Deferred Compensation and Retirement Plans - Reconciliation of Deferred Compensation and Pension Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Change in fair value of plan assets:
Total liability	$ 423,753	$ 376,091
Deferred Compensation Plan
Change in benefit obligation:
Balance, beginning of year	211,598	205,740
Service cost	40,843	37,952	$ 31,947
Interest cost	9,511	4,028	4,035
Actuarial gain	(6,083)	(25,757)
Administrative expenses paid	(168)	(196)
Benefits paid from plan assets	(1,901)	(2,543)
Benefits paid from cash	(7,460)	(7,626)
Balance, end of year	246,340	211,598	205,740
Change in fair value of plan assets:
Fair value of plan assets, beginning of year	21,990	26,746
Actual return on plan assets	(836)	(2,113)
Benefits paid from plan assets	(1,901)	(2,543)
Administrative expenses paid	(168)	(196)
Employer contributions	0	96
Fair value of plan assets, end of year	19,085	21,990	$ 26,746
Funded status and balance, end of year	(227,255)	(189,608)
Current liability	15,447	8,833
Non-current portion	211,808	180,775
Total liability	$ 227,255	$ 189,608
Plan assets weighted average allocation	100.00%	100.00%
Deferred Compensation Plan | CSV of COLI Contracts
Change in fair value of plan assets:
Gross CSV	$ 275,100	$ 263,200
Outstanding policy loans	$ 77,100	$ 79,800
Deferred Compensation Plan | Debt securities
Change in fair value of plan assets:
Plan assets weighted average allocation	44.00%	42.00%
Deferred Compensation Plan | Equity securities
Change in fair value of plan assets:
Plan assets weighted average allocation	52.00%	55.00%
Deferred Compensation Plan | Other
Change in fair value of plan assets:
Plan assets weighted average allocation	4.00%	3.00%