Collaboration and License Agreements - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands		6 Months Ended
	Dec. 26, 2020	Sep. 30, 2022	Mar. 31, 2022
Deferred Revenue
Deferred revenue, current		$ 117,231	$ 100,564
Deferred revenue, non-current		379,321	375,706
Cost Cash Advance from Collaboration Partner
Beginning balance		33,818
Additions	$ 146,400	0
Imputed Interest		568
Deductions		(34,386)
Ending balance		0
Cost share advance from collaboration partner, current		0	33,818
Collaboration expense to Pfizer
Deferred Revenue
Beginning balance		476,270
Additions		100,000
Imputed Interest		0
Deductions		(79,718)
Ending balance		496,552
Deferred revenue, current		117,200	100,600
Deferred revenue, non-current		$ 379,300	$ 375,700