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, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Basic Net Income Per Share
Net income	$ 10,998	$ 10,555	$ 7,735	$ 8,859	$ 98,874	$ 12,684	$ 3,839	$ (1,709)	$ 38,147	$ 113,688	$ 7,351
Weighted average shares used in computing basic net income per share									42,204	40,632	39,334
Net income per share - basic	$ 0.26	$ 0.25	$ 0.18	$ 0.21	$ 2.40	$ 0.31	$ 0.09	$ (0.04)	$ 0.90	$ 2.80	$ 0.19
Diluted Net Income Per Share
Net income	$ 10,998	$ 10,555	$ 7,735	$ 8,859	$ 98,874	$ 12,684	$ 3,839	$ (1,709)	$ 38,147	$ 113,688	$ 7,351
Weighted average shares used in computing basic net income per share									42,204	40,632	39,334
Effect of dilutive securities									2,691	2,226	2,272
Weighted average shares used in computing diluted net income per share									44,895	42,858	41,606
Net income per share - diluted	$ 0.24	$ 0.23	$ 0.17	$ 0.20	$ 2.24	$ 0.30	$ 0.09	$ (0.04)	$ 0.85	$ 2.65	$ 0.18