Leases - Future minimum lease payments under non-cancellable leases (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Finance lease
2022	$ 44,209
2023	35,538
2024	26,259
2025	15,266
2026	7,627
Thereafter	3,051
Total lease payments	131,950
Less imputed interest	14,002
Finance lease obligations	117,948	$ 128,767
Operating lease
2022	39,474
2023	32,704
2024	26,764
2025	18,455
2026	8,707
Thereafter	15,197
Total lease payments	141,301
Less imputed interest	17,537
Total	$ 123,764