Common Stock - Schedule of Total Stock-Based Compensation Expense Recognized by Type of Award (Parenthetical) (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2017	May 31, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Apr. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Additional stock-based compensation expense			$ 11,852,000	$ 3,301,000	$ 37,770,000	$ 10,742,000
Non-cash adjustments	$ 700,000
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