Employee Incentive Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Apr. 30, 2018	Jan. 31, 2018
Number of Options
Number of options, outstanding beginning of period (in shares)	24,917,045
Number of options, granted (in shares)	684,500
Number of options, exercised (in shares)	(2,461,383)
Number of options, canceled (in shares)	(464,669)
Number of options, outstanding end of period (in shares)	22,675,493	24,917,045
Vested and exercisable, number of options (in shares)	9,285,314
Weighted- Average Exercise Price
Options outstanding, weighted average exercise price beginning of period (in dollars per share)	$ 7.37
Options granted, weighted average exercise price (in dollars per share)	39.21
Options exercised, weighted average exercise price (in dollars per share)	4.95
Options canceled, weighted average exercise price (in dollars per share)	8.24
Options outstanding, weighted average exercise price end of period (in dollars per share)	8.58	$ 7.37
Vested and exercisable, weighted average exercise price (in dollars per share)	$ 5.81
Additional Disclosures
Options outstanding, weighted average remaining contractual term	7 years 8 months 5 days	7 years 7 months 21 days
Options outstanding, aggregate intrinsic value	$ 776,287	$ 550,173
Vested and exercisable, weighted average remaining contractual term	6 years 10 months 24 days
Vested and exercisable, aggregate intrinsic value	$ 343,540