Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Contingency [Line Items]
Valuation allowance	$ 47,076,000	$ 42,621,000
Impact on effective tax rate	84,000,000.0
Accrued interest or penalties associated with uncertain tax positions	0	$ 0
United States [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 687,100,000
Operating loss carryforwards expiration beginning year	2022
Tax years subject to examination	2018 and thereafter
United States [Member] | Research & Development [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward amount	$ 214,200,000
United States [Member] | Research & Development [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards expiration beginning year	2026
State [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 560,100,000
Operating loss carryforwards expiration beginning year	2022
Tax years subject to examination	2018 and thereafter
State [Member] | Research & Development [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward amount	$ 174,600,000
State [Member] | Research & Development [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards expiration beginning year	2022
Foreign [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward amount	$ 1,900,000
Tax years subject to examination	2017 and thereafter
Foreign [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards expiration beginning year	2022