Collaboration and License Agreements - Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Deferred Revenue
Deferred revenue, current	$ 100,564	$ 100,564
Deferred revenue, non-current	375,706	397,369
Cost Cash Advance from Collaboration Partner
Beginning balance	121,862	0
Additions	0	146,384
Imputed Interest	2,413	635
Deductions	(90,457)	(25,157)
Ending balance	33,818	121,862
Cost share advance from collaboration partner, current	33,818	92,415
Cost share advance from Pfizer, non-current	0	29,447
Collaboration expense to Pfizer
Deferred Revenue
Beginning balance	497,933	40,000
Additions	100,000	513,620
Imputed Interest	0	0
Deductions	(121,663)	(55,687)
Ending balance	$ 476,270	$ 497,933