Common Stock - Schedule of Total Stock-Based Compensation Expense Recognized by Type of Award (Parenthetical) (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Apr. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Additional stock-based compensation expense		$ 22,453,000	$ 3,643,000	$ 25,918,000	$ 7,441,000
Eligible Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Outstanding and unexercised stock option exercise price	$ 13.68
Eligible options shares of common stock repriced	3,291,783
Eligible options repriced common stock weighted average exercise price	$ 24.31
Additional stock-based compensation expense	$ 2,600	$ 7,300
Minimum
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Outstanding and unexercised stock option exercise price						$ 13.68