Intangibles (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Apr. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 12,000	$ 12,300	$ 36,500	$ 36,800
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangibles, gross	274,000		274,000		$ 274,000
Less accumulated amortization	(140,806)		(140,806)		(106,556)
Intangibles, net	133,194		133,194		167,444
Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangibles, gross	10,000		10,000		10,000
Less accumulated amortization	(10,000)		(10,000)		(7,778)
Intangibles, net	$ 0		$ 0		$ 2,222