Equity-Based Compensation - Restricted Stock Units (Details) - Restricted Stock Units $ / shares in Units, $ in Millions	9 Months Ended
	Jan. 31, 2018 USD ($) $ / shares shares
Restricted stock units granted to employees (in shares) | shares	21,766
Vesting period (in years)	3 years
Fair value on grant date (in dollars per share) | $ / shares	$ 37.49
Unrecognized compensation cost | $	$ 0.7
Weighted-average period for recognition of unrecognized compensation expense (in years)	2 years 9 months 18 days