 and the Company is marketing its Lake Forest office space for sublease. The increase in amount classified as buildings and the decrease in amount classified as construction in process is primarily due to the Deerfield campus becoming operational in February 2021. The decreases in leasehold improvements and accumulated depreciation amounts are primarily due to the Company vacating the Lake Forest office building in February 2021.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2021
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 June 30, 2021 and December 31, 2020 was $1,069.0 million and $413.7 million, respectively. The table below presents goodwill for the Company’s reportable segments as of June 30, 2021 (in thousands): Orphan Inflammation Total Balance at December 31, 2020 $ 357,498 $ 56,171 $ 413,669 Goodwill recognized on acquisition of Viela 662,719 — 662,719 Adjustment relating to the acquisition of Viela (7,357 ) — (7,357 ) Balance at June 30, 2021 $ 1,012,860 $ 56,171 $ 1,069,031 In March 2021, the Company recognized goodwill with a preliminary value of $662.7 million in connection with the Viela acquisition, which represented the excess of the purchase price over the fair value of the net assets acquired. During the three months ended June 30, 2021, the Company recorded measurement period adjustments related to deferred tax liabilities, accounts receivable, prepaid expenses and other current assets, accrued expenses and other current liabilities As of June 30, 2021, there were no accumulated goodwill impairment losses. Intangible Assets As of June 30, 2021, the Company’s finite-lived intangible assets consisted of developed technology related to ACTIMMUNE, BUPHENYL, KRYSTEXXA, PROCYSBI, RAVICTI, RAYOS, TEPEZZA and UPLIZNA as well as customer relationships for ACTIMMUNE. The intangible assets related to PENNSAID 2%, and VIMOVO developed technology were fully amortized as of December 31, 2020. On March 15, 2021, in connection with the acquisition of Viela, the Company capitalized $1,460.0 million of developed technology related to UPLIZNA. See Note 4 for further details. In connection with the acquisition of River Vision, the Company capitalized payments of $336.0 million related to TEPEZZA developed technology during the year ended December 31, 2020. See Note 4 for further details on the River Vision acquisition. Intangible assets as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Cost Accumulated Amortization Net Book Value Cost Basis Accumulated Amortization Net Book Value Developed technology $ 4,585,524 $ (1,468,423 ) $ 3,117,101 $ 3,093,886 $ (1,313,934 ) $ 1,779,952 In-process research and development (1) 880,000 — 880,000 — — — Customer relationships 8,100 (5,492 ) 2,608 8,100 (5,090 ) 3,010 Total intangible assets $ 5,473,624 $ (1,473,915 ) $ 3,999,709 $ 3,101,986 $ (1,319,024 ) $ 1,782,962 (1) The Company acquired IPR&D of $910.0 million relating to Viela. On March 24, 2021, the Company announced that its strategic partner, Mitsubishi Tanabe Pharma Corporation, had received manufacturing and marketing approval of UPLIZNA in Japan. As a result, the Company transferred $30.0 million of IPR&D to developed technology. As of June 30, 2021, the remaining IPR&D relating to the Viela acquisition was $880.0 million. Amortization expense for the three months ended June 30, 2021 and 2020 was $88.5 million and $66.7 million, respectively, and was $154.9 million and $125.3 million for the six months ended June 30, 2021 and 2020, respectively. IPR&D is not amortized until successful completion of a project. As of June 30, 2021, estimated future amortization expense was as follows (in thousands): 2021 (July to December) $ 179,397 2022 354,891 2023 354,376 2024 352,951 2025 350,700 Thereafter 1,527,394 Total $ 3,119,709

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	NOTE 9 – ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Payroll-related expenses $ 108,720 $ 121,577 Accrued royalties 68,104 68,006 Accrued upfront and milestone payments 46,500 123,442 Allowances for returns 37,881 40,918 R&D and manufacturing programs 36,992 17,289 Advertising and marketing 28,505 12,428 Consulting and professional services 25,310 21,893 Deferred revenues 20,835 — Pricing review liability 20,068 16,046 Accrued interest 15,688 14,207 Accrued other 69,896 49,761 Accrued expenses and other current liabilities $ 478,499 $ 485,567

Accrued Trade Discounts and Reb

Accrued Trade Discounts and Rebates	6 Months Ended
	Jun. 30, 2021
Valuation And Qualifying Accounts Disclosure [Line Items]
Accrued Expenses and Other Current Liabilities	NOTE 9 – ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Payroll-related expenses $ 108,720 $ 121,577 Accrued royalties 68,104 68,006 Accrued upfront and milestone payments 46,500 123,442 Allowances for returns 37,881 40,918 R&D and manufacturing programs 36,992 17,289 Advertising and marketing 28,505 12,428 Consulting and professional services 25,310 21,893 Deferred revenues 20,835 — Pricing review liability 20,068 16,046 Accrued interest 15,688 14,207 Accrued other 69,896 49,761 Accrued expenses and other current liabilities $ 478,499 $ 485,567
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Accrued Expenses and Other Current Liabilities	NOTE 10 – ACCRUED TRADE DISCOUNTS AND REBATES Accrued trade discounts and rebates as of , 2020 (in thousands): June 30, 2021 December 31, 2020 Accrued government rebates and chargebacks $ 191,663 $ 172,893 Accrued co-pay and other patient assistance 60,799 96,924 Accrued commercial rebates and wholesaler fees 53,902 82,646 Accrued trade discounts and rebates $ 306,364 $ 352,463 Invoiced commercial rebates and wholesaler fees, co-pay and other patient assistance costs, and government rebates and chargebacks in accounts payable 10,324 1,452 Total customer-related accruals and allowances $ 316,688 $ 353,915 The following table summarizes changes in the Company’s customer-related accruals and allowances from December 31, 2020 to June 30, 2021 (in thousands): Government Co-Pay and Wholesaler Fees Rebates and Other Patient and Commercial Chargebacks Assistance Rebates Total Balance at December 31, 2020 $ 172,893 $ 96,924 $ 84,098 $ 353,915 Current provisions relating to sales during the six months ended June 30, 2021 342,609 404,720 145,684 893,013 Adjustments relating to prior-year sales (9,376 ) (4,516 ) (2,361 ) (16,253 ) Payments relating to sales during the six months ended June 30, 2021 (171,269 ) (344,328 ) (83,411 ) (599,008 ) Payments relating to prior-year sales (144,605 ) (92,012 ) (79,854 ) (316,471 ) Viela acquisition on March 15, 2021 1,411 11 70 1,492 Balance at June 30, 2021 $ 191,663 $ 60,799 $ 64,226 $ 316,688

Segment and Other Information

Segment and Other Information	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Segment and Other Information	NOTE 11 The Company has two reportable segments, the orphan segment and the inflammation segment, and the Company reports net sales and segment operating income for each segment. On March 15, 2021, the Company completed its acquisition of Viela. The acquisition expanded the Company’s medicine portfolio by adding an additional rare disease medicine, UPLIZNA, to its orphan segment. The orphan segment includes the medicines TEPEZZA, KRYSTEXXA, RAVICTI, PROCYSBI, ACTIMMUNE, UPLIZNA, BUPHENYL and QUINSAIR as well as the Company’s R&D programs. The inflammation segment includes the medicines PENNSAID 2%, DUEXIS, RAYOS and VIMOVO. The Company’s chief operating decision maker (“CODM”) evaluates the financial performance of the Company’s segments based upon segment operating income. Segment operating income is defined as loss before benefit for income taxes adjusted for the items set forth in the reconciliation below. Items below income from operations are not reported by segment, since they are excluded from the measure of segment profitability reviewed by the Company’s CODM. Additionally, certain expenses are not allocated to a segment. The Company does not report balance sheet information by segment as no balance sheet by segment is reviewed by the Company’s CODM. The following table reflects net sales by medicine for the Company’s reportable segments for the three and six months ended June 30, 2021 and 2020 (in thousands): Three Months Ended June 30 Six Months Ended June 30 2021 2020 2021 2020 TEPEZZA $ 453,255 $ 165,936 $ 455,320 $ 189,387 KRYSTEXXA 130,317 75,201 237,074 168,450 RAVICTI 68,426 65,550 141,243 126,738 PROCYSBI 49,775 41,357 93,138 79,700 ACTIMMUNE 27,777 28,299 56,540 54,840 UPLIZNA 14,475 — 16,348 — BUPHENYL 2,262 2,846 3,922 5,160 QUINSAIR 222 59 431 336 Orphan segment net sales $ 746,509 $ 379,248 $ 1,004,016 $ 624,611 PENNSAID 2% 48,941 35,048 94,758 76,611 DUEXIS 22,110 27,798 41,575 59,145 RAYOS 13,406 14,459 28,678 32,668 VIMOVO 1,582 6,226 5,927 25,653 Inflammation segment net sales $ 86,039 $ 83,531 $ 170,938 $ 194,077 Total net sales $ 832,548 $ 462,779 $ 1,174,954 $ 818,688 The table below provides reconciliations of the Company’s segment operating income to the Company’s total income (loss) before expense for income taxes for the three and six months ended June 30, 2021 and 2020 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Segment operating income: Orphan $ 321,235 $ 151,541 $ 322,289 $ 205,897 Inflammation 46,767 38,096 89,447 90,038 Reconciling items: Amortization and step-up: Intangible amortization expense (88,523 ) (66,749 ) (154,892 ) (125,324 ) Inventory step-up expense (7,091 ) — (8,002 ) — Share-based compensation (54,424 ) (27,057 ) (115,590 ) (83,478 ) Upfront, progress and milestone payments related to license and collaboration agreements (46,500 ) (3,000 ) (49,500 ) (3,000 ) Acquisition/divestiture-related costs (30,626 ) (46,988 ) (80,017 ) (47,272 ) Interest expense, net (22,581 ) (18,571 ) (36,041 ) (35,915 ) Depreciation (3,393 ) (6,907 ) (7,844 ) (14,072 ) Restructuring and realignment costs (930 ) — (7,023 ) — Other (expense) income, net (262 ) 632 2,962 1,074 Fees related to refinancing activities — — — (54 ) Foreign exchange (loss) gain (39 ) 283 (887 ) 1,059 Loss on debt extinguishment — (17,254 ) — (17,254 ) Impairment of long-lived assets — (1,072 ) (12,371 ) (1,072 ) Drug substance harmonization costs — — — (290 ) Gain on sale of asset 2,000 — 2,000 — Income (loss) before (benefit) expense for income taxes $ 115,633 $ 2,954 $ (55,469 ) $ (29,663 ) The following table presents the amount and percentage of gross sales to customers that represented more than 10% of the Company’s gross sales included in its two reportable segments and all other customers as a group for the three and six months ended June 30, 2021 and 2020 (in thousands, except percentages): For the Three Months Ended June 30, 2021 2020 Amount % of Amount % of Gross Sales Sales Customer A $ 410,436 31 % $ 314,288 35 % Customer B 342,148 26 % 194,576 22 % Customer C 240,290 18 % 160,814 18 % Customer D 212,820 16 % 112,676 13 % Other Customers 117,500 9 % 115,639 12 % Gross Sales $ 1,323,194 100 % $ 897,993 100 % For the Six Months Ended June 30, 2021 2020 Amount % of Amount % of Gross Sales Sales Customer A $ 659,176 32 % $ 561,063 33 % Customer B 526,835 25 % 401,853 24 % Customer C 358,327 17 % 294,689 17 % Customer D 303,439 15 % 197,464 12 % Other Customers 236,949 11 % 246,447 14 % Gross Sales $ 2,084,726 100 % $ 1,701,516 100 % Geographic revenues are determined based on the country in which the Company’s customers are located. The following table presents a summary of net sales attributed to geographic sources for the three and six months ended June 30, 2021 and 2020 (in thousands, except percentages): Three Months Ended June 30, 2021 Three Months Ended June 30, 2020 Amount % of Total Net Sales Amount % of Total Net Sales United States $ 830,185 100% $ 460,827 100% Rest of world 2,363 * 1,952 * Net sales $ 832,548 $ 462,779 *Less than 1% Six Months Ended June 30, 2021 Six Months Ended June 30, 2020 Amount % of Total Net Sales Amount % of Total Net Sales United States $ 1,170,515 100% $ 814,843 100% Rest of world 4,439 * 3,845 * Net sales $ 1,174,954 $ 818,688 *Less than 1%

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 12 – 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; and 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. 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. Assets and liabilities measured at fair value on a recurring basis The following tables set forth the Company’s financial assets and liabilities at fair value on a recurring basis as of June 30, 2021 and December 31, 2020 (in thousands): June 30, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 643,000 $ — $ — $ 643,000 Other current assets 23,885 — — 23,885 Total assets at fair value $ 666,885 $ — $ — $ 666,885 Liabilities: Other long-term liabilities (23,885 ) — — (23,885 ) Total liabilities at fair value $ (23,885 ) $ — $ — $ (23,885 ) December 31, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 1,906,000 — — $ 1,906,000 Other current assets 18,423 — — 18,423 Total assets at fair value $ 1,924,423 $ — $ — $ 1,924,423 Liabilities: Other long-term liabilities (18,423 ) — — (18,423 ) Total liabilities at fair value $ (18,423 ) $ — $ — $ (18,423 )

