Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Basic Net Income Per Share
Net income	$ 98,874	$ 12,684	$ 3,839	$ (1,709)	$ 3,622	$ 4,393	$ 1,059	$ (1,723)	$ 113,688	$ 7,351	$ 15,014
Weighted average shares used in computing basic net income per share									40,632	39,334	39,113
Net income per share-basic	$ 2.40	$ 0.31	$ 0.09	$ (0.04)	$ 0.09	$ 0.11	$ 0.03	$ (0.04)	$ 2.80	$ 0.19	$ 0.38
Diluted Net Income Per Share
Net income	$ 98,874	$ 12,684	$ 3,839	$ (1,709)	$ 3,622	$ 4,393	$ 1,059	$ (1,723)	$ 113,688	$ 7,351	$ 15,014
Weighted average shares used in computing basic net income per share									40,632	39,334	39,113
Effect of dilutive securities									2,226	2,272	1,939
Weighted average shares used in computing diluted net income per share									42,858	41,606	41,052
Net income per share-diluted	$ 2.24	$ 0.30	$ 0.09	$ (0.04)	$ 0.09	$ 0.11	$ 0.03	$ (0.04)	$ 2.65	$ 0.18	$ 0.37