Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	3 Months Ended		7 Months Ended	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Mar. 15, 2018	Oct. 31, 2017	Oct. 31, 2016	Mar. 31, 2017	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding on behalf of employees for future purchases	$ 2,726			$ 2,726			$ 0
Stock-based compensation expense	$ 5,937	$ 2,517		$ 15,002	$ 6,316
Shares committed under 2017 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)						1,500,000
Number of shares authorized, annual increase						2,500,000
Number of shares authorized, annual increase, percentage of outstanding shares at the end of prior fiscal year						1.00%
Maximum payroll deduction (as a percent of eligible compensation)				15.00%
Purchase price of common stock (as a percent)				85.00%
Number of shares purchased under plan (in shares)	0			0
Stock-based compensation expense				$ 900
Unrecognized compensation cost	$ 700			$ 700
Unrecognized compensation cost, period for recognition				4 months 24 days
Shares committed under 2017 ESPP | Forecast
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased under plan (in shares)			493,564