Segments - Reconciliation of Net Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Segment Reporting [Abstract]
Net income	$ 33,746	$ 16,126	$ 28,469	$ 27,219	$ (41,456)	$ 10,879	$ 29,138	$ 24,820	$ 105,560	$ 23,381	$ 56,002
Interest expense									53,786	67,718	73,677
Write-off of debt discount and deferred financing fees									4,606	1,331	0
Interest income									(86)	(88)	(66)
Provision for income taxes									31,534	22,944	14,039
Depreciation expense									50,480	51,332	46,456
Amortization expense									57,645	65,201	71,003
Impairment of goodwill					63,100				0	63,074	0
Stock appreciation expense									3,173	1,572	2,730
Redeemable noncontrolling interests									1,288	520	1,188
Equity-based compensation									8,442	7,060	3,906
Severance and other permitted costs									2,948	5,733	8,152
Transaction costs (acquisitions and other)									1,068	2,414	7,858
(Gain) loss on disposal and impairment of assets									(1,011)	658	(525)
Effects of fair value adjustments to inventory									788	575	4,176
Change in fair value of financial instruments									0	0	6,395
Gain on legal settlement					$ (14,000)				(1,382)	(14,029)	0
Secondary public offering costs									0	363	0
Debt transaction costs									532	0	678
Adjusted EBITDA									$ 319,371	$ 299,759	$ 295,669