Computation of Net Income (Loss) per Common Share - Reconciliation of Numerators and Denominators of EPS Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income (loss)	$ 22,558	$ (7,281)	$ 17,821	$ (22,533)
Denominator:
Weighted-average shares of common stock outstanding (in shares)	21,252	19,531	21,126	18,316
Weighted-average shares subject to repurchase (in shares)	(939)	(471)	(886)	(391)
Shares used in per-share calculation ― basic (in shares)	20,313	19,060	20,240	17,925
Shares used in per-share calculation ― diluted (in shares)	20,581	19,060	20,560	17,925
Net income (loss) per share ― basic (in dollars per share)	$ 1.11	$ (0.38)	$ 0.88	$ (1.26)
Net income (loss) per share ― diluted (in dollars per share)	$ 1.10	$ (0.38)	$ 0.87	$ (1.26)