Segments - Reconciliation of Net Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Reconciliation of Adjusted EBITDA to Net income
Net income (loss)	$ 14,273	$ 8,226	$ 17,224	$ 9,163	$ 8,940	$ (2,212)	$ 2,825	$ 3,011	$ 48,886	$ 12,564	$ (11,697)
Income tax expense (benefit)									22,654	12,584	(6,626)
Depreciation expense									25,565	26,667	32,208
Amortization expense									43,675	37,548	31,957
EBITDA									177,091	125,853	81,228
(Gain) loss on disposal of assets									(338)	(645)	1,089
Management fee to related party									188	2,250	2,250
Interest rate swap and cap mark-to-market									382	19	2,494
Operating Segment
Reconciliation of Adjusted EBITDA to Net income
Adjusted EBITDA									188,229	138,183	105,796
Reconciling items
Reconciliation of Adjusted EBITDA to Net income
Interest expense									36,463	37,418	36,396
Interest income									(152)	(928)	(1,010)
Stock appreciation rights expense									(148)	(1,988)	(2,268)
Redeemable noncontrolling interests									(3,536)	(880)	(1,859)
Equity-based compensation									2,534	2,699	6,455
Severance and other permitted costs									(157)	379	413
Transaction costs (acquisitions and other)									2,249	3,751	2,728
Effects of fair value adjustments to inventory									946	1,009	5,012
Secondary public offering costs									1,385
Debt transaction costs									265
EBITDA add-backs									$ 11,138	$ 12,330	$ 24,568