Segments - Fee Revenue Classified by Country (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 2,643,455	$ 1,819,946	$ 1,977,330
Fee Revenue
Segment Reporting Information [Line Items]
Total revenue	2,626,718	1,810,047	1,932,732
Fee Revenue | UNITED STATES
Segment Reporting Information [Line Items]
Total revenue	1,348,377	837,682	875,605
Fee Revenue | United Kingdom
Segment Reporting Information [Line Items]
Total revenue	247,617	189,893	204,271
Fee Revenue | Other Countries
Segment Reporting Information [Line Items]
Total revenue	$ 1,030,724	$ 782,472	$ 852,856