Debt Agreements

Debt Agreements	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt Agreements	NOTE 13 – DEBT AGREEMENTS The Company’s outstanding debt balances as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Term Loan Facility due 2028 $ 1,596,000 — Term Loan Facility due 2026 418,026 418,026 Senior Notes due 2027 600,000 600,000 Total face value 2,614,026 1,018,026 Debt discount (13,177 ) (10,061 ) Deferred financing fees (24,405 ) (4,586 ) Total long-term debt 2,576,444 1,003,379 Less: current maturities 16,000 — Long-term debt, net of current maturities $ 2,560,444 $ 1,003,379 Term Loan Facility and Revolving Credit Facility On March 15, 2021, Horizon Therapeutics USA, Inc. (formerly known as Horizon Pharma USA, Inc.) (the “Borrower” or “HTUSA”), a wholly-owned subsidiary of the Company, borrowed approximately $1.6 billion aggregate principal amount of loans (the “Incremental Loans”) pursuant to an amendment (the “March 2021 Amendment”) to the credit agreement, dated as of May 7, 2015, by and among the Borrower, 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, Amendment No. 2, dated March 29, 2017, Amendment No. 3, dated October 23, 2017, Amendment No. 4, dated October 19, 2018, Amendment No. 5, dated March 11, 2019, Amendment No. 6, dated May 22, 2019, Amendment No. 7, dated December 18, 2019 and the Incremental Amendment and Joinder Agreement, dated August 17, 2020 (the “Term Loan Facility”). Pursuant to Amendment No. 7, the Borrower borrowed approximately $418.0 million aggregate principal amount of loans (the “December 2019 Refinancing Loans”). Pursuant to Amendment No. 5, the Borrower received $200.0 million aggregate principal amount of revolving commitments, which was increased to $275.0 million aggregate amount of revolving commitments (the “Incremental Revolving Commitments”) pursuant to the Incremental Amendment and Joinder Agreement. The Incremental Revolving Commitments were established pursuant to an incremental facility (the “Revolving Credit Facility”) and includes a $50.0 million letter of credit sub-facility. The Incremental Revolving Commitments will terminate in March 2024. Borrowings under the Revolving Credit Facility are available for general corporate purposes. As of June 30, 2021, the Revolving Credit Facility was undrawn. As used herein, all references to the “Credit Agreement” are references to the original credit agreement, dated as of May 7, 2015, as amended through the March 2021 Amendment. The Incremental Loans were incurred as a separate class of term loans under the Credit Agreement with substantially the same terms of the December 2019 Refinancing Loans. The Borrower used the proceeds of the Incremental Loans to fund a portion of the consideration payable in the acquisition of Viela. The Incremental Loans bear interest at a rate, at Borrower’s option, equal to the London Inter-Bank Offered Rate (“LIBOR”), plus 2.00% per annum (subject to a 0.50% LIBOR floor) or the adjusted base rate plus 1.00% per annum, with a step-down to LIBOR plus 1.75% per annum or the adjusted base rate plus 0.75% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00. The adjusted base rate is defined as the greatest of (a) LIBOR (using one-month interest period) plus 1.00%, (b) the prime rate, (c) the federal funds rate plus 0.50%, and (d) 1.00%. The December 2019 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 May 22, 2019 (the “Refinanced Loans”) to effectuate a repricing of the Refinanced Loans. The Borrower used the proceeds of the December 2019 Refinancing Loans to repay the Refinanced Loans, which totaled approximately $418.0 million. The December 2019 Refinancing Loans bear interest at a rate, at the Borrower’s option, equal to LIBOR plus 2.25% per annum (subject to a 0.00% LIBOR floor) or the adjusted base rate plus 1.25% per annum, with a step-down to LIBOR plus 2.00% per annum or the adjusted base rate plus 1.00% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00. The loans under the Revolving Credit Facility bear interest, at the Borrower’s option, at a rate equal to either LIBOR plus an applicable margin of 2.25% per annum (subject to a LIBOR floor of 0.00%), or the adjusted base rate plus 1.25% per annum, with a step-down to LIBOR plus 2.00% per annum or the adjusted base rate plus 1.00% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00. The Credit Agreement provides for (i) the Incremental Loans, (ii) the December 2019 Refinancing Loans, (iii) the Revolving Credit Facility, (iv) one or more uncommitted additional incremental loan facilities subject to the satisfaction of certain financial and other conditions, and (v) 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 additional borrowers under incremental or refinancing facilities. The obligations under the Credit Agreement (including obligations in respect of the Incremental Loans, December 2019 Refinancing Loans and the Revolving Credit Facility) and any swap obligations and cash management obligations owing to a lender (or an affiliate of a lender) 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 Incremental Loans, December 2019 Refinancing Loans and the Revolving Credit Facility) and any related 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 Borrower and the guarantors, except for certain customary excluded assets, and (ii) all of the capital stock owned by the Borrower and guarantors thereunder (limited, in the case of the stock of certain non-U.S. subsidiaries of the Borrower, to 65% of the capital stock of such subsidiaries). The Borrower and the guarantors under the Credit Agreement are individually and collectively referred to herein as a “Loan Party” and the “Loan Parties,” as applicable. The Borrower is 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 Incremental Loans, a 1% premium will apply to a repayment of the Incremental 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 September 15, 2021 The Incremental Loans will amortize in equal quarterly installments in an aggregate annual amount equal to 1% of the original principal amount thereof, with any remaining balance payable on March 15, 2028, the final maturity date of the Incremental Loans. December 2019 Refinancing Loans is due and 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. The Credit Agreement also contains a springing financial maintenance covenant, which requires that the Company maintain a specified leverage ratio at the end of each fiscal quarter. The covenant is tested if both the outstanding loans and letters of credit under the Revolving Credit Facility, subject to certain exceptions, exceed 25% of the total commitments under the Revolving Credit Facility as of the last day of any fiscal quarter. If the Company fails to meet this covenant, the commitments under the Revolving Credit Facility could be terminated and any outstanding borrowings, together with accrued interest, under the Revolving Credit Facility could be declared immediately due and payable. Other events of default under the Credit Agreement include: (i) the failure by the 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 Credit Agreement to be immediately due and payable. The interest on the Incremental Loans is variable and, as of June 30, 2021 the interest rate on the Incremental Loans was 2.50% and the effective interest rate was 2.75%. The interest on the December 2019 Refinancing Loans is variable and as of June 30, 2021 the interest rate on the December 2019 Refinancing Loans was 2.38% and the effective interest rate was 2.67%. As of June 30, 2021, the fair value of the amounts outstanding under the Incremental Loans and the December 2019 Refinancing Loans were approximately $1,586.0 million and $414.9 million, respectively, categorized as a Level 2 instrument, as defined in Note 12. 2027 Senior Notes On July 16, 2019, HTUSA completed a private placement of $600.0 million aggregate principal amount of 5.5% Senior Notes due 2027 (the “2027 Senior Notes”) to several investment banks acting as initial purchasers, who subsequently resold the 2027 Senior Notes to persons reasonably believed to be qualified institutional buyers. The Company used the net proceeds from the offering of the 2027 Senior Notes, together with approximately $65.0 million in cash on hand, to redeem or prepay $625.0 million of its outstanding debt, consisting of (i) the outstanding $225.0 million principal amount of its 6.625 (ii) the outstanding $300.0 million principal amount of its 8.750 and (iii) $100.0 million of the outstanding principal amount of senior secured term loans under the Credit Agreement, as well as to pay the related premiums and fees and expenses, excluding accrued interest, associated with such redemption and prepayment. The 2027 Senior Notes are HTUSA’s general unsecured senior obligations, rank equally in right of payment with all existing and future senior debt of HTUSA and rank senior in right of payment to any existing and future subordinated debt of HTUSA. The 2027 Senior Notes are effectively subordinate to all of the existing and future secured debt of HTUSA to the extent of the value of the collateral securing such debt. The 2027 Senior Notes are unconditionally guaranteed on a senior basis by the Company and all of the Company’s restricted subsidiaries, other than HTUSA and certain immaterial subsidiaries, that guarantee the Credit Agreement. The guarantees are each guarantor’s senior unsecured obligations and rank equally in right of payment with such guarantor’s existing and future senior debt and senior in right of payment to any existing and future subordinated debt of such guarantor. The guarantees are effectively subordinated to all of the existing and future secured debt of each guarantor, including such guarantor’s guarantee under the Credit Agreement, to the extent of the value of the collateral securing such debt. The guarantees of a guarantor may be released under certain circumstances. The 2027 Senior Notes are structurally subordinated to all of the liabilities of the Company’s subsidiaries that do not guarantee the 2027 Senior Notes. The 2027 Senior Notes accrue interest at an annual rate of 5.5% payable semiannually in arrears on February 1 and August 1 of each year, beginning on February 1, 2020. The 2027 Senior Notes will mature on August 1, 2027, unless earlier exchanged, repurchased or redeemed. Except as described below, the 2027 Senior Notes may not be redeemed before August 1, 2022. Thereafter, some or all of the 2027 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 August 1, 2022, some or all of the 2027 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 August 1, 2022, up to 40% of the aggregate principal amount of the 2027 Senior Notes may be redeemed at a redemption price of 105.5% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings. In addition, the 2027 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 2027 Senior Notes, HTUSA 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, HTUSA will be required to make an offer to purchase all of the 2027 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, subject to certain exceptions. If the Company or certain of its subsidiaries engages in certain asset sales, HTUSA will be required under certain circumstances to make an offer to purchase the 2027 Senior Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the repurchase date. The indenture governing the 2027 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 2027 Senior Notes receive investment grade ratings. The indenture governing the 2027 Senior Notes also includes customary events of default. As of June 30, 2021, the interest rate on the 2027 Senior Notes was 5.50% and the effective interest rate was 5.76%. As of June 30, 2021, the fair value of the 2027 Senior Notes was approximately $636.0 million, categorized as a Level 2 instrument, as defined in Note 12.

Lease Obligations

Lease Obligations	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Lease Obligations	NOTE 14 – LEASE OBLIGATIONS As of June 30, 2021, the Company had the following office space lease agreements in place for real properties: Location Approximate Square Feet Lease Expiry Date Dublin, Ireland (St. Stephen’s Green) (1) 63,000 May 4, 2041 Dublin, Ireland (Connaught House) (1) 18,900 November 4, 2029 Lake Forest, Illinois 160,000 March 31, 2031 Novato, California 61,000 August 31, 2021 South San Francisco, California 20,000 January 31, 2030 Rockville, Maryland (2) 24,500 August 31, 2023 to April 30, 2026 Chicago, Illinois 9,200 December 31, 2028 Gaithersburg, Maryland (2) 7,200 June 30, 2022 Washington, D.C. 6,000 September 15, 2022 Mannheim, Germany 4,800 December 31, 2022 (1) In October 2019, the Company entered into an agreement for lease relating to approximately 63,000 square feet of office space under construction in Dublin, Ireland. In May 2021, the construction of the office was completed by the lessor and the lease became effective. As a result, the Company recognized $60.9 million as a right-of-use asset and a corresponding lease liability on the condensed consolidated balance sheet. The lease is due to expire in May 2041. The Company expects to incur leasehold improvement costs during 2021 in order to prepare the building for occupancy. The Company plans to move its Connaught House office employees to the St. Stephen’s Green office in the fourth quarter of 2021. In July 2021, the Company entered into an agreement to assign the Connaught House lease to a third party and the lease assignment will become effective in the fourth quarter of 2021. (2) On March 15, 2021, the Company completed its acquisition of Viela. As part of the acquisition, the Company assumed two leases in Rockville, Maryland for both office and laboratory space and a lease in Gaithersburg, Maryland for office space. On March 18, 2021, the Company entered into a third lease in Rockville, Maryland for office and laboratory space, with a lease commencement date of April 1, 2021. As of June 30, 2021 and December 31, 2020, the Company had right-of-use lease assets included in other assets of $85.1 million and $34.4 million, respectively; current lease liabilities included in accrued expenses and other current liabilities of $4.6 million and $4.1 million, respectively; and non-current lease liabilities included in other long-term liabilities of $103.5 million and $43.2 million, respectively, in its condensed consolidated balance sheets. In February 2021, the Company vacated the Lake Forest leased office building. As a result of the Company vacating the Lake Forest office, the Company recorded an impairment charge of $12.4 million during the six months ended June 30, 2021, using an income approach based on market prices for similar properties provided by a third-party. This charge was reported within impairment of long-lived assets in the condensed consolidated statement of comprehensive income (loss). The Company recognizes rent expense on a monthly basis over the lease term based on a straight-line method. Rent expense was $2.4 million and $1.8 million for the three months ended June 30, 2021 and 2020, respectively, and $4.0 million and $3.4 million for the six months ended June 30, 2021 and 2020, respectively. The table below reconciles the undiscounted cash flows for each of the first five years and total of the remaining years to the lease liabilities recorded on the Company’s condensed consolidated balance sheet as of June 30, 2021 (in thousands): 2021 (July to December) $ 3,937 2022 7,356 2023 11,030 2024 11,855 2025 11,840 Thereafter 102,726 Total lease payments 148,744 Imputed interest (40,696 ) Total lease liabilities $ 108,048 The weighted-average discount rate and remaining lease term for leases as of June 30, 2021 was 4.88% and 15.06 years, respectively.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 15 – COMMITMENTS AND CONTINGENCIES Purchase Commitments Under the Company’s supply agreement with AGC Biologics A/S (formerly known as CMC Biologics A/S) (“AGC Biologics”), the Company has agreed to purchase certain minimum annual order quantities of TEPEZZA drug substance. In addition, the Company must provide AGC Biologics with rolling forecasts of TEPEZZA drug substance requirements, with a portion of the forecast being a firm and binding order. At June 30, 2021, the Company had binding purchase commitments with AGC Biologics for TEPEZZA drug substance of €143.9 million ($170.6 million converted at a Euro-to-Dollar exchange rate as of June 30, 2021 of 1.1858), to be delivered through December 2023. Under the Company’s supply agreement with Catalent Indiana, LLC (“Catalent”), the Company must provide Catalent with rolling forecasts of TEPEZZA drug product requirements, with a portion of the forecast being a firm and binding order. At June 30, 2021, the Company had binding purchase commitments with Catalent for TEPEZZA drug product of $10.2 million, to be delivered through June 2022. On December 17, 2020, the Company announced that it expected a short-term disruption in TEPEZZA supply as a result of U.S. government-mandated COVID-19 vaccine production orders pursuant to the Defense Production Act of 1950 (“DPA”) that dramatically restricted capacity available for the production of TEPEZZA at its drug product contract manufacturer, Catalent. Pursuant to the DPA, Catalent was ordered to prioritize certain COVID-19 vaccine manufacturing at Catalent, resulting in the cancellation of previously guaranteed and contracted TEPEZZA drug product manufacturing slots in December 2020, which were required to maintain TEPEZZA supply. To offset the reduced slots allowed by the DPA and Catalent, the Company accelerated plans to increase the production scale of TEPEZZA drug product. In March 2021, the FDA approved a prior approval supplement to the TEPEZZA Biologics License Application (which was previously approved in January 2020), giving the Company authorization to manufacture more TEPEZZA drug product resulting in an increased number of vials with each manufacturing slot. The Company commenced resupply of TEPEZZA to the market in April 2021. Under the Company’s agreement with Bio-Technology General (Israel) Ltd (“BTG Israel”), the Company has agreed to purchase certain minimum annual order quantities and is obligated to purchase at least 80 percent of its annual world-wide bulk product requirements for KRYSTEXXA from BTG Israel. The term of the agreement runs until December 31, 2030, and will automatically renew for successive three-year f the manufacture of the is moved out of Israel, the Company may be required to obtain the approval of the Israel Innovation Authority (formerly known as Israeli Office of the Chief Scientist) (“IIA”) because certain KRYSTEXXA intellectual property was initially developed with a grant funded by the IIA. Under an agreement with Boehringer Ingelheim Biopharmaceuticals GmbH (“Boehringer Ingelheim Biopharmaceuticals”), Boehringer Ingelheim Biopharmaceuticals is required to manufacture and supply ACTIMMUNE and IMUKIN to the Company. Following the Company’s sale of the rights to IMUKIN in all territories outside of the United States, Canada and Japan to Clinigen Group plc (“Clinigen”), purchases of IMUKIN inventory are being resold to Clinigen. 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. As of June 30, 2021, the minimum purchase commitment to Boehringer Ingelheim Biopharmaceuticals was $15.2 million (converted using a Euro-to-Dollar exchange rate of 1.1858 as of June 30, 2021) through June 2024. Excluding the above, additional purchase orders and other commitments relating to the manufacture of RAVICTI, BUPHENYL, PROCYSBI, PENNSAID 2%, DUEXIS, RAYOS, QUINSAIR and UPLIZNA of $18.7 million were outstanding at June 30, 2021. 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 assistance 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 may 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 assistance programs and sales and marketing activities may result in damages, fines, penalties or other administrative sanctions against the Company. On March 5, 2019, the Company received a civil investigative demand (“CID”) from the United States Department of Justice (“DOJ”) pursuant to the Federal False Claims Act regarding assertions that certain of the Company’s payments to pharmacy benefit managers (“PBMs”) were potentially in violation of the Anti-Kickback Statute. The CID requests certain documents and information related to the Company’s payments to PBMs, pricing and the Company’s patient assistance program regarding DUEXIS, VIMOVO and PENNSAID 2%. The Company is cooperating with the investigation. While the Company believes that its payments and programs are compliant with the Anti-Kickback Statute, no assurance can be given as to the timing or outcome of the DOJ’s investigation, or that it will not result in a material adverse effect on the Company’s business. Royalty and Milestone Agreements TEPEZZA Under the acquisition agreement for River Vision, the Company agreed to pay up to $325.0 million upon the attainment of various milestones, composed of $100.0 million related to FDA approval and $225.0 million related to net sales thresholds for TEPEZZA. The Company made the $100.0 million milestone payment related to FDA approval during the first quarter of 2020. The aggregate potential milestone payments of $225.0 million were payable based on certain TEPEZZA worldwide net sales thresholds being achieved as noted in the following table: TEPEZZA Worldwide Net Sales Threshold Milestone Payment >$250 million $50 million >$375 million $75 million >$500 million $100 million The agreement also includes a royalty payment of 3 percent of the portion of annual worldwide net sales exceeding $300.0 million. S.R. One and Lundbeckfond, as two of the former River Vision stockholders, both held rights to receive approximately 35.66% of any future TEPEZZA payments. As a result of the Company’s agreements with S.R. One and Lundbeckfond in April 2020, the Company’s remaining net obligations to make TEPEZZA sales-based milestone and royalty payments to the former stockholders of River Vision was reduced by approximately 70.25%, after including payments to a third party. Under the Company’s license agreement with Roche, the Company is required to pay Roche up to CHF103.0 million upon the attainment of various development, regulatory and sales milestones for TEPEZZA. The Company made a milestone payment of CHF5.0 million ($5.2 million when converted using a CHF-to-Dollar exchange rate at the date of payment of 1.0382) related to FDA approval during the first quarter of 2020. The agreement with Roche also includes tiered royalties on annual worldwide net sales between 9 and 12 percent. The Company’s remaining obligation to Roche relating to the attainment of various TEPEZZA development and regulatory milestones is CHF43.0 million ($46.5 million when converted using a CHF-to-Dollar exchange rate at June 30, 2021 of 1.0813). Under the Company’s license agreement with Lundquist Institute (formerly known as Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center) (“Lundquist”), the Company is required to pay Lundquist a royalty payment of less than 1 percent of TEPEZZA net sales. The royalty terminates upon Under the Company’s license agreement with Boehringer Ingelheim Biopharmaceuticals, the Company is required to pay Boehringer Ingelheim Biopharmaceuticals milestone payments totaling less than $2.0 million upon the achievement of certain TEPEZZA sales milestones. License Agreements On June 18, 2021, the Company entered into a global agreement with Arrowhead for ARO-XDH, a previously undisclosed discovery-stage investigational RNAi therapeutic being developed by Arrowhead as a potential treatment for uncontrolled gout. Arrowhead granted the Company a worldwide exclusive license to develop, manufacture and commercialize the RNAi therapeutic products. Arrowhead will conduct all research and preclinical development activities for the RNAi therapeutic products. The Company must use commercially reasonable efforts in, and will be responsible for, clinical development and commercialization of the RNAi therapeutic products. On November 21, 2020, the Company entered into a global agreement with Halozyme that gives the Company exclusive access to Halozyme’s ENHANZE drug delivery technology for SC formulation of medicines targeting IGF-1R. The Company intends to use ENHANZE to develop a SC formulation of TEPEZZA. Under the terms of the agreement, the Company paid Halozyme an upfront cash payment of $30.0 million in December 2020 and agreed to pay additional potential future milestone payments of up to $160.0 million contingent on the satisfaction of certain development and sales thresholds. Other Agreements On April 1, 2020, the Company acquired Curzion for an upfront payment of $45.0 million with additional payments of up to $15.0 million contingent on the achievement of certain development and regulatory milestones. Under separate agreements with two additional parties, the Company is also required to make contingent payments upon the achievement of certain development and regulatory milestones and certain net sales thresholds. These separate agreements also include mid to high-single-digit royalty payments based on the portion of annual worldwide net sales. During the year ended December 31, 2020, the Company committed to invest as a strategic limited partner in four venture capital funds: Forbion Growth Opportunities Fund I C.V., Forbion Capital Fund V C.V., Aisling Capital V, L.P. and RiverVest Venture Fund V, L.P. As of June 30, 2021, the total carrying amount of the Company’s investments in these funds was $20.2 million, which is included in other assets in the condensed consolidated balance sheet, and includes $7.6 million in net cash payments for investments made during the first half of 2021. As of June 30, 2021, the Company’s total future commitments to these funds were $48.1 million. During the six months ended June 30, 2021, the Company recorded investment income under the equity method of $1.7 million in the other (expense) income, net line item of the Company’s consolidated statement of comprehensive income (loss) related to these funds. As of June 30, 2021, the Company had $10.7 million of non-cancellable advertising commitments due within one year, primarily related to agreements for advertising for TEPEZZA and KRYSTEXXA. 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. 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. 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 HTUSA.

