Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended		9 Months Ended		11 Months Ended
	Oct. 31, 2018	Apr. 30, 2018	Oct. 31, 2017	Mar. 15, 2019	Sep. 17, 2018	Oct. 31, 2018	Oct. 31, 2017	Mar. 15, 2018	Feb. 01, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under employee stock purchase plan	$ 2,687	$ 4,091				$ 6,778
Stock-based compensation expense	$ 12,922		$ 5,937			$ 31,943	$ 15,002
Shares committed under 2017 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized, annual increase (in shares)									939,769	2,500,000
Number of shares authorized, annual increase, percentage of outstanding shares at the end of prior fiscal year										1.00%
Number of shares authorized (in shares)	1,746,085					1,746,085
Issuance of common stock under employee stock purchase plans (in shares)								437,527
Shares purchased under plan (in dollars per share)					$ 10.49			$ 9.35
Issuance of common stock under employee stock purchase plan					$ 2,700			$ 4,100
Number of shares purchased under plan (in shares)					256,157
Common stock withheld on behalf of employees for future purchases under the ESPP	900,000					900,000
Expected life (years)		6 months	0 years			6 months	11 months 1 day
Expected volatility	45.09%		0.00%				38.30%
Expected volatility, minimum						34.41%
Expected volatility, maximum						45.09%
Dividend yield		0.00%	0.00%			0.00%	0.00%
Risk-free rate	2.35%		0.00%				1.02%
Risk-free rate, minimum						1.95%
Risk-free rate, maximum						2.35%
Stock-based compensation expense	$ 500					$ 1,500
Unrecognized compensation cost	$ 900					$ 900
Unrecognized compensation cost, period for recognition						4 months 13 days
Maximum payroll deduction (as a percent of eligible compensation)						15.00%
Purchase price of common stock (as a percent)						85.00%
Scenario, Forecast | Shares committed under 2017 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased under plan (in shares)				179,221