Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Basic Net Income Per Share
Net income	$ 14,899	$ 15,432	$ 8,875	$ 12,910	$ 10,998	$ 10,555	$ 7,735	$ 8,859	$ 52,116	$ 38,147	$ 113,688
Weighted average shares used in computing basic net income per share									43,238	42,204	40,632
Net income per share - basic	$ 0.34	$ 0.36	$ 0.21	$ 0.30	$ 0.26	$ 0.25	$ 0.18	$ 0.21	$ 1.21	$ 0.90	$ 2.80
Diluted Net Income Per Share
Net income	$ 14,899	$ 15,432	$ 8,875	$ 12,910	$ 10,998	$ 10,555	$ 7,735	$ 8,859	$ 52,116	$ 38,147	$ 113,688
Weighted average shares used in computing basic net income per share									43,238	42,204	40,632
Effect of dilutive securities									1,420	2,691	2,226
Weighted average shares used in computing diluted net income per share									44,658	44,895	42,858
Net income per share - diluted	$ 0.33	$ 0.34	$ 0.20	$ 0.29	$ 0.24	$ 0.23	$ 0.17	$ 0.20	$ 1.17	$ 0.85	$ 2.65