Employee Incentive Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Number of Options
Number of options, outstanding beginning of period (in shares)	32,866,862
Number of options, granted (in shares)	2,676,667
Number of options, exercised (in shares)	(9,180,242)
Number of options, canceled (in shares)	(1,446,242)
Number of options, outstanding end of period (in shares)	24,917,045	32,866,862
Vested and expected to vest, number of options (in shares)	24,917,045
Vested and exercisable, number of options (in shares)	10,205,493
Weighted- Average Exercise Price
Options outstanding, weighted average exercise price beginning of period (in dollars per share)	$ 6.01
Options granted, weighted average exercise price (in dollars per share)	11.56
Options exercised, weighted average exercise price (in dollars per share)	3.66
Options canceled, weighted average exercise price (in dollars per share)	7.76
Options outstanding, weighted average exercise price end of period (in dollars per share)	7.37	$ 6.01
Vested and expected to vest, weighted average exercise price (in dollars per share)	7.37
Vested and exercisable, weighted average exercise price (in dollars per share)	$ 5.33
Additional Disclosures
Options outstanding, weighted average remaining contractual term	7 years 7 months 21 days	8 years 2 months 16 days
Options outstanding, aggregate intrinsic value	$ 550,173	$ 145,570
Vested and expected to vest, weighted average remaining contractual term	7 years 7 months 21 days
Vested and exercisable, weighted average remaining contractual term	6 years 10 months 24 days
Vested and expected to vest, aggregate intrinsic value	$ 550,173
Vested and exercisable, aggregate intrinsic value	$ 246,189