Segments - Reconciliation of Adjusted EBITDA to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016	Apr. 30, 2016
Reconciliation of Adjusted EBITDA to Net income
Interest expense	$ (7,431)	$ (9,473)	$ (22,162)	$ (27,990)
Write-off of debt discount and deferred financing fees	(211)		(7,103)
Interest income	23	247	101	685
Income tax (expense) benefit	(5,363)	819	(12,232)	(4,659)
Depreciation expense	(6,465)	(6,469)	(19,395)	(20,207)
Amortization expense	(11,851)	(9,540)	(32,084)	(27,129)
Stock appreciation rights expense	498	(337)	734	(1,623)
Redeemable noncontrolling interests	(256)	(167)	(3,079)	(1,172)
Equity-based compensation	(622)	(728)	(1,981)	(2,089)
(Loss) gain on disposal of assets	114	205	244	(75)
Management fee to related party		(562)	(188)	(1,687)
Net income (loss)	8,227	(2,212)	34,614	3,624	$ 12,564
Operating Segment
Reconciliation of Adjusted EBITDA to Net income
Adjusted EBITDA	40,678	25,688	136,138	94,601
Reconciling items
Reconciliation of Adjusted EBITDA to Net income
Severance and other permitted costs	(57)	(52)	(315)	(1,433)
Transaction costs (acquisitions and other)	(566)	(1,057)	(3,047)	(2,812)
Effects of fair value adjustments to inventory	(155)	$ (786)	(776)	$ (786)
Interest rate cap mark-to-market	$ (109)		$ (241)