Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 30,976
Operating cash flows from finance leases	10,089
Financing cash flows from finance leases	17,971	$ 13,923
Right-of-use assets obtained in exchange for lease obligations - Operating leases	32,042
Right-of-use assets obtained in exchange for lease obligations - Finance leases	$ 39,379