Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 42,150
Operating cash flows from finance leases	13,316
Financing cash flows from finance leases	25,275	$ 19,474	$ 6,132
Right-of-use assets obtained in exchange for lease obligations - Operating leases	38,143
Right-of-use assets obtained in exchange for lease obligations - Finance leases	$ 50,484