Computation of Basic and Diluted Net Income Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Basic Net Income (Loss) Per Share
Net income (loss)	$ 3,742	$ 2,684	$ 5,469	$ 3,119	$ 2,567	$ 2,921	$ 601	$ (4,594)	$ 15,014	$ 1,495	$ (11,755)
Weighted average shares used in computing basic net income (loss) per share									39,113	38,374	37,167
Net income (loss) per share-basic	$ 0.10	$ 0.07	$ 0.14	$ 0.08	$ 0.07	$ 0.08	$ 0.02	$ (0.12)	$ 0.38	$ 0.04	$ (0.32)
Diluted Net Income (Loss) Per Share
Net income (loss)	$ 3,742	$ 2,684	$ 5,469	$ 3,119	$ 2,567	$ 2,921	$ 601	$ (4,594)	$ 15,014	$ 1,495	$ (11,755)
Weighted average shares used in computing basic net income (loss) per share									39,113	38,374	37,167
Effect of dilutive securities									1,939	1,798
Weighted average shares used in computing diluted net income (loss) per share									41,052	40,172	37,167
Net income (loss) per share-diluted	$ 0.09	$ 0.07	$ 0.13	$ 0.08	$ 0.06	$ 0.07	$ 0.02	$ (0.12)	$ 0.37	$ 0.04	$ (0.32)