Computation of Basic and Diluted Net Income Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Basic Net Income (Loss) Per Share
Net income (loss)	$ 5,469	$ 601	$ 8,588	$ (3,993)
Weighted average shares used in computing basic net income (loss) per share	39,431	38,256	39,288	38,081
Net income (loss) per share - basic	$ 0.14	$ 0.02	$ 0.22	$ (0.10)
Diluted Net Income (Loss) Per Share
Net income (loss)	$ 5,469	$ 601	$ 8,588	$ (3,993)
Weighted average shares used in computing basic net income (loss) per share	39,431	38,256	39,288	38,081
Effect of dilutive securities	2,291	1,110	2,357
Weighted average shares used in computing diluted net income (loss) per share	41,722	39,366	41,645	38,081
Net income (loss) per share - diluted	$ 0.13	$ 0.02	$ 0.21	$ (0.10)