Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic Net Income Per Share
Net income	$ 24,503	$ 8,875	$ 61,877	$ 21,785
Weighted average shares used in computing basic net income per share	44,141	43,129	44,018	42,971
Net income per share - basic	$ 0.56	$ 0.21	$ 1.41	$ 0.51
Diluted Net Income Per Share
Net income	$ 24,503	$ 8,875	$ 61,877	$ 21,785
Weighted average shares used in computing basic net income per share	44,141	43,129	44,018	42,971
Effect of dilutive securities	1,557	1,451	1,637	1,522
Weighted average shares used in computing diluted net income per share	45,698	44,580	45,655	44,493
Net income per share - diluted	$ 0.54	$ 0.20	$ 1.36	$ 0.49