Deferred Compensation and Retirement Plans - Components of Net Periodic Benefits Costs (Detail) - Deferred Compensation Plan - USD ($) $ in Thousands		3 Months Ended
		Jul. 31, 2019	Jul. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 5,456	$ 3,646
Interest cost		1,393	1,296
Amortization of actuarial loss		745	446
Expected return on plan assets	[1]	(363)	(392)
Net periodic service credit amortization		(77)	(77)
Net periodic benefit costs	[2]	$ 7,154	$ 4,919

[1] The expected long-term rate of return on plan assets was 6.00% and 6.25% for July 31, 2019 and 2018, respectively.

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