Equity-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2017	Apr. 30, 2017
Stock option activity
Outstanding, beginning of the period (in shares)	2,087,645
Options granted (in shares)	0
Outstanding, end of the period (in shares)	2,087,645	2,087,645
Exercisable at end of period (in shares)	1,400,875
Expected to vest after end of period (in shares)	686,770
Weighted average exercise price
Outstanding, beginning of period (in dollars per share)	$ 13.49
Outstanding, end of the period (in dollars per share)	13.49	$ 13.49
Exercisable at end of period (in dollars per share)	12.79
Expected to vest after end of period (in dollars per share)	$ 14.90
Other disclosures
Weighted average remaining contractual life, Outstanding	6 years 11 months 19 days	7 years 2 months 23 days
Weighted average remaining contractual life, Exercisable	6 years 9 months 29 days
Weighted average remaining contractual life, Expected to vest after end of period	7 years 3 months 7 days
Aggregate intrinsic value, options outstanding	$ 34,518	$ 47,336
Aggregate intrinsic value, options exercisable at end of period	24,135
Aggregate intrinsic value, options expected to vest after end of period	$ 10,383