Deferred Compensation And Retirement Plans - Reconciliation Of Benefit Obligation (Detail) - USD ($) $ in Thousands		12 Months Ended
		Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation		$ 364,793	$ 308,279
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, beginning of year		180,821	148,369
Service cost		31,947	24,939	$ 17,281
Interest cost		4,035	5,433	5,044
Actuarial (gain) loss		(590)	13,427
Administrative expenses paid		(265)	(155)
Benefits paid from plan assets		(2,327)	(3,932)
Benefits paid from cash		(7,881)	(6,652)
Plan amendment			(608)
Benefit obligation, end of year		205,740	180,821	148,369
Fair value of plan assets, beginning of year		24,235	25,131
Actual return on plan assets		4,523	2,726
Benefits paid from plan assets		(2,327)	(3,932)
Administrative expenses paid		(265)	(155)
Employer contributions		580	465
Fair value of plan assets, end of year		26,746	24,235	25,131
Funded status and balance, end of year	[1]	(178,994)	(156,586)
Current liability		9,074	8,887
Non-current liability		169,920	147,699
Total benefit obligation		$ 178,994	$ 156,586
Plan assets weighted average allocation		100.00%	100.00%
Deferred Compensation Plan | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets weighted average allocation		36.00%	43.00%
Deferred Compensation Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets weighted average allocation		62.00%	56.00%
Deferred Compensation Plan | Other securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets weighted average allocation		2.00%	1.00%
Executive Capital Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation, beginning of year		$ 129,315	$ 130,161
Employee contributions		4,935	8,215
Amortization of employer contributions		6,287	6,074
Gain on investment		37,323	(826)
Benefits paid from cash		(15,652)	(13,911)
Exchange rate fluctuations		1,374	(398)
Benefit obligation, end of year		163,582	129,315	$ 130,161
Current liability		8,663	9,590
Non-current liability		154,919	119,725
Total benefit obligation		$ 163,582	$ 129,315

[1] The Company purchased COLI contracts insuring the lives of certain employees eligible to participate in the deferred compensation and pension plans as a means of funding benefits under such plans. As the COLI contracts are held in trust and are not separated from our general corporate assets, they are not included in the funded status. As of April 30, 2021 and 2020, the Company held contracts with gross CSV of $241.3 million and $238.7 million, offset by outstanding policy loans of $80.0 million and $92.3 million, respectively