Common Stock (Details) (USD $)	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Common Stock
Number of shares of common stock authorized	1,000,000,000	106,511,960
Common stock, par value per share (in dollars per share)	$ 0.001	$ 0.001
Shares of common stock issued	100,920,350	23,092,407
Common stock, shares issued and outstanding	100,920,350	23,092,407
Early Exercise of Employee Options
Shares of restricted common stock, subject to a repurchase right	93,750	411,318
Portion of shares from early exercises of employee options for which the repurchase right lapses on the first anniversary of the vesting start date.	0.25	0.25
Portion of shares from early exercises of employee options for which the repurchase right lapses on monthly basis after the first anniversary of the vesting start date.	0.02	0.02