Segments - Reconciliation of Adjusted EBITDA to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Apr. 30, 2016
Reconciliation of Adjusted EBITDA to Net income
Interest expense	$ (8,620)	$ (9,260)	$ (21,623)	$ (18,517)
Interest income	35	208	78	438
Income tax expense	(710)	(2,623)	(6,869)	(5,478)
Depreciation expense	(6,548)	(6,465)	(12,930)	(13,738)
Amortization expense	(10,820)	(8,797)	(20,233)	(17,589)
Stock appreciation rights expense	144	(692)	236	(1,286)
Redeemable noncontrolling interests	(2,531)	(451)	(2,823)	(1,005)
Equity-based compensation	(686)	(863)	(1,359)	(1,361)
(Loss) gain on disposal of assets	(68)	(305)	130	(280)
Management fee to related party		(563)	(188)	(1,125)
Net income	17,224	2,825	26,387	5,836	$ 12,564
Operating Segment
Reconciliation of Adjusted EBITDA to Net income
Adjusted EBITDA	49,519	34,800	95,460	68,913
Reconciling items
Reconciliation of Adjusted EBITDA to Net income
Severance and other permitted costs	(118)	(824)	(258)	(1,381)
Transaction costs (acquisitions and other)	(1,827)	$ (1,340)	(2,481)	$ (1,755)
Effects of fair value adjustments to inventory	(457)		(621)
Interest rate cap mark-to-market	$ (89)		$ (132)