Leases - Components of lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Finance lease cost:
Amortization of right-of-use assets	$ 23,769	$ 24,352
Interest on lease liabilities	11,164	13,316
Operating lease cost	42,383	42,846
Variable lease cost	12,914	12,555
Total lease cost	$ 90,230	$ 93,069
Rent expense			$ 53,500