Legal Proceedings

Legal Proceedings	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Legal Proceedings	NOTE 16 - LEGAL PROCEEDINGS DUEXIS On May 29, 2018, the Company received notice from Alkem Laboratories, Inc. (“Alkem”) that it had filed an Abbreviated New Drug Application (“ANDA”) with the FDA seeking approval of a generic version of DUEXIS. The ANDA contained a Paragraph IV Patent Certification alleging that the patents covering DUEXIS are invalid and/or will not be infringed by Alkem’s manufacture, use or sale of the medicine for which the ANDA was submitted. The Company filed suit in the United States District Court of Delaware against Alkem on July 9, 2018, seeking an injunction to prevent the approval of Alkem’s ANDA and/or to prevent Alkem from selling a generic version of DUEXIS. The litigation went to trial on September 14, 2020. On November 30, 2020, the District Court issued an adverse judgment against the Company, invalidating U.S Patent No. 8,607,033 and finding that Alkem’s generic product would not infringe the ‘033 patent. And following an adverse claim construction ruling, the District Court entered a judgment that the Alkem generic product would not infringe U.S. Patent No. 8,607,451, subject to the Company’s right to appeal the District Court’s claim construction ruling. On December 23, 2020, the Company initiated an appeal of the adverse judgments on the ‘033 and ‘451 patents with the Federal Circuit Court of Appeals. On September 26, 2018, the Company received notice from Teva Pharmaceuticals USA, Inc. (“Teva USA”) that it had filed an ANDA with the FDA seeking approval of a generic version of DUEXIS. The ANDA contained a Paragraph IV Patent Certification alleging that the patents covering DUEXIS are invalid and/or will not be infringed by Teva USA’s manufacture, use or sale of the medicine for which the ANDA was submitted. The Company filed suit in the United States District Court of New Jersey against Teva USA on July 2, 2020, seeking to prevent Teva USA from selling a generic version of DUEXIS. The parties are currently engaged in discovery. The court has not yet set a trial date. On May 24, 2021, the Company received notice from Torrent Pharmaceuticals Limited (“Torrent”) that it had filed an ANDA with the FDA seeking approval of a generic version of DUEXIS. The ANDA contained a Paragraph IV Patent Certification alleging that the patents covering DUEXIS are invalid and/or will not be infringed by Torrent’s manufacture, use or sale of the medicine for which the ANDA was submitted. The Company filed suit in the United States District Court of New Jersey against Torrent on July 7, 2021, seeking to prevent Torrent from selling a generic version of DUEXIS. VIMOVO On February 18, 2020, the FDA granted final approval for Dr. Reddy’s Laboratories Inc. and Dr. Reddy’s Laboratories Ltd. (collectively, “Dr. Reddy’s”) generic version of VIMOVO. On February 27, 2020, Dr. Reddy’s launched its generic version of VIMOVO in the United States, and the Company now faces generic competition with respect to VIMOVO. The Company continues to assert claims of infringement against Dr. Reddy’s based on U.S. Patent No. 8,858,996 and U.S. Patent No. 9,161,920 in the District Court for the District of New Jersey. PROCYSBI On June 27, 2020, the Company received notice from Lupin Limited (“Lupin”) that it had filed an ANDA with the FDA seeking approval of a generic version of PROCYSBI. The ANDA contained a Paragraph IV Patent Certification alleging that the patents covering PROCYSBI are invalid and/or will not be infringed by Lupin’s manufacture, use or sale of the medicine for which the ANDA was submitted. The Company filed suit in the United States District Court of New Jersey against Lupin on August 11, 2020, seeking to prevent Lupin from selling a generic version of PROCYSBI.

Share-Based and Long-Term Incen

Share-Based and Long-Term Incentive Plans	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based and Long-Term Incentive Plans	NOTE 17 – SHARE-BASED AND LONG-TERM INCENTIVE PLANS The Company’s equity incentive plans at June 30, 2021 included its 2011 Equity Incentive Plan, as amended, 2014 Employee Share Purchase Plan, as amended, Amended and Restated 2014 Equity Incentive Plan (“2014 EIP”), 2014 Non-Employee Equity Plan, as amended (“2014 Non-Employee Plan”), 2020 Employee Share Purchase Plan (“2020 ESPP”), Amended and Restated 2020 Equity Incentive Plan (“2020 EIP”) and Amended and Restated 2018 Equity Incentive Plan (“2018 EIP”). On February 17, 2021, the Compensation Committee of the Company’s Board of Directors (the “Compensation Committee”) approved amending the 2020 EIP, subject to shareholder approval, including increasing the number of ordinary shares available for the grant of equity awards to the Company’s employees by an additional 7,000,000 shares. On April 29, 2021, the shareholders of the Company approved such amendment to the 2020 EIP. As of June 30, 2021, an aggregate of 2,519,726 ordinary shares were authorized and available for future issuance under the 2020 ESPP, an aggregate of 15,929,053 ordinary shares were authorized and available for future grants under the 2020 EIP, an aggregate of 526,895 ordinary shares were authorized and available for future grants under the 2014 Non-Employee Plan and an aggregate of 2,328,059 ordinary shares were authorized and available for future grants under the 2018 EIP. Stock Options The following table summarizes stock option activity during the six months ended June 30, 2021: Options Weighted Average Exercise Price Weighted Average Contractual Term Remaining (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2020 7,129,615 $ 21.24 4.60 $ 370,073 Assumed in acquisition (1) 1,318,053 41.23 — — Exercised (993,945 ) 28.11 — — Forfeited (58,301 ) 45.06 — — Expired (234 ) 17.31 — — Outstanding as of June 30, 2021 7,395,188 23.69 4.47 517,258 Exercisable as of June 30, 2021 6,602,752 $ 21.67 4.04 $ 475,154 Stock options typically have a contractual term of ten years from grant date. (1) On March 15, 2021, the Company completed its acquisition of Viela. Under the terms of the merger agreement for Viela, all outstanding Viela stock options assumed by the Company with vesting dates after June 1, 2021, were converted into stock options to purchase the Company’s ordinary shares. As of March 15, 2021, options previously exercisable for an aggregate of 2,180,159 shares of Viela’s common stock that were converted at a rate of 0.60 to 1 based on the merger agreement, into options to purchase 1,318,053 of the Company’s ordinary shares, were outstanding. Restricted Stock Units The following table summarizes restricted stock unit activity for the six months ended June 30, 2021: Number of Units Weighted Average Grant-Date Fair Value Per Unit Outstanding as of December 31, 2020 5,909,120 $ 27.87 Granted 1,991,241 75.12 Vested (2,758,014 ) 23.36 Forfeited (235,032 ) 59.93 Outstanding as of June 30, 2021 4,907,315 $ 48.10 The grant-date fair value of restricted stock units is the closing price of the Company’s ordinary shares on the date of grant. Performance Stock Unit Awards The following table summarizes performance stock unit awards (“PSUs”) activity for the six months ended June 30, 2021: Number of Units Weighted Average Grant-Date Fair Value Per Unit Average Illiquidity Discount Recorded Weighted Average Fair Value Per Unit Outstanding as of December 31, 2020 2,610,924 Granted 450,577 $ 93.73 8.64 % $ 85.64 Forfeited (24,450 ) 93.73 9.21 % 85.10 Vested (2,021,657 ) 21.21 2.66 % 20.65 Performance Based Adjustment (1) 512,819 25.42 7.27 % 23.57 Outstanding as of June 30, 2021 1,528,213 (1) Represents adjustment based on the net sales performance criteria meeting 162.5% of target as of December 31, 2020 for the 2020 PSUs (as defined below), the net sales performance criteria meeting 200.0% of target as of December 31, 2020 for the TEPEZZA PSUs (as defined below) and meeting total shareholder return (“TSR”) performance at 200.0% for the PSUs that were awarded to key executive participants on January 5, 2018. On January 4, 2021, the Company awarded PSUs to key executive participants (“2021 PSUs”). The 2021 PSUs utilize three long-term performance metrics: a component tied to technical operations milestones for the Company over the next two years, a component tied to research and development milestones for the Company over the next three years and a component tied to relative three-year compounded annual TSR as follows: • 50% of the granted 2021 PSUs that may vest (such portion of the PSU award, the “2021 Relative TSR PSUs”) are determined by reference to the level of the Company’s relative TSR over the three-year • 25% of the 2021 PSUs that may vest (such portion of the PSU award, the “2021 Tech Ops PSUs”) are determined by reference to the Company’s achievement of certain performance objectives related to technical operations. • 25% of the 2021 PSUs that may vest (such portion of the PSU award, the “2021 R&D PSUs”) are determined by reference to the Company’s achievement of certain performance objectives related to research and development. On January 3, 2020, the Company awarded PSUs to key executive participants (“2020 PSUs”). The 2020 PSUs utilize two performance metrics: a short-term component tied to business performance and a long-term component tied to relative compounded annual TSR, as follows: • 30% of the granted 2020 PSUs that may vest (such portion of the PSU award, the “2020 Relative TSR PSUs”) are determined by reference to the level of the Company’s relative TSR over the three-year • 70% of the 2020 PSUs that may vest (such portion of the PSU award, the “2020 Net Sales PSUs”) are determined by reference to the Company’s net sales for certain components of its orphan segment. As a result of the impact of the COVID-19 pandemic on certain aspects of the Company’s business in 2020, the performance goals associated with certain of the Company’s performance-based equity awards no longer reflected the Company’s expectations, causing the awards to lose their incentive to employees. Accordingly, on July 28, 2020 the Compensation Committee approved a modification to 57% of the 2020 Net Sales PSUs awarded on January 3, 2020 that were to vest based on KRYSTEXXA 2020 net sales. Those 2020 Net Sales PSUs related to KRYSTEXXA may now be earned based on net sales of KRYSTEXXA achieved by the end of a modified 18-month performance period that ended on July 1, 2021 instead of a 12-month performance period ending December 31, 2020. As a result, the first one-third of any 2020 PSUs earned vested on July 1, 2021 and the vesting of the remaining two-thirds is unchanged and will vest one-third each on January 5, 2022 and on January 5, 2023. There were 12 participants impacted by the modification. The total compensation cost resulting from the modification was approximately $12.0 million and is being recognized over the remaining requisite service period. All PSUs outstanding at June 30, 2021 may vest in a range of between 0% and 200%, with the exception of the modified KRYSTEXXA 2020 Net Sales PSUs which are capped at 150%, based on the performance metrics described above. The Company accounts for the 2020 PSUs and 2021 PSUs as equity-settled awards in accordance with ASC 718, Compensation-Stock Compensation Valuation date stock price $ 72.54 Expected volatility 45.8 % Risk free rate 0.2 % The value of the 2020 Net Sales PSUs related to KRYSTEXXA and 2021 Tech Ops PSUs and 2021 R&D PSUs is calculated at the end of each quarter based on the expected payout percentage based on estimated full-period performance against targets, and the Company adjusts the expense quarterly. On January 4, 2019, the Company awarded a company-wide grant of PSUs (the “TEPEZZA PSUs”). Vesting of the TEPEZZA PSUs was contingent upon receiving shareholder approval of amendments to the 2014 EIP, which approval was received on May 2, 2019. The TEPEZZA PSUs were generally eligible to vest contingent upon receiving approval of the TEPEZZA biologics license application Share-Based Compensation Expense The following table summarizes share-based compensation expense included in the Company’s condensed consolidated statements of operations for the six months ended June 30, 2021 and 2020 (in thousands): For the Six Months Ended June 30, 2021 2020 Share-based compensation expense Cost of goods sold $ 5,080 $ 3,977 Research and development 17,776 8,928 Selling, general and administrative 92,734 70,573 Total share-based compensation expense $ 115,590 $ 83,478 During the six months ended June 30, 2021 and 2020, the Company recognized $60.9 million and $19.3 million of tax benefit, respectively, related to share-based compensation resulting primarily from the fair value of equity awards at the time of the exercise of stock options and vesting of restricted stock units and PSUs. As of June 30, 2021, the Company estimates that pre-tax unrecognized compensation expense of $294.2 million for all unvested share-based awards, including stock options, restricted stock units and PSUs, will be recognized through the second quarter of 2023. 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 2020 EIP and the 2018 EIP.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 18 – 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 valuation allowances 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. 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. The impact of tax rate changes on deferred tax assets and liabilities is recognized in the period in which the change is enacted. The following table presents the (benefit) expense for income taxes for the three and six months ended June 30, 2021 and 2020 (in thousands): For June 30, For June 30, 2021 2020 2021 2020 Income (loss) before (benefit) expense for income taxes $ 115,633 $ 2,954 $ (55,469 ) $ (29,663 ) (Benefit) expense for income taxes (42,484 ) 82,964 (90,235 ) 63,938 Net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 ) During the three and six months ended June 30, 2021, the Company recorded a benefit for income taxes of $42.5 million and $90.2 million, respectively. During the three and six months ended June 30, 2020, the Company recorded an expense for income taxes of $83.0 million and $63.9 million, respectively. The increase in benefit for income taxes recorded during the three and six months ended June 30, 2021 compared to the three and six months ended June 30, 2020, resulted primarily from the mix of pre-tax income and losses incurred in various tax jurisdictions, an increase in the tax benefits recognized on share-based compensation and the recognition of a deferred tax asset resulting from an intercompany transfer and license of intellectual property from a U.S. subsidiary to an Irish subsidiary during the three and six months ended June 30, 2021. These increases in benefit were partially offset by tax expense recognized on U.S. taxable income generated from the intercompany transfer and license of intellectual property. During the three and six months ended June 30, 2020, we recorded a $15.2 million provision following the publication, on April 8, 2020, by the U.S. Department of the Treasury, of Final Regulations for Section 267A. The Final Regulations for Section 267A permanently disallow for U.S. tax purposes certain interest expense accrued to a foreign related party during the year ended December 31, 2019. As a result, we recorded a write off of a deferred tax asset related to this interest expense during the three and six months ended June 30, 2020 and recognized a corresponding tax provision of $15.2 million. There was no similar provision recorded during the three and six months ended June 30, 2021.

