Income Taxes - Components of (loss) Income Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Provision Benefit For Income Taxes [Line Items]
(Loss) income before income taxes	$ (110,481)	$ (105,470)	$ 25,384
United States [Member]
Provision Benefit For Income Taxes [Line Items]
(Loss) income before income taxes	(102,643)	(92,767)	29,649
Foreign [Member]
Provision Benefit For Income Taxes [Line Items]
(Loss) income before income taxes	$ (7,838)	$ (12,703)	$ (4,265)