Acquisitions, Divestitures and Other Arrangements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended			12 Months Ended
	Dec. 15, 2021	Mar. 15, 2021	Jan. 02, 2020	Jul. 31, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2021	Jul. 16, 2019
Business Acquisition [Line Items]
Total consideration					$ 336,804	$ 328,202		$ 328,202
Upfront cash payments					14,198		$ 18,333
Outstanding principal amount					2,602,026	2,606,026		2,606,026	$ 625,000
Acquisition-related costs					$ 1,589		49,391
Net reduction in goodwill								9,700
Viela Bio [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement		Mar. 15, 2021
Share price					$ 53.00
Outstanding principal amount		$ 1,600,000
Total consideration for acquisition		3,000,000			$ 2,994,091
Cash acquired from acquisition		$ 342,300			$ 342,300
Acquisition-related costs								28,600
Net reduction in goodwill								9,700
Acquisition-date fair value at a discount rate					11.50%
Finite-lived intangible assets, remaining amortization period					14 years
Deferred tax liability rate					23.80%
Deferred tax liability					$ 451,300
Viela Bio [Member] | Acquisition Related Costs [Member]
Business Acquisition [Line Items]
Net income, Pro forma			$ 86,100
Viela Bio [Member] | Research and Development [Member]
Business Acquisition [Line Items]
Acquisition-date fair value at a discount rate					12.50%
Viela Bio [Member] | Ordinary Shares [Member]
Business Acquisition [Line Items]
Share price		$ 53.00
UPLIZNA [Member]
Business Acquisition [Line Items]
Inventory, raw materials					$ 10,100		2,300
Inventory, work in Process, gross					119,000		1,900
Inventory, net					149,300		151,600
Inventory, finished goods, gross					20,200		400
Inventory step-up expense					27,200		$ 900
Alpine [Member]
Business Acquisition [Line Items]
Upfront cash payments					$ 25,000	15,000
Payment for acquisition of IPR&D asset								28,100
Maximum amount eligible to receive per program	$ 381,000
Total future success-based payments related to development, regulatory and commercial milestones	$ 1,520,000
Alpine [Member] | Upfront Payment
Business Acquisition [Line Items]
Business acquisition, costs								25,000
Alpine [Member] | Premium Paid For Common Stock
Business Acquisition [Line Items]
Business acquisition, costs								3,100
Alpine [Member] | Other Assets [Member]
Business Acquisition [Line Items]
Business acquisition, asset						11,900		11,900
Alpine [Member] | Private Placement [Member]
Business Acquisition [Line Items]
Purchase of common stock shares	951,980
Alpine [Member] | Research and Development [Member]
Business Acquisition [Line Items]
Business acquisition, costs						$ 28,100
Arrowhead Pharmaceuticals [Member]
Business Acquisition [Line Items]
Upfront cash payments				$ 40,000
Potential additional contingent consideration payment				660,000
Upfront cash payment								$ 40,000
EirGen Pharma Limited [Member]
Business Acquisition [Line Items]
Total consideration				67,900
Upfront cash payments				64,800
Additional transaction cost				$ 3,100