Collaboration and License Agreements - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2021	Mar. 31, 2021
Deferred Revenue
Deferred revenue, current	$ 100,564	$ 100,564
Deferred revenue, non-current	400,849	397,369
Cost Cash Advance from Collaboration Partner
Beginning balance	121,862
Additions	0
Imputed Interest	1,818
Deductions	(68,654)
Ending balance	55,026
Cost share advance from collaboration partner, current	55,026	92,415
Cost share advance from Pfizer, non-current	0	29,447
Collaboration expense to Pfizer
Deferred Revenue
Beginning balance	497,933
Additions	100,000
Imputed Interest	0
Deductions	(96,520)
Ending balance	501,413
Deferred revenue, current	100,600	100,600
Deferred revenue, non-current	$ 400,800	$ 397,400