Transactions With Related Parties - Facilities Rental (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Transactions with related parties
Aggregate future minimum payments due	$ 140,779
Affiliated partnerships or entities | Lease of warehouse facilities
Transactions with related parties
Aggregate future minimum payments due	1,200
Affiliated partnerships or entities | Lease of warehouse facilities | Selling, general and administrative expenses
Transactions with related parties
Rent expense	$ 800	$ 800	$ 800