Subsequent Event

Subsequent Event	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Event	NOTE 19 – SUBSEQUENT EVENT In July 2021

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Unless otherwise indicated or the context otherwise requires, references to “Horizon”, the “Company”, “we”, “us” and “our” refer to Horizon Therapeutics plc and its consolidated subsidiaries. On March 15, 2021, the Company completed its acquisition of Viela Bio, Inc. (“Viela”) and acquired all of the issued and outstanding shares of Viela’s common stock for $53.00 per share. The total consideration for the acquisition was approximately $3.0 billion, including cash acquired of $342.3 million. Following the completion of the acquisition, Viela became a wholly-owned subsidiary of the Company. The unaudited condensed consolidated financial statements presented herein include the results of operations of the acquired business from the date of acquisition. The unaudited condensed consolidated financial statements presented herein have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, the financial statements do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, all adjustments, including normal recurring adjustments, considered necessary for a fair statement of the financial statements have been included. Operating results for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. The December 31, 2020 condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by GAAP.
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. In December 2019, the FASB issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplification and reduce the cost of accounting for income taxes Other recent authoritative guidance issued by the FASB (including technical corrections to the Accounting Standards Codification (“ASC”)), the American Institute of Certified Public Accountants and the Securities and Exchange Commission (“SEC”) did not, or are not expected to, have a material impact on the Company’s condensed consolidated financial statements and related disclosures.
Intangible Assets	Intangible Assets 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 intangibles, 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.

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Basic and Diluted Net Income (Loss) per Share	The following table presents basic and diluted net income (loss) per share for the three and six months ended June 30, 2021 and 2020 (in thousands, except share and per share data): For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Basic net income (loss) per share calculation: Numerator - net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 ) Denominator - weighted average ordinary shares outstanding 225,119,684 192,705,535 224,523,538 191,426,864 Basic net income (loss) per share $ 0.70 $ (0.42 ) $ 0.15 $ (0.49 ) For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Diluted net income (loss) per share calculation: Numerator - net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 ) Denominator - weighted average ordinary shares outstanding 235,191,860 192,705,535 234,719,830 191,426,864 Diluted net income (loss) per share $ 0.67 $ (0.42 ) $ 0.15 $ (0.49 )

Acquisitions, Divestitures an_2

Acquisitions, Divestitures and Other Arrangements (Tables)	6 Months Ended
	Jun. 30, 2021
Business Combinations [Abstract]
Schedule of Total Consideration for the Acquisitions	The total consideration for the acquisition was approximately $3.0 billion, including cash acquired of $342.3 million, and was composed of the following (in thousands): E quity value (54,988,820 shares at $53.00 per share) $ 2,914,407 Net settlements on the exercise of stock options 78,554 Consideration for exchange of Viela stock options 1,130 Total consideration $ 2,994,091
Schedule of Recognized Identified 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): Before Adjustments After Deferred tax liabilities, net $ (457,928 ) $ 6,869 $ (451,059 ) Accrued expenses and other current liabilities (73,401 ) (335 ) (73,736 ) Other long-term liabilities (22,631 ) — (22,631 ) Accounts payable (4,768 ) — (4,768 ) Accrued trade discounts and rebates (1,492 ) (373 ) (1,865 ) Marketable securities 400 — 400 Property, plant and equipment 1,747 — 1,747 Other assets 3,253 — 3,253 Accounts receivable 8,053 (267 ) 7,786 Prepaid expenses and other current assets 16,444 (837 ) 15,607 Inventories 149,348 2,300 151,648 Cash and cash equivalents 342,347 — 342,347 In-process research and development 910,000 — 910,000 Developed technology 1,460,000 — 1,460,000 (Liabilities assumed) and assets acquired 2,331,372 7,357 2,338,729 Goodwill 662,719 (7,357 ) 655,362 Fair value of consideration paid $ 2,994,091 $ — $ 2,994,091
Gain (Loss) on Sale of Assets	The following table presents the pro forma combined results of the Company and Viela for the six months ended June 30, 2021 and 2020 as if the acquisition of Viela had occurred on January 1, 2020: For the Six Months Ended June 30, 2021 2020 As reported Pro forma adjustments Pro forma As reported Pro forma adjustments Pro forma Net sales $ 1,174,954 $ 10,588 $ 1,185,542 $ 818,688 $ — $ 818,688 Net income (loss) 34,766 (30,804 ) 3,962 (93,601 ) (166,290 ) (259,891 )

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Components of Inventories	The components of inventories as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Raw materials $ 53,112 $ 11,760 Work-in-process 90,840 33,167 Finished goods 114,724 30,356 Inventories, net $ 258,676 $ 75,283

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Advance payments for inventory $ 134,716 $ 137,680 Deferred charge for taxes on intercompany profit 85,070 52,306 Prepaid income taxes and income tax receivable 63,609 102 Rabbi trust assets 23,885 18,423 Other prepaid expenses and other current assets 57,833 43,434 Prepaid expenses and other current assets $ 365,113 $ 251,945

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Buildings $ 128,266 $ 80,341 Land and land improvements 38,880 38,076 Construction in process 28,377 63,656 Machinery and equipment 16,669 4,695 Software 14,488 14,618 Furniture and fixtures 12,293 5,973 Leasehold improvements 9,847 26,323 Other 5,066 3,146 253,886 236,828 Less accumulated depreciation (33,744 ) (47,791 ) Property and equipment, net $ 220,142 $ 189,037

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Goodwill for Reportable Segments	The table below presents goodwill for the Company’s reportable segments as of June 30, 2021 (in thousands): Orphan Inflammation Total Balance at December 31, 2020 $ 357,498 $ 56,171 $ 413,669 Goodwill recognized on acquisition of Viela 662,719 — 662,719 Adjustment relating to the acquisition of Viela (7,357 ) — (7,357 ) Balance at June 30, 2021 $ 1,012,860 $ 56,171 $ 1,069,031
Amortizable Intangible Assets	Intangible assets as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Cost Accumulated Amortization Net Book Value Cost Basis Accumulated Amortization Net Book Value Developed technology $ 4,585,524 $ (1,468,423 ) $ 3,117,101 $ 3,093,886 $ (1,313,934 ) $ 1,779,952 In-process research and development (1) 880,000 — 880,000 — — — Customer relationships 8,100 (5,492 ) 2,608 8,100 (5,090 ) 3,010 Total intangible assets $ 5,473,624 $ (1,473,915 ) $ 3,999,709 $ 3,101,986 $ (1,319,024 ) $ 1,782,962
Estimated Future Amortization Expense	As of June 30, 2021, estimated future amortization expense was as follows (in thousands): 2021 (July to December) $ 179,397 2022 354,891 2023 354,376 2024 352,951 2025 350,700 Thereafter 1,527,394 Total $ 3,119,709

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilties (Tables)	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Payroll-related expenses $ 108,720 $ 121,577 Accrued royalties 68,104 68,006 Accrued upfront and milestone payments 46,500 123,442 Allowances for returns 37,881 40,918 R&D and manufacturing programs 36,992 17,289 Advertising and marketing 28,505 12,428 Consulting and professional services 25,310 21,893 Deferred revenues 20,835 — Pricing review liability 20,068 16,046 Accrued interest 15,688 14,207 Accrued other 69,896 49,761 Accrued expenses and other current liabilities $ 478,499 $ 485,567

Accrued Trade Discounts and R_2

Accrued Trade Discounts and Rebates (Tables)	6 Months Ended
	Jun. 30, 2021
Valuation And Qualifying Accounts Disclosure [Line Items]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Payroll-related expenses $ 108,720 $ 121,577 Accrued royalties 68,104 68,006 Accrued upfront and milestone payments 46,500 123,442 Allowances for returns 37,881 40,918 R&D and manufacturing programs 36,992 17,289 Advertising and marketing 28,505 12,428 Consulting and professional services 25,310 21,893 Deferred revenues 20,835 — Pricing review liability 20,068 16,046 Accrued interest 15,688 14,207 Accrued other 69,896 49,761 Accrued expenses and other current liabilities $ 478,499 $ 485,567
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued trade discounts and rebates as of , 2020 (in thousands): June 30, 2021 December 31, 2020 Accrued government rebates and chargebacks $ 191,663 $ 172,893 Accrued co-pay and other patient assistance 60,799 96,924 Accrued commercial rebates and wholesaler fees 53,902 82,646 Accrued trade discounts and rebates $ 306,364 $ 352,463 Invoiced commercial rebates and wholesaler fees, co-pay and other patient assistance costs, and government rebates and chargebacks in accounts payable 10,324 1,452 Total customer-related accruals and allowances $ 316,688 $ 353,915
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 from December 31, 2020 to June 30, 2021 (in thousands): Government Co-Pay and Wholesaler Fees Rebates and Other Patient and Commercial Chargebacks Assistance Rebates Total Balance at December 31, 2020 $ 172,893 $ 96,924 $ 84,098 $ 353,915 Current provisions relating to sales during the six months ended June 30, 2021 342,609 404,720 145,684 893,013 Adjustments relating to prior-year sales (9,376 ) (4,516 ) (2,361 ) (16,253 ) Payments relating to sales during the six months ended June 30, 2021 (171,269 ) (344,328 ) (83,411 ) (599,008 ) Payments relating to prior-year sales (144,605 ) (92,012 ) (79,854 ) (316,471 ) Viela acquisition on March 15, 2021 1,411 11 70 1,492 Balance at June 30, 2021 $ 191,663 $ 60,799 $ 64,226 $ 316,688

