Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Accrued R&D expenses	$ 8,544	$ 15,500
Accrued compensation-related expenses	20,571	9,309
Accrued commercial expenses	7,770	818
Accrued sales discounts, rebates, and allowances	1,315	0
Accrued professional service fees	935	1,126
Accrued other expenses and tax obligations	5,315	2,307
Accrued expenses and other current liabilities	44,612	29,060
Product revenue, net
Disaggregation of Revenue [Line Items]
Deferred revenue	$ 162	$ 0