Certain Transactions - Other Transactions - Additional Information (Detail) - USD ($) $ in Millions			1 Months Ended	3 Months Ended			6 Months Ended	12 Months Ended
	Jan. 08, 2018	May 12, 2017	Sep. 30, 2016	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2016	Jun. 30, 2021	Dec. 31, 2018	Dec. 31, 2017
Alder [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment	$ 25
Milestone payment					$ 25
Collaborative agreement milestone payments	$ 150
Otsuka [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment		$ 50
Milestone payment				$ 15
Celltrion [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Refundable payment							$ 60
Total associated cost							160
Regeneron [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment						$ 250
Collaborative agreement milestone payments			$ 2,230					$ 120	$ 120
Research and development costs			$ 1,000
Alvotech [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Collaborative agreement milestone payments							$ 450