Equity-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016
Stock option activity
Outstanding, beginning of the period (in shares)	1,935,106
Options granted (in shares)	170,539	0
Outstanding, end of the period (in shares)	2,105,645
Exercisable (in shares)	1,090,610
Expected to vest (in shares)	1,015,035
Weighted average exercise price
Outstanding, beginning of period (in dollars per share)	$ 12.37
Options granted (in dollars per share)	23.04
Outstanding, end of the period (in dollars per share)	13.37
Exercisable (in dollars per share)	12.47
Expected to vest (in dollars per share)	$ 14.34
Other disclosures
Remaining contractual life, options outstanding (years)	7 years 5 months 16 days
Remaining contractual life, options exercisable (years)	7 years 3 months 4 days
Remaining contractual life, options expected to vest (years)	7 years 8 months 1 day
Aggregate intrinsic value, options outstanding	$ 34,675
Aggregate intrinsic value, options exercisable	18,942
Aggregate intrinsic value, options expected to vest	$ 15,733