Supplemental Balance Sheet Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease right of use asset (Note 11)	$ 5,099	$ 6,109	$ 6,109
Operating lease liabilities in other current liabilities	1,785		2,459
Operating lease liabilities in other long-term liabilities	3,302		3,657
Total operating lease liabilities	$ 5,087		$ 6,116