Deferred Compensation and Retirement Plans - Additional Information (Detail)	12 Months Ended
	Apr. 30, 2024 USD ($) participant jurisdiction	Apr. 30, 2023 USD ($) participant	Apr. 30, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Fair value of marketable securities increase (decrease)	$ 29,800,000	$ 2,900,000	$ (12,000,000)
Increase in market value of the underlying COLI investments	8,803,000	10,576,000	5,819,000
Net CSV	218,977,000	197,998,000
CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Total death benefits payable, net of loans	447,300,000	444,100,000
Increase in market value of the underlying COLI investments	8,800,000	10,600,000	5,800,000
Net CSV	$ 219,000,000	198,000,000
Minimum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range	40.00%
Minimum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range	40.00%
Maximum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range	60.00%
Maximum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation range	60.00%
Long Term Performance Unit Plan
Defined Benefit Plan Disclosure [Line Items]
Vesting percentage on each anniversary date	25.00%
Annual benefit payments per vested unit after anniversary period, option one	$ 10,000
Annual benefit payments per vested unit after anniversary period, option two	12,500
Annual benefit payments per vested unit after anniversary period, option three	$ 25,000
Number of payments after the seventh anniversary of the grant date	5 years
Long Term Performance Unit Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Value per unit award	$ 25,000
Long Term Performance Unit Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Value per unit award	$ 50,000
Enhanced Wealth Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Participant contribution period towards deferred compensation plans (in years)	8 years
Participant after tax contribution period towards deferred compensation plans (in years)	15 years
Additional deferred units to acquire (in years)	5 years
Medical And Life Insurance Benefits | Hay Group
Defined Benefit Plan Disclosure [Line Items]
Benefit plan, number of participants | participant	101
Total benefit obligation	$ 4,227,000	4,838,000	5,365,000
International retirement plans
Defined Benefit Plan Disclosure [Line Items]
Number of foreign jurisdictions | jurisdiction	25
Total benefit obligation	$ 12,600,000	$ 13,600,000
Long-term benefit obligation accrued, number of participants | participant	3,752	4,058
Company's contributions	$ 17,200,000	$ 16,400,000
Executive Capital Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	204,537,000	178,043,000	166,723,000
Company's contributions	$ 7,100,000	6,500,000	7,500,000
Deferred compensation arrangement vesting period	5 years
Deferred compensation plan expense (income)	$ 29,492,000	3,464,000	(10,600,000)
Company's contributions, unamortized portion	$ 16,400,000	16,100,000
Executive Capital Accumulation Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Option to receive employee benefits by quarterly installments periods	1 year
Executive Capital Accumulation Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Option to receive employee benefits by quarterly installments periods	15 years
Defined Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage contribution by the participants to defined contribution plan	50.00%
Employer matching contribution percentage	10.00%
Company's matching contributions	$ 3,500,000	3,500,000	2,100,000
Company's matching contributions next fiscal year	3,200,000
Company's additional matching contribution	3,100,000	2,700,000
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Total benefit obligation	280,926,000	246,340,000	$ 211,598,000
Deferred Compensation Plan | CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Gross CSV	295,900,000	275,100,000
Outstanding policy loans	77,000,000	$ 77,100,000
Company Owned Life Insurance Held In Trust | CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Net CSV	190,200,000
Total death benefits, net of loans held in trust	$ 392,500,000