Segments - Reconciliation of Net Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Segments
Adjusted EBITDA	$ 54,245	$ 49,519	$ 106,994	$ 95,460
Interest expense	(7,917)	(7,154)	(15,417)	(14,731)
Write-off of debt discount and deferred financing fees		(1,466)	(74)	(6,892)
Interest income	26	35	49	78
Income tax expense	(9,983)	(710)	(20,043)	(6,869)
Depreciation expense	(6,023)	(6,548)	(12,013)	(12,930)
Amortization expense	(10,690)	(10,820)	(21,045)	(20,233)
Stock appreciation (expense) or income	(642)	144	(1,232)	236
Redeemable noncontrolling interests	(164)	(2,531)	(1,030)	(2,823)
Equity-based compensation	(375)	(686)	(847)	(1,359)
Severance and other permitted costs	(113)	(118)	(317)	(258)
Transaction costs (acquisitions and other)	(88)	(1,827)	(246)	(2,481)
Gain (loss) on sale of assets	207	(68)	597	130
Management fee to related party				(188)
Effects of fair value adjustments to inventory	(187)	(457)	(187)	(621)
Interest rate cap mark-to-market	(238)	(89)	(434)	(132)
Secondary public offering costs			(631)
Debt transaction costs	(35)		(758)
Net income	$ 18,023	$ 17,224	$ 33,366	$ 26,387