Stockholders' Equity - Summary of Stock Option Activity (Detail)	9 Months Ended	12 Months Ended
	Oct. 31, 2016 USD ($) $ / shares shares	Jan. 31, 2016 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares, Options outstanding, Beginning Balance | shares	18,549,702
Number of shares, Options granted | shares	1,265,000
Number of shares, Options exercised | shares	(2,537,421)
Number of shares, Options forfeited/cancelled | shares	(232,919)
Number of shares, Options outstanding, Ending Balance | shares	17,044,362	18,549,702
Number of shares, Options vested and exercisable | shares	5,673,711
Number of shares, Options vested and exercisable and expected to vest thereafter | shares	16,439,091
Weighted average exercise price, Options outstanding, Beginning Balance | $ / shares	$ 5.01
Weighted average exercise price, Options granted | $ / shares	27.51
Weighted average exercise price, Options exercised | $ / shares	3.15
Weighted average exercise price, Options forfeited/cancelled | $ / shares	4.34
Weighted average exercise price, options outstanding, Ending Balance | $ / shares	6.97	$ 5.01
Weighted average exercise price, Options vested and exercisable | $ / shares	5.06
Weighted average exercise price, Options vested and exercisable and expected to vest thereafter | $ / shares	$ 6.90
Weighted average remaining contractual term, Options outstanding	6 years 6 months	6 years 9 months 18 days
Weighted average remaining contractual term, Options vested and exercisable	5 years 10 months 24 days
Weighted average remaining contractual term, Options vested and exercisable and expected to vest thereafter	6 years 6 months
Aggregate intrinsic value, Options outstanding | $	$ 543,566,597	$ 359,306,108
Aggregate intrinsic value, Options vested and exercisable | $	191,721,450
Aggregate intrinsic value, Options vested and exercisable and expected to vest thereafter | $	$ 525,406,590