Leases - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Finance lease cost:
Amortization of right-of-use assets	$ 5,564	$ 5,960	$ 11,156	$ 12,099
Interest on lease liabilities	2,123	2,863	4,424	5,925
Operating lease cost	11,314	10,630	22,327	21,329
Variable lease cost	4,629	3,157	8,552	6,132
Total lease cost	$ 23,630	$ 22,610	$ 46,459	$ 45,485