Segment and Other Information (

Segment and Other Information (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Summary of Net Sales by Medicine for Reportable Segments	The following table reflects net sales by medicine for the Company’s reportable segments for the three and six months ended June 30, 2021 and 2020 (in thousands): Three Months Ended June 30 Six Months Ended June 30 2021 2020 2021 2020 TEPEZZA $ 453,255 $ 165,936 $ 455,320 $ 189,387 KRYSTEXXA 130,317 75,201 237,074 168,450 RAVICTI 68,426 65,550 141,243 126,738 PROCYSBI 49,775 41,357 93,138 79,700 ACTIMMUNE 27,777 28,299 56,540 54,840 UPLIZNA 14,475 — 16,348 — BUPHENYL 2,262 2,846 3,922 5,160 QUINSAIR 222 59 431 336 Orphan segment net sales $ 746,509 $ 379,248 $ 1,004,016 $ 624,611 PENNSAID 2% 48,941 35,048 94,758 76,611 DUEXIS 22,110 27,798 41,575 59,145 RAYOS 13,406 14,459 28,678 32,668 VIMOVO 1,582 6,226 5,927 25,653 Inflammation segment net sales $ 86,039 $ 83,531 $ 170,938 $ 194,077 Total net sales $ 832,548 $ 462,779 $ 1,174,954 $ 818,688
Summary of Reconciliations of Segment Operating Income	The table below provides reconciliations of the Company’s segment operating income to the Company’s total income (loss) before expense for income taxes for the three and six months ended June 30, 2021 and 2020 (in thousands): For the Three Months Ended June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Segment operating income: Orphan $ 321,235 $ 151,541 $ 322,289 $ 205,897 Inflammation 46,767 38,096 89,447 90,038 Reconciling items: Amortization and step-up: Intangible amortization expense (88,523 ) (66,749 ) (154,892 ) (125,324 ) Inventory step-up expense (7,091 ) — (8,002 ) — Share-based compensation (54,424 ) (27,057 ) (115,590 ) (83,478 ) Upfront, progress and milestone payments related to license and collaboration agreements (46,500 ) (3,000 ) (49,500 ) (3,000 ) Acquisition/divestiture-related costs (30,626 ) (46,988 ) (80,017 ) (47,272 ) Interest expense, net (22,581 ) (18,571 ) (36,041 ) (35,915 ) Depreciation (3,393 ) (6,907 ) (7,844 ) (14,072 ) Restructuring and realignment costs (930 ) — (7,023 ) — Other (expense) income, net (262 ) 632 2,962 1,074 Fees related to refinancing activities — — — (54 ) Foreign exchange (loss) gain (39 ) 283 (887 ) 1,059 Loss on debt extinguishment — (17,254 ) — (17,254 ) Impairment of long-lived assets — (1,072 ) (12,371 ) (1,072 ) Drug substance harmonization costs — — — (290 ) Gain on sale of asset 2,000 — 2,000 — Income (loss) before (benefit) expense for income taxes $ 115,633 $ 2,954 $ (55,469 ) $ (29,663 )
Schedule of Gross Sales to Customers Included in Reportable Segments and All Other Customers as a Group	The following table presents the amount and percentage of gross sales to customers that represented more than 10% of the Company’s gross sales included in its two reportable segments and all other customers as a group for the three and six months ended June 30, 2021 and 2020 (in thousands, except percentages): For the Three Months Ended June 30, 2021 2020 Amount % of Amount % of Gross Sales Sales Customer A $ 410,436 31 % $ 314,288 35 % Customer B 342,148 26 % 194,576 22 % Customer C 240,290 18 % 160,814 18 % Customer D 212,820 16 % 112,676 13 % Other Customers 117,500 9 % 115,639 12 % Gross Sales $ 1,323,194 100 % $ 897,993 100 % For the Six Months Ended June 30, 2021 2020 Amount % of Amount % of Gross Sales Sales Customer A $ 659,176 32 % $ 561,063 33 % Customer B 526,835 25 % 401,853 24 % Customer C 358,327 17 % 294,689 17 % Customer D 303,439 15 % 197,464 12 % Other Customers 236,949 11 % 246,447 14 % Gross Sales $ 2,084,726 100 % $ 1,701,516 100 %
Summary of Net Sales Attributed to Geographic Sources	Geographic revenues are determined based on the country in which the Company’s customers are located. The following table presents a summary of net sales attributed to geographic sources for the three and six months ended June 30, 2021 and 2020 (in thousands, except percentages): Three Months Ended June 30, 2021 Three Months Ended June 30, 2020 Amount % of Total Net Sales Amount % of Total Net Sales United States $ 830,185 100% $ 460,827 100% Rest of world 2,363 * 1,952 * Net sales $ 832,548 $ 462,779 *Less than 1% Six Months Ended June 30, 2021 Six Months Ended June 30, 2020 Amount % of Total Net Sales Amount % of Total Net Sales United States $ 1,170,515 100% $ 814,843 100% Rest of world 4,439 * 3,845 * Net sales $ 1,174,954 $ 818,688 *Less than 1%

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Assets and Liabilities at Fair Value on Recurring Basis	The following tables set forth the Company’s financial assets and liabilities at fair value on a recurring basis as of June 30, 2021 and December 31, 2020 (in thousands): June 30, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 643,000 $ — $ — $ 643,000 Other current assets 23,885 — — 23,885 Total assets at fair value $ 666,885 $ — $ — $ 666,885 Liabilities: Other long-term liabilities (23,885 ) — — (23,885 ) Total liabilities at fair value $ (23,885 ) $ — $ — $ (23,885 ) December 31, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 1,906,000 — — $ 1,906,000 Other current assets 18,423 — — 18,423 Total assets at fair value $ 1,924,423 $ — $ — $ 1,924,423 Liabilities: Other long-term liabilities (18,423 ) — — (18,423 ) Total liabilities at fair value $ (18,423 ) $ — $ — $ (18,423 )

Debt Agreements (Tables)

Debt Agreements (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Outstanding Debt Balances	The Company’s outstanding debt balances as of June 30, 2021 and December 31, 2020 consisted of the following (in thousands): June 30, 2021 December 31, 2020 Term Loan Facility due 2028 $ 1,596,000 — Term Loan Facility due 2026 418,026 418,026 Senior Notes due 2027 600,000 600,000 Total face value 2,614,026 1,018,026 Debt discount (13,177 ) (10,061 ) Deferred financing fees (24,405 ) (4,586 ) Total long-term debt 2,576,444 1,003,379 Less: current maturities 16,000 — Long-term debt, net of current maturities $ 2,560,444 $ 1,003,379

Lease Obligations (Tables)

Lease Obligations (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of Office Space Lease Agreements in Place for Real Properties	As of June 30, 2021, the Company had the following office space lease agreements in place for real properties: Location Approximate Square Feet Lease Expiry Date Dublin, Ireland (St. Stephen’s Green) (1) 63,000 May 4, 2041 Dublin, Ireland (Connaught House) (1) 18,900 November 4, 2029 Lake Forest, Illinois 160,000 March 31, 2031 Novato, California 61,000 August 31, 2021 South San Francisco, California 20,000 January 31, 2030 Rockville, Maryland (2) 24,500 August 31, 2023 to April 30, 2026 Chicago, Illinois 9,200 December 31, 2028 Gaithersburg, Maryland (2) 7,200 June 30, 2022 Washington, D.C. 6,000 September 15, 2022 Mannheim, Germany 4,800 December 31, 2022 (1) In October 2019, the Company entered into an agreement for lease relating to approximately 63,000 square feet of office space under construction in Dublin, Ireland. In May 2021, the construction of the office was completed by the lessor and the lease became effective. As a result, the Company recognized $60.9 million as a right-of-use asset and a corresponding lease liability on the condensed consolidated balance sheet. The lease is due to expire in May 2041. The Company expects to incur leasehold improvement costs during 2021 in order to prepare the building for occupancy. The Company plans to move its Connaught House office employees to the St. Stephen’s Green office in the fourth quarter of 2021. In July 2021, the Company entered into an agreement to assign the Connaught House lease to a third party and the lease assignment will become effective in the fourth quarter of 2021. (2) On March 15, 2021, the Company completed its acquisition of Viela. As part of the acquisition, the Company assumed two leases in Rockville, Maryland for both office and laboratory space and a lease in Gaithersburg, Maryland for office space. On March 18, 2021, the Company entered into a third lease in Rockville, Maryland for office and laboratory space, with a lease commencement date of April 1, 2021.
Schedule of Operating Lease Liabilities Recorded on the Balance Sheet	The table below reconciles the undiscounted cash flows for each of the first five years and total of the remaining years to the lease liabilities recorded on the Company’s condensed consolidated balance sheet as of June 30, 2021 (in thousands): 2021 (July to December) $ 3,937 2022 7,356 2023 11,030 2024 11,855 2025 11,840 Thereafter 102,726 Total lease payments 148,744 Imputed interest (40,696 ) Total lease liabilities $ 108,048

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Remaining Aggregate Potential Milestone Payments Payable Based on Achievement of Net Sales Thresholds	The aggregate potential milestone payments of $225.0 million were payable based on certain TEPEZZA worldwide net sales thresholds being achieved as noted in the following table: TEPEZZA Worldwide Net Sales Threshold Milestone Payment >$250 million $50 million >$375 million $75 million >$500 million $100 million

Share-Based and Long-Term Inc_2

Share-Based and Long-Term Incentive Plans (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity during the six months ended June 30, 2021: Options Weighted Average Exercise Price Weighted Average Contractual Term Remaining (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2020 7,129,615 $ 21.24 4.60 $ 370,073 Assumed in acquisition (1) 1,318,053 41.23 — — Exercised (993,945 ) 28.11 — — Forfeited (58,301 ) 45.06 — — Expired (234 ) 17.31 — — Outstanding as of June 30, 2021 7,395,188 23.69 4.47 517,258 Exercisable as of June 30, 2021 6,602,752 $ 21.67 4.04 $ 475,154 Stock options typically have a contractual term of ten years from grant date. (1) On March 15, 2021, the Company completed its acquisition of Viela. Under the terms of the merger agreement for Viela, all outstanding Viela stock options assumed by the Company with vesting dates after June 1, 2021, were converted into stock options to purchase the Company’s ordinary shares. As of March 15, 2021, options previously exercisable for an aggregate of 2,180,159 shares of Viela’s common stock that were converted at a rate of 0.60 to 1 based on the merger agreement, into options to purchase 1,318,053 of the Company’s ordinary shares, were outstanding.
Summary of Restricted Stock Unit Activity	The following table summarizes restricted stock unit activity for the six months ended June 30, 2021: Number of Units Weighted Average Grant-Date Fair Value Per Unit Outstanding as of December 31, 2020 5,909,120 $ 27.87 Granted 1,991,241 75.12 Vested (2,758,014 ) 23.36 Forfeited (235,032 ) 59.93 Outstanding as of June 30, 2021 4,907,315 $ 48.10
Summary of Performance Stock Unit Awards (PSUs) Activity	The following table summarizes performance stock unit awards (“PSUs”) activity for the six months ended June 30, 2021: Number of Units Weighted Average Grant-Date Fair Value Per Unit Average Illiquidity Discount Recorded Weighted Average Fair Value Per Unit Outstanding as of December 31, 2020 2,610,924 Granted 450,577 $ 93.73 8.64 % $ 85.64 Forfeited (24,450 ) 93.73 9.21 % 85.10 Vested (2,021,657 ) 21.21 2.66 % 20.65 Performance Based Adjustment (1) 512,819 25.42 7.27 % 23.57 Outstanding as of June 30, 2021 1,528,213 (1) Represents adjustment based on the net sales performance criteria meeting 162.5% of target as of December 31, 2020 for the 2020 PSUs (as defined below), the net sales performance criteria meeting 200.0% of target as of December 31, 2020 for the TEPEZZA PSUs (as defined below) and meeting total shareholder return (“TSR”) performance at 200.0% for the PSUs that were awarded to key executive participants on January 5, 2018.
Summary of Significant Valuation Assumptions Related to 2020 PSUs	All PSUs outstanding at June 30, 2021 may vest in a range of between 0% and 200%, with the exception of the modified KRYSTEXXA 2020 Net Sales PSUs which are capped at 150%, based on the performance metrics described above. The Company accounts for the 2020 PSUs and 2021 PSUs as equity-settled awards in accordance with ASC 718, Compensation-Stock Compensation Valuation date stock price $ 72.54 Expected volatility 45.8 % Risk free rate 0.2 %
Summary of Share-Based Compensation Expense	The following table summarizes share-based compensation expense included in the Company’s condensed consolidated statements of operations for the six months ended June 30, 2021 and 2020 (in thousands): For the Six Months Ended June 30, 2021 2020 Share-based compensation expense Cost of goods sold $ 5,080 $ 3,977 Research and development 17,776 8,928 Selling, general and administrative 92,734 70,573 Total share-based compensation expense $ 115,590 $ 83,478

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
(Benefit) Expense for Income Taxes	The following table presents the (benefit) expense for income taxes for the three and six months ended June 30, 2021 and 2020 (in thousands): For June 30, For June 30, 2021 2020 2021 2020 Income (loss) before (benefit) expense for income taxes $ 115,633 $ 2,954 $ (55,469 ) $ (29,663 ) (Benefit) expense for income taxes (42,484 ) 82,964 (90,235 ) 63,938 Net income (loss) $ 158,117 $ (80,010 ) $ 34,766 $ (93,601 )

Basis of Presentation and Bus_2

Basis of Presentation and Business Overview - Additional Information (Detail) $ / shares in Units, $ in Thousands	Mar. 15, 2021USD ($)$ / shares	Jun. 30, 2021USD ($)Segment$ / shares
Basis Of Presentation [Line Items]
Number of reportable segments | Segment		2
Viela Bio [Member]
Basis Of Presentation [Line Items]
Business Acquisition, Date of Acquisition Agreement	Mar. 15, 2021
Share Price | $ / shares		$ 53
Total consideration for acquisition | $	$ 3,000,000	$ 2,994,091
Cash acquired from acquisition | $	$ 342,300	$ 342,300
Viela Bio [Member] | Ordinary Shares [Member]
Basis Of Presentation [Line Items]
Share Price | $ / shares	$ 53

Net Income (Loss) per Share - B

Net Income (Loss) per Share - Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic net income (loss) per share calculation:
Numerator - net income (loss)	$ 158,117	$ (123,351)	$ (80,010)	$ (13,591)	$ 34,766	$ (93,601)
Denominator - weighted average ordinary shares outstanding	225,119,684		192,705,535		224,523,538	191,426,864
Basic net income (loss) per share	$ 0.70		$ (0.42)		$ 0.15	$ (0.49)
Diluted net income (loss) per share calculation:
Numerator - net income (loss)	$ 158,117	$ (123,351)	$ (80,010)	$ (13,591)	$ 34,766	$ (93,601)
Denominator - weighted average ordinary shares outstanding	235,191,860		192,705,535		234,719,830	191,426,864
Diluted net income (loss) per share	$ 0.67		$ (0.42)		$ 0.15	$ (0.49)

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Exchangeable Senior Notes [Member]
Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share		12.4		13.1
Interest rate		2.50%		2.50%
Equity Awards [Member]
Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share	0.9	9.7	2.9	12

