Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 10,141
Operating cash flows from finance leases	6,789
Financing cash flows from finance leases	12,310	$ 8,820
Right-of-use assets obtained in exchange for lease obligations - Operating leases	6,569
Right-of-use assets obtained in exchange for lease obligations - Finance leases	$ 22,812