Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares, Options outstanding, Beginning Balance	20,233,620
Number of shares, Options granted	619,800
Number of shares, Options exercised	(2,034,581)
Number of shares, Options forfeited/cancelled	(269,137)
Number of shares, Options outstanding, Ending Balance	18,549,702	20,233,620
Number of shares, Options vested and exercisable	5,359,310
Number of shares, Options vested and exercisable and expected to vest thereafter	17,784,060
Weighted average exercise price, Options outstanding, Beginning Balance	$ 4.18
Weighted average exercise price, Options granted	26.91
Weighted average exercise price, Options exercised	2.90
Weighted average exercise price, Options forfeited/cancelled	9.04
Weighted average exercise price, options outstanding, Ending Balance	5.01	$ 4.18
Weighted average exercise price, Options vested and exercisable	3.51
Weighted average exercise price, Options vested and exercisable and expected to vest thereafter	$ 5.00
Weighted average remaining contractual term, Options outstanding	6 years 9 months 18 days	7 years 8 months 12 days
Weighted average remaining contractual term, Options vested and exercisable	6 years 1 month 6 days
Weighted average remaining contractual term, Options vested and exercisable and expected to vest thereafter	6 years 9 months 18 days
Aggregate intrinsic value, Options outstanding, Beginning Balance	$ 498,862,568
Aggregate intrinsic value, Options outstanding, Ending Balance	359,306,108	$ 498,862,568
Aggregate intrinsic value, Options vested and exercisable	111,640,103
Aggregate intrinsic value, Options vested and exercisable and expected to vest thereafter	$ 344,779,212