Revenue Components - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		6 Months Ended
	Jul. 16, 2021	Mar. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Pfizer collaboration revenue			$ 25,172	$ 0	$ 54,681	$ 0
Richter
Disaggregation of Revenue [Line Items]
Regulatory milestone payments received	$ 15,000	$ 25,000
Richter license and milestone revenue
Disaggregation of Revenue [Line Items]
Revenues			31,667	0	31,667	33,333
Richter product supply and royalties
Disaggregation of Revenue [Line Items]
Revenues			1,771	$ 0	1,771	0
Richter product supply and royalties | Richter
Disaggregation of Revenue [Line Items]
Revenues			1,700
Richter product supply and royalties | Richter | Maximum
Disaggregation of Revenue [Line Items]
Revenues					$ 100
Revenue Recognized Upon Completion of Delivery | Richter
Disaggregation of Revenue [Line Items]
Revenues			$ 16,700			$ 33,300