Deferred Compensation And Retirement Plans - Components of Net Periodic Benefits Costs (Detail) - Deferred Compensation Plan - USD ($) $ in Thousands		12 Months Ended
		Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 31,947	$ 24,939	$ 17,281
Interest cost		4,035	5,433	5,044
Amortization of actuarial loss		4,117	3,261	1,798
Net prior service credit amortization		(97)	(24)
Expected return on plan assets		(1,404)	(1,452)	(1,568)
Net periodic benefit cost	[1]	$ 38,598	$ 32,157	$ 22,555

[1] The service cost, interest cost and other components of net periodic benefit costs are included in compensation and benefits expense, interest expense, net and other income (loss), net, respectively, on the consolidated statements of income.