Equity-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Apr. 30, 2018
Other disclosures
Equity-based compensation	$ 404	$ 473
Selling, general and administrative expenses
Other disclosures
Equity-based compensation	$ 400	$ 500
Stock Options
Number of Options
Outstanding, beginning of the period (in shares)	1,952
Options granted (in shares)	0	0
Options exercised (in shares)	(35)	0
Options forfeited (in shares)	(2)
Outstanding, end of the period (in shares)	1,915		1,952
Exercisable at end of period (in shares)	1,701
Vested and expected to vest at end of period (in shares)	1,910
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)	$ 14.37
Options exercised (in dollars per share)	12.31
Options forfeited (in dollars per share)	37.49
Outstanding, end of the period (in dollars per share)	14.39		$ 14.37
Exercisable at end of period (in dollars per share)	13.04
Vested and expected to vest at end of period (in dollars per share)	$ 14.35
Other disclosures
Weighted Average Remaining Contractual Life, Outstanding (in years)	6 years 4 months 10 days		6 years 6 months 7 days
Weighted Average Remaining Contractual Life, Exercisable at end of period (in years)	6 years 1 month 24 days
Weighted Average Remaining Contractual Life, Vested and expected to vest at end of period (in years)	6 years 4 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 25,046		$ 33,209
Aggregate Intrinsic Value, Exercisable at end of period	23,907
Aggregate Intrinsic Value, Vested and expected to vest at end of period	25,030
Intrinsic value of options exercised	500
Unrecognized compensation cost	$ 900
Weighted-average period for recognition of unrecognized compensation expense (in years)	2 years