Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 42,876	$ 42,150
Operating cash flows from finance leases	11,164	13,316
Financing cash flows from finance leases	30,371	25,275	$ 19,474
Right-of-use assets obtained in exchange for lease obligations
Operating leases	37,513	38,143
Finance leases	$ 27,400	$ 50,484