Income Taxes - Reconciliation of Benefit from Income Taxes to Amount Computed by Applying Statutory Federal Income Tax Rate to Income (Loss) before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Provision Benefit For Income Taxes [Line Items]
Tax (provision) benefit at federal statutory rate	$ (300)	$ 23,201	$ 22,149
State tax (provision) benefit, net of federal benefit	(1,093)	1,815	2,605
Tax credits, net of valuation allowance	25,153	26,836	21,898
Non-deductible compensation	(7,150)	(4,527)	(2,852)
Non-deductible meals and entertainment	(1,075)	(929)	(727)
Stock-based compensation	780	180	799
Foreign effective tax rate differential, net of valuation allowance	(5,707)	(1,552)	(2,054)
Unremitted subsidiary gains	(2,742)	(1,388)	(864)
Other	(504)	(1,938)	(167)
Total benefit from income taxes	7,915	41,014	35,217
United States [Member]
Provision Benefit For Income Taxes [Line Items]
Change in effective tax rate	567		(5,335)
State [Member]
Provision Benefit For Income Taxes [Line Items]
Change in effective tax rate	$ (14)	$ (684)	$ (235)