Acquisitions, Divestitures an_3

Acquisitions, Divestitures and Other Arrangements - Additional Information (Detail)	Mar. 15, 2021USD ($)$ / shares	Apr. 01, 2020USD ($)	Jan. 02, 2020USD ($)	May 08, 2017USD ($)	Jul. 31, 2021USD ($)	Feb. 28, 2021USD ($)	Jul. 31, 2020USD ($)	Apr. 30, 2020USD ($)	Jul. 31, 2019USD ($)	Jun. 30, 2021USD ($)$ / shares$ / SFr	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)$ / SFr	Mar. 31, 2020CHF (SFr)	Jun. 30, 2021USD ($)$ / shares$ / SFr	Jun. 30, 2021CHF (SFr)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)$ / SFr	Dec. 31, 2020CHF (SFr)	Jun. 30, 2021CHF (SFr)$ / SFr	Mar. 31, 2021USD ($)	Jul. 16, 2019USD ($)	Jan. 03, 2019USD ($)
Business Acquisition [Line Items]
Outstanding principal amount										$ 2,614,026,000				$ 2,614,026,000			$ 1,018,026,000				$ 625,000,000
Acquisition-related costs										30,626,000	$ 46,988,000			80,017,000		$ 47,272,000
Net reduction in goodwill										7,400,000				(7,357,000)
Net loss										2,000,000				2,000,000
Milestone and royalty payments								$ 55,000,000
Developed technology and other intangible assets, net										$ 3,119,709,000				3,119,709,000			1,782,962,000
Roche [Member]
Business Acquisition [Line Items]
Milestone Payment | SFr																			SFr 103,000,000
Milestone incurred												$ 5,200,000	SFr 5,000,000	$ 46,500,000	SFr 43,000,000
Currency exchange rate | $ / SFr										1.0813		1.0382		1.0813					1.0813
S R One And Lundbeckfond
Business Acquisition [Line Items]
Developed technology and other intangible assets, net											$ 110,000,000					110,000,000
UPLIZNA [Member]
Business Acquisition [Line Items]
Inventory, raw materials										$ 2,300				$ 2,300						$ 10,100
Inventory, work in Process, gross										1,900				1,900						119,000
Inventories, net										151,600				151,600						149,300
Inventory, finished goods, gross										400				400						20,200
Inventory step-up expense										$ 8,000				8,000						$ 7,100
TEPEZZA [Member]
Business Acquisition [Line Items]
Developed technology and other intangible assets, net																	120,800,000
TEPEZZA [Member] | Roche [Member]
Business Acquisition [Line Items]
Milestone incurred																	$ 53,800,000	SFr 50,000,000
T E P E Z Z A Developed Technology
Business Acquisition [Line Items]
Milestone incurred														$ 46,500,000	SFr 43,000,000
Currency exchange rate | $ / SFr																	1.0813
Viela Bio [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement	Mar. 15, 2021
Share Price | $ / shares										$ 53				$ 53
Outstanding principal amount	$ 1,600,000,000
Total consideration for acquisition	3,000,000,000													$ 2,994,091,000
Cash acquired from acquisition	$ 342,300,000													342,300,000
Acquisition-related costs														$ 28,600,000
Net reduction in goodwill										$ 7,400,000
Acquisition-date fair value at a discount rate														11.50%	11.50%
Finite-lived intangible assets, remaining amortization period														14 years	14 years
Acquisition-date fair value at a discount rate														23.80%	23.80%
Deferred tax liability										451,100				$ 451,100
Net income (loss), Pro forma														3,962,000		$ (259,891,000)
Upfront cash payments														$ 2,914,407,000
Viela Bio [Member] | Acquisition Related Costs [Member]
Business Acquisition [Line Items]
Net income (loss), Pro forma			$ (86,600,000)
Viela Bio [Member] | Research and Development Expense
Business Acquisition [Line Items]
Acquisition-date fair value at a discount rate														12.50%	12.50%
Curzion Pharmaceuticals Inc [Member]
Business Acquisition [Line Items]
Upfront cash payment										45,000,000				$ 45,000,000
Upfront cash payments		$ 45,000,000
RAVICTI And BUPHENYL [Member]
Business Acquisition [Line Items]
Milestone Payment																	$ 5,400,000
Net loss																	4,900,000
River Vision [Member]
Business Acquisition [Line Items]
Cash acquired from acquisition				$ 6,300,000
Milestone Payment										325,000,000				$ 325,000,000
Percentage of equity interests acquired				100.00%
Business acquisition agreement date				May 8, 2017
Upfront cash payments				$ 150,300,000
Percentage of net sales in earn-out payment														3.00%	3.00%
Net sales minimum limit for royal payment														$ 300,000,000
River Vision [Member] | U.S. Food and Drug Administration (FDA) Approval [Member]
Business Acquisition [Line Items]
Milestone Payment										100,000,000		$ 100,000,000		100,000,000
River Vision [Member] | Teprotumumab [Member] | Net Sales Thresholds [Member]
Business Acquisition [Line Items]
Milestone Payment										225,000,000				225,000,000
River Vision [Member] | TEPEZZA [Member]
Business Acquisition [Line Items]
Milestone incurred																	67,000,000
Arrowhead Pharmaceuticals [Member]
Business Acquisition [Line Items]
Upfront cash payments					$ 40,000,000
Potential additional contingent consideration payment									$ 660,000,000
Upfront cash payment										40,000				$ 40,000
HemoShear [Member]
Business Acquisition [Line Items]
Upfront cash payments																	$ 30,000,000
Potential additional contingent consideration payment									160,000,000
Upfront cash payment										$ 30,000
HemoShear [Member]
Business Acquisition [Line Items]
Upfront cash payment																						$ 2,000,000
Business combination progress payments paid under collaboration agreement.						$ 3,000,000	$ 3,000,000		$ 4,000,000
Ordinary Shares [Member] | Viela Bio [Member]
Business Acquisition [Line Items]
Share Price | $ / shares	$ 53

Acquisitions, Divestitures an_4

Acquisitions, Divestitures and Other Arrangements - Schedule of Total Consideration for the Acquisitions (Detail) - Viela Bio [Member] - USD ($) $ in Thousands	Mar. 15, 2021	Jun. 30, 2021
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Equity value (54,988,820 shares at $53.00 per share)		$ 2,914,407
Net settlements on the exercise of stock options		78,554
Consideration for exchange of Viela stock options		1,130
Total consideration	$ 3,000,000	$ 2,994,091

Acquisitions, Divestitures an_5

Acquisitions, Divestitures and Other Arrangements - Schedule of Total Consideration for the Acquisitions ((Parenthetical) (Detail) - Viela Bio [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Equity value, shares | shares	54,988,820
Share Price | $ / shares	$ 53

Acquisitions, Divestitures an_6

Acquisitions, Divestitures and Other Arrangements - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Detail) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Goodwill	$ 1,069,031,000	$ 413,669,000
Viela Bio [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Deferred tax liabilities, net	(451,100)
Viela Bio [Member] | Before [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Deferred tax liabilities, net	(457,928,000)
Accrued expenses and other current liabilities	(73,401,000)
Other long-term liabilities	(22,631,000)
Accounts payable	(4,768,000)
Accrued trade discounts and rebates	(1,492,000)
Marketable securities	400,000
Property, plant and equipment	1,747,000
Other assets	3,253,000
Accounts receivable	8,053,000
Prepaid expenses and other current assets	16,444,000
Inventories	149,348,000
Cash and cash equivalents	342,347,000
In-process research and development	910,000,000
Developed technology	1,460,000,000
(Liabilities assumed) and assets acquired	2,331,372,000
Goodwill	662,719,000
Fair value of consideration paid	2,994,091,000
Viela Bio [Member] | Adjustments [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Deferred tax liabilities, net	6,869,000
Accrued expenses and other current liabilities	(335,000)
Accrued trade discounts and rebates	(373,000)
Accounts receivable	(267,000)
Prepaid expenses and other current assets	(837,000)
Inventories	2,300,000
(Liabilities assumed) and assets acquired	7,357,000
Goodwill	(7,357,000)
Viela Bio [Member] | After [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Deferred tax liabilities, net	(451,059,000)
Accrued expenses and other current liabilities	(73,736,000)
Other long-term liabilities	(22,631,000)
Accounts payable	(4,768,000)
Accrued trade discounts and rebates	(1,865,000)
Marketable securities	400,000
Property, plant and equipment	1,747,000
Other assets	3,253,000
Accounts receivable	7,786,000
Prepaid expenses and other current assets	15,607,000
Inventories	151,648,000
Cash and cash equivalents	342,347,000
In-process research and development	910,000,000
Developed technology	1,460,000,000
(Liabilities assumed) and assets acquired	2,338,729,000
Goodwill	655,362,000
Fair value of consideration paid	$ 2,994,091,000

Acquisitions, Divestitures an_7

Acquisitions, Divestitures and Other Arrangements - Gain (Loss) on Sale of Assets (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales	$ 832,548		$ 462,779		$ 1,174,954	$ 818,688
Net income (loss)	$ 158,117	$ (123,351)	$ (80,010)	$ (13,591)	34,766	(93,601)
Viela Bio [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales					1,174,954	818,688
Net income (loss)					34,766	(93,601)
Net sales, Pro forma Adjustments					10,588
Net income (loss), Pro forma Adjustemnts					(30,804)	(166,290)
Net sales, Pro forma					1,185,542	818,688
Net income (loss), Pro forma					$ 3,962	$ (259,891)

Inventories - Components of Inv

Inventories - Components of Inventories (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 53,112	$ 11,760
Work-in-process	90,840	33,167
Finished goods	114,724	30,356
Inventories, net	$ 258,676	$ 75,283

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Inventory [Line Items]
Raw materials	$ 53,112	$ 53,112	$ 11,760
Work-in-process	90,840	90,840	33,167
Finished goods	114,724	114,724	$ 30,356
UPLIZNA [Member]
Inventory [Line Items]
Raw materials	10,100	10,100
Work-in-process	120,900	120,900
Finished goods	20,600	20,600
Inventory set-up expense	$ 7,100	$ 8,000

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Advance payments for inventory	$ 134,716	$ 137,680
Deferred charge for taxes on intercompany profit	85,070	52,306
Prepaid income taxes and income tax receivable	63,609	102
Rabbi trust assets	23,885	18,423
Other prepaid expenses and other current assets	57,833	43,434
Prepaid expenses and other current assets	$ 365,113	$ 251,945

Property and Equipment - Proper

Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 253,886	$ 236,828
Less accumulated depreciation	(33,744)	(47,791)
Property and equipment, net	220,142	189,037
Building [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	128,266	80,341
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	38,880	38,076
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28,377	63,656
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,669	4,695
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	14,488	14,618
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	12,293	5,973
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,847	26,323
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,066	$ 3,146

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 26, 2020USD ($)Building	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Feb. 26, 2020a	Feb. 26, 2020ft²
Property, Plant and Equipment [Line Items]
Depreciation expense		$ 3,393	$ 6,907	$ 7,844	$ 14,072
Deerfield, Illinois [Member]
Property, Plant and Equipment [Line Items]
Purchase of building for consideration and transaction costs	$ 118,500
Number of building purchased | Building	3
Office space						70	650,000

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	Mar. 15, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross		$ 1,069,000,000			$ 1,069,000,000		$ 413,700,000
Goodwill recognized on acquisition					662,719,000
Net reduction in goodwill		7,400,000			(7,357,000)
Accumulated goodwill impairment losses		0			0
Amortization expense of developed technology		88,523,000		$ 66,749,000	154,892,000	$ 125,324,000
UPLIZNA [Member] | Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized payments of intangible assets	$ 1,460,000,000
TEPEZZA [Member] | Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized payments of intangible assets							$ 336,000,000
Viela Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill recognized on acquisition		$ 655,300,000	$ 662,700,000
Capitalized payments of intangible assets					$ 880,000,000

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Goodwill for Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Goodwill [Line Items]
Goodwill beginning balance		$ 413,669
Goodwill recognized on acquisition		662,719
Net reduction in goodwill	$ 7,400	(7,357)
Goodwill ending balance	1,069,031	1,069,031
Orphan [Member]
Goodwill [Line Items]
Goodwill beginning balance		357,498
Goodwill recognized on acquisition		662,719
Net reduction in goodwill		(7,357)
Goodwill ending balance	1,012,860	1,012,860
Inflammation [Member]
Goodwill [Line Items]
Goodwill beginning balance		56,171
Goodwill ending balance	$ 56,171	$ 56,171

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Cost Basis		$ 5,473,624	$ 3,101,986
Accumulated Amortization		(1,473,915)	(1,319,024)
Net Book Value		3,999,709	1,782,962
Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Cost Basis		4,585,524	3,093,886
Accumulated Amortization		(1,468,423)	(1,313,934)
Net Book Value		3,117,101	1,779,952
In Process Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Cost Basis	[1]	880,000
Net Book Value	[1]	880,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost Basis		8,100	8,100
Accumulated Amortization		(5,492)	(5,090)
Net Book Value		$ 2,608	$ 3,010
[1]	The Company acquired IPR&D of $910.0 million relating to Viela. On March 24, 2021, the Company announced that its strategic partner, Mitsubishi Tanabe Pharma Corporation, had received manufacturing and marketing approval of UPLIZNA in Japan. As a result, the Company transferred $30.0 million of IPR&D to developed technology. As of June 30, 2021, the remaining IPR&D relating to the Viela acquisition was $880.0 million.

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Amortizable Intangible Assets - (Parenthetical) (Detail) - Viela Acquisition [Member] $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Finite-Lived Intangible Assets [Line Items]
Capitalized payments of intangible assets	$ 880
In Process Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized payments of intangible assets	910
Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Total consideration for acquisition	$ 30

Goodwill and Intangible Asset_6

Goodwill and Intangible Assets - Estimated Future Amortization Expense (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
2021 (July to December)	$ 179,397
2022	354,891
2023	354,376
2024	352,951
2025	350,700
Thereafter	1,527,394
Total	$ 3,119,709	$ 1,782,962

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilites - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Payroll-related expenses	$ 108,720	$ 121,577
Accrued royalties	68,104	68,006
Accrued upfront and milestone payments	46,500	123,442
Allowances for returns	37,881	40,918
R&D and manufacturing programs	36,992	17,289
Advertising and marketing	28,505	12,428
Consulting and professional services	25,310	21,893
Deferred revenues	20,835
Pricing review liability	20,068	16,046
Accrued interest	15,688	14,207
Accrued other	69,896	49,761
Accrued expenses and other current liabilities	$ 478,499	$ 485,567

Accrued Trade Discounts and R_3

Accrued Trade Discounts and Rebates - Schedule of Accrued Trade Discounts and Rebates (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Commercial Rebates and Wholesaler Fees [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	$ 53,902	$ 82,646
Accrued Co-Pay and Other Patient Assistance [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	60,799	96,924
Accrued Government Rebates and Chargebacks [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	191,663	172,893
Accrued Trade Discounts and Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	306,364	352,463
Invoiced Commercial Rebates and Wholesaler Fees, Co pay and Other Patient Assistance Costs, and Government Rebates and Chargebacks in Accounts Payable [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	10,324	1,452
Customer-related Accruals and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Total customer-related accruals and allowances	$ 316,688	$ 353,915

Accrued Trade Discounts and R_4

Accrued Trade Discounts and Rebates - Schedule of Customer-Related Accruals and Allowances (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Government Rebates and Chargebacks [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 172,893
Current provisions relating to sales	342,609
Adjustments relating to prior-year sales	(9,376)
Payments relating to sales	(171,269)
Payments relating to prior-year sales	(144,605)
Ending Balance	191,663
Government Rebates and Chargebacks [Member] | Viela [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Viela acquisition	1,411
Wholesaler Fees and Commercial Rebates [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	84,098
Current provisions relating to sales	145,684
Adjustments relating to prior-year sales	(2,361)
Payments relating to sales	(83,411)
Payments relating to prior-year sales	(79,854)
Ending Balance	64,226
Wholesaler Fees and Commercial Rebates [Member] | Viela [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Viela acquisition	70
Co-Pay and Other Patient Assistance [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	96,924
Current provisions relating to sales	404,720
Adjustments relating to prior-year sales	(4,516)
Payments relating to sales	(344,328)
Payments relating to prior-year sales	(92,012)
Ending Balance	60,799
Co-Pay and Other Patient Assistance [Member] | Viela [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Viela acquisition	11
Customer-related Accruals and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	353,915
Current provisions relating to sales	893,013
Adjustments relating to prior-year sales	(16,253)
Payments relating to sales	(599,008)
Payments relating to prior-year sales	(316,471)
Ending Balance	316,688
Customer-related Accruals and Allowances [Member] | Viela [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Viela acquisition	$ 1,492

Segment and Other Information -

Segment and Other Information - Additional Information (Detail) - Segment	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Number of reportable segments			2
Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Consolidated receivable/sales percentage to major customers	100.00%	100.00%	100.00%	100.00%
Customer Concentration Risk [Member] | Sales Revenue [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Consolidated receivable/sales percentage to major customers			10.00%

