Equity-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Stock option activity
Outstanding, beginning of the period (in shares)	1,935,106
Options granted (in shares)	165,636	0
Outstanding, end of the period (in shares)	2,100,742
Exercisable (in shares)	942,188
Expected to vest (in shares)	1,158,554
Weighted average exercise price
Outstanding, beginning of period (in dollars per share)	$ 12.37
Options granted (in dollars per share)	23.11
Outstanding, end of the period (in dollars per share)	13.36
Exercisable (in dollars per share)	12.47
Expected to vest (in dollars per share)	$ 14.07
Other disclosures
Remaining contractual life, options outstanding (years)	7 years 8 months 16 days
Remaining contractual life, options exercisable (years)	7 years 6 months 7 days
Remaining contractual life, options expected to vest (years)	7 years 10 months 13 days
Aggregate intrinsic value, options outstanding	$ 15,598
Aggregate intrinsic value, options exercisable	7,829
Aggregate intrinsic value, options expected to vest	$ 7,769