Stockholders' Equity - Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares, Options outstanding, Beginning Balance	25,424,437
Number of shares, Options granted	548,667
Number of shares, Options exercised	(4,437,349)
Number of shares, Options forfeited/cancelled	(1,302,135)
Number of shares, Options outstanding, Ending Balance	20,233,620	25,424,437
Number of shares, Options vested and exercisable	3,745,852
Number of shares, Options vested and exercisable and expected to vest thereafter	19,080,337
Weighted average exercise price, Options outstanding, Beginning Balance	$ 3.22
Weighted average exercise price, Options granted	$ 26.77
Weighted average exercise price, Options exercised	$ 1.31
Weighted average exercise price, Options forfeited/cancelled	$ 4.74
Weighted average exercise price, options outstanding, Ending Balance	$ 4.18	$ 3.22
Weighted average exercise price, Options vested and exercisable	$ 2.41
Weighted average exercise price, Options vested and exercisable and expected to vest thereafter	$ 4.16
Weighted average remaining contractual term, Options outstanding	7 years 8 months 12 days	8 years 6 months
Weighted average remaining contractual term, Options vested and exercisable	6 years 8 months 12 days
Weighted average remaining contractual term, Options vested and exercisable and expected to vest thereafter	7 years 8 months 12 days
Aggregate intrinsic value, Options outstanding, Beginning Balance	$ 726,649,586
Aggregate intrinsic value, Options exercised	104,689,345
Aggregate intrinsic value, Options outstanding, Ending Balance	498,862,568	726,649,586
Aggregate intrinsic value, Options vested and exercisable	98,970,347
Aggregate intrinsic value, Options vested and exercisable and expected to vest thereafter	$ 470,900,166