Segment and Other Information_2

Segment and Other Information - Summary of Net Sales by Medicine for Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total net sales	$ 832,548	$ 462,779	$ 1,174,954	$ 818,688
TEPEZZA [Member]
Segment Reporting Information [Line Items]
Total net sales	453,255	165,936	455,320	189,387
KRYSTEXXA [Member]
Segment Reporting Information [Line Items]
Total net sales	130,317	75,201	237,074	168,450
RAVICTI [Member]
Segment Reporting Information [Line Items]
Total net sales	68,426	65,550	141,243	126,738
PROCYSBI [Member]
Segment Reporting Information [Line Items]
Total net sales	49,775	41,357	93,138	79,700
ACTIMMUNE [Member]
Segment Reporting Information [Line Items]
Total net sales	27,777	28,299	56,540	54,840
UPLIZNA [Member]
Segment Reporting Information [Line Items]
Total net sales	14,475		16,348
BUPHENYL [Member]
Segment Reporting Information [Line Items]
Total net sales	2,262	2,846	3,922	5,160
QUINSAIR [Member]
Segment Reporting Information [Line Items]
Total net sales	222	59	431	336
Orphan Segment Net Sales [Member]
Segment Reporting Information [Line Items]
Total net sales	746,509	379,248	1,004,016	624,611
PENNSAID 2% [Member]
Segment Reporting Information [Line Items]
Total net sales	48,941	35,048	94,758	76,611
DUEXIS [Member]
Segment Reporting Information [Line Items]
Total net sales	22,110	27,798	41,575	59,145
RAYOS [Member]
Segment Reporting Information [Line Items]
Total net sales	13,406	14,459	28,678	32,668
VIMOVO [Member]
Segment Reporting Information [Line Items]
Total net sales	1,582	6,226	5,927	25,653
Inflammation [Member]
Segment Reporting Information [Line Items]
Total net sales	$ 86,039	$ 83,531	$ 170,938	$ 194,077

Segment and Other Information_3

Segment and Other Information - Summary of Reconciliations of Segment Operating Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment operating income:
Operating income	$ 138,515	$ 37,864	$ (21,503)	$ 21,373
Amortization and step-up:
Intangible amortization expense	(88,523)	(66,749)	(154,892)	(125,324)
Inventory step-up expense	(7,091)		(8,002)
Share-based compensation	(54,424)	(27,057)	(115,590)	(83,478)
Upfront, progress and milestone payments related to license and collaboration agreements	(46,500)	(3,000)	(49,500)	(3,000)
Acquisition/divestiture-related costs	(30,626)	(46,988)	(80,017)	(47,272)
Interest expense, net	(22,581)	(18,571)	(36,041)	(35,915)
Depreciation	(3,393)	(6,907)	(7,844)	(14,072)
Restructuring and realignment costs	(930)		(7,023)
Other (expense) income, net	(262)	632	2,962	1,074
Fees related to refinancing activities				(54)
Foreign exchange (loss) gain	(39)	283	(887)	1,059
Loss on debt extinguishment		(17,254)		(17,254)
Impairment of long-lived assets		(1,072)	(12,371)	(1,072)
Drug substance harmonization costs				(290)
Gain on sale of asset	2,000		2,000
Income (loss) before (benefit) expense for income taxes	115,633	2,954	(55,469)	(29,663)
Orphan [Member]
Segment operating income:
Operating income	321,235	151,541	322,289	205,897
Inflammation [Member]
Segment operating income:
Operating income	$ 46,767	$ 38,096	$ 89,447	$ 90,038

Segment and Other Information_4

Segment and Other Information - Schedule of Gross Sales to Customers Included in Reportable Segments and All Other Customers as a Group (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 1,323,194	$ 897,993	$ 2,084,726	$ 1,701,516
Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	100.00%	100.00%	100.00%	100.00%
Customer A [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 410,436	$ 314,288	$ 659,176	$ 561,063
Customer A [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	31.00%	35.00%	32.00%	33.00%
Customer B [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 342,148	$ 194,576	$ 526,835	$ 401,853
Customer B [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	26.00%	22.00%	25.00%	24.00%
Customer C [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 240,290	$ 160,814	$ 358,327	$ 294,689
Customer C [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	18.00%	18.00%	17.00%	17.00%
Customer D [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 212,820	$ 112,676	$ 303,439	$ 197,464
Customer D [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	16.00%	13.00%	15.00%	12.00%
Other Customers [Member]
Segment Reporting Information [Line Items]
Gross Sales, Amount	$ 117,500	$ 115,639	$ 236,949	$ 246,447
Other Customers [Member] | Customer Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Gross Sales, Percentage	9.00%	12.00%	11.00%	14.00%

Segment and Other Information_5

Segment and Other Information - Summary of Net Sales Attributed to Geographic Sources (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total net sales	$ 832,548	$ 462,779	$ 1,174,954	$ 818,688
United States [Member]
Segment Reporting Information [Line Items]
Total net sales	$ 830,185	$ 460,827	$ 1,170,515	$ 814,843
United States [Member] | Geographic Concentration Risk [Member] | Sales Revenue [Member]
Segment Reporting Information [Line Items]
Total Net Sales, Percentage	100.00%	100.00%	100.00%	100.00%
Rest of World [Member]
Segment Reporting Information [Line Items]
Total net sales	$ 2,363	$ 1,952	$ 4,439	$ 3,845

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	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	$ 666,885	$ 1,924,423
Total liabilities at fair value	(23,885)	(18,423)
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	643,000	1,906,000
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	23,885	18,423
Other Long-term Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities at fair value	(23,885)	(18,423)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	666,885	1,924,423
Total liabilities at fair value	(23,885)	(18,423)
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	643,000	1,906,000
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	23,885	18,423
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	$ (23,885)	$ (18,423)

Debt Agreements - Outstanding D

Debt Agreements - Outstanding Debt Balances (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jul. 16, 2019
Debt Instrument [Line Items]
Total face value	$ 2,614,026	$ 1,018,026	$ 625,000
Debt discount	(13,177)	(10,061)
Deferred financing fees	(24,405)	(4,586)
Total long-term debt	2,576,444	1,003,379
Less: current maturities	16,000
Long-term debt, net of current maturities	2,560,444	1,003,379
Term Loan Facility due 2028 [Member]
Debt Instrument [Line Items]
Total face value	1,596,000
Term Loan Facility due 2026 [Member]
Debt Instrument [Line Items]
Total face value	418,026	418,026
Senior Notes due 2027 [Member]
Debt Instrument [Line Items]
Total face value	$ 600,000	$ 600,000

Debt Agreements - Term Loan Fac

Debt Agreements - Term Loan Facility and Revolving Credit Facility - Additional Information (Detail) - USD ($)	Sep. 15, 2021	Mar. 15, 2021	Dec. 18, 2019	Mar. 11, 2019	Jun. 30, 2021	Dec. 31, 2020	Jul. 16, 2019
Debt Instrument [Line Items]
Outstanding principal amount					$ 2,614,026,000	$ 1,018,026,000	$ 625,000,000
Refinancing Loans
Debt Instrument [Line Items]
Line of credit facility borrowing capacity			$ 418,000,000
LIBOR floor rate			0.50%
Debt instrument variable rate			2.00%
Interest rate description			The Incremental Loans were incurred as a separate class of term loans under the Credit Agreement with substantially the same terms of the December 2019 Refinancing Loans.  The Borrower used the proceeds of the Incremental Loans to fund a portion of the consideration payable in the acquisition of Viela.  The Incremental Loans bear interest at a rate, at Borrower’s option, equal to the London Inter-Bank Offered Rate (“LIBOR”), plus 2.00% per annum (subject to a 0.50% LIBOR floor) or the adjusted base rate plus 1.00% per annum, with a step-down to LIBOR plus 1.75% per annum or the adjusted base rate plus 0.75% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00.  The adjusted base rate is defined as the greatest of (a) LIBOR (using one-month interest period) plus 1.00%, (b) the prime rate, (c) the federal funds rate plus 0.50%, and (d) 1.00%.
Debt instrument, variable interest rate					2.38%
Debt instrument, effective interest rate					2.67%
Refinancing Loans | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			1.75%
Refinancing Loans | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument leverage ratio			2.00%
Refinancing Loans | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument leverage ratio			1.00%
Refinancing Loans | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument variable rate			1.00%
Refinancing Loans | London Interbank Offered Rate (LIBOR) | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			0.75%
2019 Term Loan Facility [Member]
Debt Instrument [Line Items]
LIBOR floor rate			0.00%
Debt instrument variable rate			2.25%
Interest rate description					The December 2019 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 May 22, 2019 (the “Refinanced Loans”) to effectuate a repricing of the Refinanced Loans.  The Borrower used the proceeds of the December 2019 Refinancing Loans to repay the Refinanced Loans, which totaled approximately $418.0 million.  The December 2019 Refinancing Loans bear interest at a rate, at the Borrower’s option, equal to LIBOR plus 2.25% per annum (subject to a 0.00% LIBOR floor) or the adjusted base rate plus 1.25% per annum, with a step-down to LIBOR plus 2.00% per annum or the adjusted base rate plus 1.00% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00.
Percent Of Premium On Repayment Of Debt			1.00%
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%
Credit agreement, description					The Borrower is 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 Incremental Loans, a 1% premium will apply to a repayment of the Incremental 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 September 15, 2021.  The Borrower is 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 Incremental Loans will amortize in equal quarterly installments in an aggregate annual amount equal to 1% of the original principal amount thereof, with any remaining balance payable on March 15, 2028, the final maturity date of the Incremental Loans.  The principal amount of the December 2019 Refinancing Loans is due and payable on May 22, 2026, the final maturity date of the December 2019 Refinancing Loans.
Maturity date of debt instrument			May 22, 2026
2019 Term Loan Facility [Member] | Horizon Pharma Subsidiaries [Member]
Debt Instrument [Line Items]
Cut off percentage for defining limited liability subsidiaries, portion of capital stock held maximum			65.00%
2019 Term Loan Facility [Member] | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			2.00%
2019 Term Loan Facility [Member] | Scenario Forecast
Debt Instrument [Line Items]
Percent Of Premium On Repayment Of Debt	1.00%
Percentage of debt instrument amortization of principal amount	1.00%
2019 Term Loan Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument leverage ratio			2.00%
Leverage ratio less than applicable margin			1.00%
First lien leverage ratio			175.00%
2019 Term Loan Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument leverage ratio			1.00%
Leverage ratio less than applicable margin			2.00%
First lien leverage ratio			225.00%
2019 Term Loan Facility [Member] | Base Rate
Debt Instrument [Line Items]
Debt instrument variable rate			1.25%
2019 Term Loan Facility [Member] | Base Rate | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			1.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
LIBOR floor rate			0.00%
Interest rate description			The loans under the Revolving Credit Facility bear interest, at the Borrower’s option, at a rate equal to either LIBOR plus an applicable margin of 2.25% per annum (subject to a LIBOR floor of 0.00%), or the adjusted base rate plus 1.25% per annum, with a step-down to LIBOR plus 2.00% per annum or the adjusted base rate plus 1.00% per annum at the time the Company’s leverage ratio is less than or equal to 2.00 to 1.00.
Minimum percentage of total commitments					25.00%
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument variable rate			2.25%
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			2.00%
Revolving Credit Facility [Member] | Base Rate
Debt Instrument [Line Items]
Debt instrument variable rate			1.25%
Revolving Credit Facility [Member] | Base Rate | Scenario, Plan
Debt Instrument [Line Items]
Debt instrument variable rate			1.00%
Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate					2.50%
Debt instrument, effective interest rate					2.75%
Horizon Pharma USA Inc [Member] | New Incremental Revolving Commitments [Member]
Debt Instrument [Line Items]
Outstanding principal amount		$ 1,600,000,000
Aggregate principal amount				$ 200,000,000
Line of credit facility additional borrowing capacity				$ 275,000,000
Line of credit facility termination period				2024-03
Horizon Pharma USA Inc [Member] | May 2019 Refinancing Loans [Member]
Debt Instrument [Line Items]
Line of credit facility borrowing capacity		$ 418,000,000
Horizon Pharma USA Inc [Member] | Letter of Credit Sub-facility [Member]
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity				$ 50,000,000
Hyperion Therapeutics, Inc. [Member] | Refinancing Loans | Underwritten Public Offering
Debt Instrument [Line Items]
Debt instrument, fair value					$ 414,900,000
Hyperion Therapeutics, Inc. [Member] | Term Loan Facility [Member] | Underwritten Public Offering
Debt Instrument [Line Items]
Debt instrument, fair value					$ 1,586,000,000

Debt Agreements - 2027 Senior N

Debt Agreements - 2027 Senior Notes - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 16, 2019	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Senior notes			$ 2,560,444	$ 1,003,379
Outstanding principal amount	$ 625,000		$ 2,614,026	$ 1,018,026
Senior Secured Term Loan [Member]
Debt Instrument [Line Items]
Outstanding principal amount	$ 100,000
2027 Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	5.50%		5.50%
Cash on hand	$ 65,000
Debt instrument, frequency of periodic payment		semiannually
Debt instrument redemption description		the 2027 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 August 1, 2022, some or all of the 2027 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 August 1, 2022, up to 40% of the aggregate principal amount of the 2027 Senior Notes may be redeemed at a redemption price of 105.5% of the aggregate principal amount thereof, plus accrued and unpaid interest, with the net proceeds of certain equity offerings.  In addition, the 2027 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 2027 Senior Notes, HTUSA or any guarantor is or would be required to pay additional amounts as a result of certain tax related events.
Debt instrument, effective interest rate			5.76%
Debt instrument, fair value			$ 636,000
2027 Senior Notes [Member] | Prior to August 1, 2022 [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount	105.50%
2027 Senior Notes [Member] | Prior to August 1, 2022 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Redemption amount as percentage of aggregate principal amount	40.00%
2027 Senior Notes [Member] | Prior to August 1, 2022, Some or All of Aggregate Principal Amount [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount	100.00%
2027 Senior Notes [Member] | After August 1, 2022, in Whole But Not in Part [Member]
Debt Instrument [Line Items]
Redemption price as percentage of aggregate principal amount	100.00%
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	6.625%
Outstanding principal amount	$ 225,000
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	8.75%
Outstanding principal amount	$ 300,000
Horizon Pharma USA Inc [Member] | 2027 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes	$ 600,000
Interest rate	5.50%
Maturity date of debt instrument	Aug. 1, 2027
Debt instrument redemption description		If the Company undergoes a change of control, HTUSA will be required to make an offer to purchase all of the 2027 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, subject to certain exceptions.  If the Company or certain of its subsidiaries engages in certain asset sales, HTUSA will be required under certain circumstances to make an offer to purchase the 2027 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%

Lease Obligations - Schedule of

Lease Obligations - Schedule of Office Space Lease Agreements in Place for Real Properties (Detail)	6 Months Ended
	Jun. 30, 2021ft²
Dublin Office (St Stephen’s Green) [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	63,000
Lease Expiry Date	May 4, 2041
Dublin Office (Connaught House) [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	18,900
Lease Expiry Date	Nov. 4, 2029
Lake Forest Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	160,000
Lease Expiry Date	Mar. 31, 2031
Novato Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	61,000
Lease Expiry Date	Aug. 31, 2021
South San Francisco Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	20,000
Lease Expiry Date	Jan. 31, 2030
Rockville Maryland Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	24,500
Rockville Maryland Office [Member] | Minimum [Member]
Lessee Lease Description [Line Items]
Lease Expiry Date	Aug. 31, 2023
Rockville Maryland Office [Member] | Maximum [Member]
Lessee Lease Description [Line Items]
Lease Expiry Date	Apr. 30, 2026
Chicago Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	9,200
Lease Expiry Date	Dec. 31, 2028
Gaithersburg Maryland Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	7,200
Lease Expiry Date	Jun. 30, 2022
Washington, D.C. Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	6,000
Lease Expiry Date	Sep. 15, 2022
Mannheim Office [Member]
Lessee Lease Description [Line Items]
Approximate Square Feet	4,800
Lease Expiry Date	Dec. 31, 2022

