Segments - Fee Revenue Classified by Country (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Segment Reporting Information [Line Items]
Total revenue	$ 2,863,836	$ 2,643,455	$ 1,819,946
Fee revenue
Segment Reporting Information [Line Items]
Total revenue	2,835,408	2,626,718	1,810,047
Fee revenue | U.S.
Segment Reporting Information [Line Items]
Total revenue	1,568,119	1,348,377	837,682
Fee revenue | United Kingdom
Segment Reporting Information [Line Items]
Total revenue	255,797	247,617	189,893
Fee revenue | Other countries
Segment Reporting Information [Line Items]
Total revenue	$ 1,011,492	$ 1,030,724	$ 782,472