Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Basic Net Income Per Share
Net income	$ 13,446	$ 15,432	$ 75,323	$ 37,217
Weighted average shares used in computing basic net income per share	44,247	43,431	44,095	43,125
Net income per share - basic	$ 0.30	$ 0.36	$ 1.71	$ 0.86
Diluted Net Income Per Share
Net income	$ 13,446	$ 15,432	$ 75,323	$ 37,217
Weighted average shares used in computing basic net income per share	44,247	43,431	44,095	43,125
Effect of dilutive securities	1,622	1,339	1,636	1,472
Weighted average shares used in computing diluted net income per share	45,869	44,770	45,731	44,597
Net income per share - diluted	$ 0.29	$ 0.34	$ 1.65	$ 0.83