Lease Obligations - Schedule _2

Lease Obligations - Schedule of Office Space Lease Agreements in Place for Real Properties (Parenthetical) (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Oct. 31, 2019ft²
Lessee Lease Description [Line Items]
Right-of-use assets	$ 85,100	$ 34,400
Number of leases	2
Dublin Office [Member]
Lessee Lease Description [Line Items]
Approximate square feet of office space | ft²			63,000
Right-of-use assets	$ 60,900
Lease expiration	2041-05

Lease Obligations - Additional

Lease Obligations - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Lessee Lease Description [Line Items]
Right-of-use assets	$ 85.1		$ 85.1		$ 34.4
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets		Other assets		Other assets
Lease liability, current	$ 4.6		$ 4.6		$ 4.1
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent		us-gaap:AccruedLiabilitiesCurrent		us-gaap:AccruedLiabilitiesCurrent
Lease liability, noncurrent	$ 103.5		$ 103.5		$ 43.2
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities		Other long-term liabilities		Other long-term liabilities
Rent expense	$ 2.4	$ 1.8	$ 4	$ 3.4
Weighted-average discount rate	4.88%		4.88%
Weighted-average remaining lease term	15 years 21 days		15 years 21 days
Lake Forest Office [Member]
Lessee Lease Description [Line Items]
Impairment charges			$ 12.4

Lease Obligations - Schedule _3

Lease Obligations - Schedule of Operating Lease Liabilities Recorded on the Balance Sheet (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
Operating Lease liabilities, 2021 (July to December)	$ 3,937
Operating Lease liabilities, 2022	7,356
Operating Lease liabilities, 2023	11,030
Operating Lease liabilities, 2024	11,855
Operating Lease liabilities, 2025	11,840
Operating Lease liabilities, Thereafter	102,726
Operating Lease liabilities,Total lease payments	148,744
Operating Lease liabilities, Imputed interest	(40,696)
Total lease liabilities	$ 108,048

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) € in Millions	Jun. 18, 2021USD ($)	Apr. 01, 2020USD ($)	May 08, 2017USD ($)	Apr. 30, 2020	Mar. 31, 2020USD ($)$ / SFr	Mar. 31, 2020CHF (SFr)$ / SFr	Jun. 30, 2021USD ($)$ / SFr$ / €	Jun. 30, 2021CHF (SFr)	Jun. 30, 2021EUR (€)	Dec. 31, 2020USD ($)	Jun. 30, 2021CHF (SFr)$ / SFr$ / €
Loss Contingencies [Line Items]
Amount committed in investment							$ 48,100,000
Net cash payments for investment							7,600,000
Other Income, Net [Member]
Loss Contingencies [Line Items]
Investment income							1,700,000
Other Assets [Member]
Loss Contingencies [Line Items]
Amount committed in investment							20,200,000
TEPEZZA [Member]
Loss Contingencies [Line Items]
Upfront cash payment										$ 30,000,000
Maximum payment to be made upon attainment of milestones										$ 160,000,000
River Vision [Member]
Loss Contingencies [Line Items]
Milestone Payment							$ 325,000,000
Upfront cash payments			$ 150,300,000
Percentage of net sales in earn-out payment							3.00%	3.00%	3.00%
Net sales minimum limit for royal payment							$ 300,000,000
River Vision [Member] | FDA Approval [Member]
Loss Contingencies [Line Items]
Milestone Payment							100,000,000
Upfront cash payments							100,000,000
Curzion Pharmaceuticals Inc [Member]
Loss Contingencies [Line Items]
Upfront cash payments		$ 45,000,000
Additional payment to be made upon attainment of milestones		$ 15,000,000
RAVICTI, BUPHENYL, PROCYSBI, PENNSAID 2%, DUEXIS, RAYOS, QUINSAIR and UPLIZNA [Member]
Loss Contingencies [Line Items]
Purchase and other commitments outstanding purchase orders							18,700,000
Teprotumumab [Member] | River Vision [Member] | Net Sales Thresholds [Member]
Loss Contingencies [Line Items]
Milestone Payment							225,000,000
AGC Biologics A/S [Member] | TEPEZZA [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment							$ 170,600,000		€ 143.9
Currency exchange rate | $ / €							1.1858				1.1858
Catalent [Member] | TEPEZZA Drug Product [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment							$ 10,200,000
Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment							$ 33,000,000
Supply agreement expiry date							Dec. 31, 2030	Dec. 31, 2030	Dec. 31, 2030
Term of agreement automatically renewal period							3 years	3 years	3 years
Written notice period for termination of agreement							3 years	3 years	3 years
Expected early termination period of agreement due to uncertain event							Jan. 1, 2024	Jan. 1, 2024	Jan. 1, 2024
Purchase commitment outstanding purchase orders							$ 1,600,000
Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Purchase obligation percentage							80.00%	80.00%	80.00%
Boehringer Ingelheim [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Milestone incurred							$ 2,000,000
Boehringer Ingelheim [Member] | ACTIMMUNE Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment							$ 15,200,000
Currency exchange rate | $ / €							1.1858				1.1858
S R One And Lundbeckfond | River Vision [Member]
Loss Contingencies [Line Items]
Percentage of right to receive payments				35.66%
Percentage of remaining net obligations payments				70.25%
Roche [Member]
Loss Contingencies [Line Items]
Currency exchange rate | $ / SFr					1.0382	1.0382	1.0813				1.0813
Milestone Payment | SFr											SFr 103,000,000
Milestone incurred					$ 5,200,000	SFr 5,000,000	$ 46,500,000	SFr 43,000,000
Roche [Member] | TEPEZZA [Member]
Loss Contingencies [Line Items]
Currency exchange rate | $ / SFr							1.0382				1.0382
Milestone incurred					$ 5,200,000	SFr 5,000,000
Roche [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment							9.00%	9.00%	9.00%
Roche [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment							12.00%	12.00%	12.00%
Lundquist Institute [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment							1.00%	1.00%	1.00%
AROXDH [Member]
Loss Contingencies [Line Items]
Upfront cash payment	$ 40,000,000
AROXDH [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Maximum payment to be made upon attainment of milestones	$ 660,000,000
TEPEZZA And KRYSTEXXA [Member]
Loss Contingencies [Line Items]
Advertising commitments							$ 10,700,000

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Remaining Aggregate Potential Milestone Payments Payable Based on Achievement of Net Sales Thresholds (Detail) - River Vision [Member]	Jun. 30, 2021USD ($)
Loss Contingencies [Line Items]
Milestone Payment	$ 325,000,000
Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	225,000,000
TEPEZZA Worldwide Net Sales Threshold >$250 million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	50,000,000
TEPEZZA Worldwide Net Sales Threshold >$375 million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	75,000,000
TEPEZZA Worldwide Net Sales Threshold >$500million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	$ 100,000,000

Share-Based and Long-Term Inc_3

Share-Based and Long-Term Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		Mar. 15, 2021	Feb. 17, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options contractual term					10 years
Aggregate common stock options exercisable				7,395,188		7,129,615
Purchase of ordinary shares were outstanding based on merger agreement	[1]			1,318,053
Tax benefit (detriment) recognized from stock-based compensation expense				$ 60.9	$ 19.3
Pre-tax unrecognized compensation expense for all unvested share-based awards				$ 294.2
Performance Stock Unit Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				150.00%
Performance Stock Unit Awards [Member] | TEPEZZA [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
PSUs outstanding				68,459
Performance Stock Unit Awards [Member] | Relative TSR PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				50.00%		30.00%
Vesting period				3 years		3 years
Performance Stock Unit Awards [Member] | Tech Ops PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				25.00%		70.00%
Performance Stock Unit Awards [Member] | R&D PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				25.00%
Minimum [Member] | Performance Stock Unit Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				0.00%
Maximum [Member] | Performance Stock Unit Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding PSU award vesting amount range				200.00%
Viela [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate common stock options exercisable		2,180,159
Purchase of ordinary shares were outstanding based on merger agreement		1,318,053
Viela [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Conversion Rate		$ 0.60
Viela [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Conversion Rate		$ 1
2020 EIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase to number of ordinary shares authorized			7,000,000
2020 ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized				2,519,726
Common stock shares reserved for future issuance				2,519,726
2020 EIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized				15,929,053
Common stock shares available for grant				15,929,053
2014 Non-Employee Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized				526,895
Common stock shares available for grant				526,895
2018 EIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized				2,328,059
Common stock shares available for grant				2,328,059
[1]	On March 15, 2021, the Company completed its acquisition of Viela.  Under the terms of the merger agreement for Viela, all outstanding Viela stock options assumed by the Company with vesting dates after June 1, 2021, were converted into stock options to purchase the Company’s ordinary shares.  As of March 15, 2021, options previously exercisable for an aggregate of 2,180,159 shares of Viela’s common stock that were converted at a rate of 0.60 to 1 based on the merger agreement, into options to purchase 1,318,053 of the Company’s ordinary shares, were outstanding

Share-Based and Long-Term Inc_4

Share-Based and Long-Term Incentive Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options, Outstanding Beginning Balance		7,129,615
Assumed in acquisition	[1]	1,318,053
Options, Exercised		(993,945)
Options, Forfeited		(58,301)
Options, Expired		(234)
Options, Outstanding Ending Balance		7,395,188	7,129,615
Options, Exercisable as of June 30, 2021		6,602,752
Weighted Average Exercise Price, Outstanding Beginning Balance		$ 21.24
Assumed in acquisition	[1]	41.23
Weighted Average Exercise Price, Exercised		28.11
Weighted Average Exercise Price, Forfeited		45.06
Weighted Average Exercise Price, Expired		17.31
Weighted Average Exercise Price, Outstanding Ending Balance		23.69	$ 21.24
Weighted Average Exercise Price, Exercisable as of June 30, 2021		$ 21.67
Weighted Average Contractual Term Remaining (in years)		4 years 5 months 19 days	4 years 7 months 6 days
Weighted Average Contractual Term Remaining (in years) Exercisable as of June 30,2021		4 years 14 days
Aggregate Intrinsic Value		$ 517,258	$ 370,073
Aggregate Intrinsic Value, Exercisable as of June 30, 2021		$ 475,154
[1]	On March 15, 2021, the Company completed its acquisition of Viela.  Under the terms of the merger agreement for Viela, all outstanding Viela stock options assumed by the Company with vesting dates after June 1, 2021, were converted into stock options to purchase the Company’s ordinary shares.  As of March 15, 2021, options previously exercisable for an aggregate of 2,180,159 shares of Viela’s common stock that were converted at a rate of 0.60 to 1 based on the merger agreement, into options to purchase 1,318,053 of the Company’s ordinary shares, were outstanding

Share-Based and Long-Term Inc_5

Share-Based and Long-Term Incentive Plans - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Outstanding Beginning Balance | shares	5,909,120
Number of Units, Granted | shares	1,991,241
Number of Units, Vested | shares	(2,758,014)
Number of Units, Forfeited | shares	(235,032)
Number of Units, Outstanding Ending Balance | shares	4,907,315
Weighted Average Grant-Date Fair Value Per Unit, Outstanding Beginning Balance | $ / shares	$ 27.87
Weighted Average Grant-Date Fair Value Per Unit, Granted | $ / shares	75.12
Weighted Average Grant-Date Fair Value Per Unit, Vested | $ / shares	23.36
Weighted Average Grant-Date Fair Value Per Unit, Forfeited | $ / shares	59.93
Weighted Average Grant-Date Fair Value Per Unit, Outstanding Ending Balance | $ / shares	$ 48.10

Share-Based and Long-Term Inc_6

Share-Based and Long-Term Incentive Plans - Summary of Performance Stock Unit Awards Activity (Detail) - Performance Stock Unit Awards [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Units, Outstanding Beginning Balance | shares	2,610,924
Number of Units, Granted | shares	450,577
Number of Units, Forfeited | shares	(24,450)
Number of Units, Vested | shares	(2,021,657)
Number of Units, Performance Based Adjustment | shares	512,819	[1]
Number of Units, Outstanding Ending Balance | shares	1,528,213
Weighted Average Grant-Date Fair Value Per Unit, Granted	$ 93.73
Weighted Average Grant-Date Fair Value Per Unit, Forfeited	93.73
Weighted Average Grant-Date Fair Value Per Unit, Vested	21.21
Weighted Average Grant-Date Fair Value Per Unit, Performance Based Adjustment	$ 25.42	[1]
Average Illiquidity discount, Granted	8.64%
Average Illiquidity discount, Forfeited	9.21%
Average Illiquidity discount, Vested	2.66%
Average Illiquidity discount, Performance Based Adjustment	7.27%	[1]
Recorded Weighted Average Fair Value Per Unit, Granted	$ 85.64
Recorded Weighted Average Fair Value Per Unit, Forfeited	85.10
Recorded Weighted Average Fair Value Per Unit, Vested	20.65
Recorded Weighted Average Fair Value Per Unit, Performance Based Adjustment	$ 23.57	[1]
[1]	Represents adjustment based on the net sales performance criteria meeting 162.5% of target as of December 31, 2020 for the 2020 PSUs (as defined below), the net sales performance criteria meeting 200.0% of target as of December 31, 2020 for the TEPEZZA PSUs (as defined below) and meeting total shareholder return (“TSR”) performance at 200.0% for the PSUs that were awarded to key executive participants on January 5, 2018.

Share-Based and Long-Term Inc_7

Share-Based and Long-Term Incentive Plans - Summary of Performance Stock Unit Awards Activity - (Parenthetical) (Detail) - Performance Stock Unit Awards [Member]	Jan. 05, 2018	Dec. 31, 2020
Tech Ops PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of net sales performance criteria met		162.50%
TEPEZZA [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of net sales performance criteria met		200.00%
Key Executive PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of net sales performance criteria met	200.00%

Share-Based and Long-Term Inc_8

Share-Based and Long-Term Incentive Plans - Summary of Significant Valuation Assumptions Related to 2020 PSUs (Detail) - Performance Stock Unit Awards [Member]	6 Months Ended
	Jun. 30, 2021$ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Valuation date stock price	$ 72.54
Expected volatility	45.80%
Risk free rate	0.20%

Share-Based and Long-Term Inc_9

Share-Based and Long-Term Incentive Plans - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 54,424	$ 27,057	$ 115,590	$ 83,478
Cost of Goods Sold [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense			5,080	3,977
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense			17,776	8,928
Selling, General and Administrative Expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense			$ 92,734	$ 70,573

Income Taxes - (Benefit) Expens

Income Taxes - (Benefit) Expense for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income (loss) before (benefit) expense for income taxes	$ 115,633		$ 2,954		$ (55,469)	$ (29,663)
(Benefit) expense for income taxes	(42,484)		82,964		(90,235)	63,938
Net income (loss)	$ 158,117	$ (123,351)	$ (80,010)	$ (13,591)	$ 34,766	$ (93,601)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
(Benefit) expense for income taxes	$ (42,484)	$ 82,964	$ (90,235)	$ 63,938
Anti-hybrid rules, one-time tax provision amount	$ 0	$ 15,200	$ 0	$ 15,200

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - EirGen Pharma Limited [Member] - Subsequent Event [Member] $ in Millions	1 Months Ended
	Jul. 31, 2021USD ($)
Subsequent Event [Line Items]
Subsequent Event, Date	Jul. 31, 2021
Upfront cash payments	$ 64.8