Equity-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Stock option activity
Outstanding, beginning of the period (in shares)	1,935,106	2,824,050
Options granted (in shares)	180,539		2,824,050
Options exercised (in shares)	28,000	529,595
Options forfeited (in shares)		359,349
Outstanding, end of the period (in shares)	2,087,645	1,935,106	2,824,050
Exercisable at end of period (in shares)	1,211,044
Expected to vest after end of period (in shares)	876,601
Weighted average exercise price
Outstanding, beginning of period (in dollars per share)	$ 12.37	$ 12.53
Options granted (in dollars per share)	23.65
Options exercised (in dollars per share)	12.31	12.31
Options forfeited (in dollars per share)		12.31
Outstanding, end of the period (in dollars per share)	13.49	$ 12.37	$ 12.53
Exercisable at end of period (in dollars per share)	12.48
Expected to vest after end of period (in dollars per share)	$ 14.88
Other disclosures
Weighted average remaining contractual life, Outstanding	7 years 2 months 23 days	7 years 11 months 23 days
Weighted average remaining contractual life, Exercisable	7 years 7 days
Weighted average remaining contractual life, Expected to vest after end of period	7 years 6 months 7 days
Aggregate intrinsic value, options outstanding	$ 47,336	$ 16,700
Aggregate intrinsic value, options exercisable at end of period	28,681	5,580
Aggregate intrinsic value, options expected to vest after end of period	18,655	11,120
Intrinsic value of stock option awards exercised	$ 580	$ 8,892