Net Loss Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Numerator
Net loss	$ (13,693)	$ (4,575)	$ (29,827)	$ (25,045)
Denominator:
Weighted-average common shares outstanding (in shares)	104,181	95,798	103,160	62,798
Less: Weighted-average unvested common shares subject to repurchase or forfeiture (in shares)	(81)	(280)	(85)	(332)
Weighted-average shares used to compute net loss per share, basic and diluted (in shares)	104,100	95,518	103,075	62,466
Net loss per share
Net loss per share, basic and diluted (in dollars per share)	$ (0.13)	$ (0.05)	$ (0.29)	$ (0.40)