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Deferred Compensation and Retirement Plans - Additional Information (Detail) | 12 Months Ended
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Apr. 30, 2021 USD ($) Person Jurisdiction | Apr. 30, 2020 USD ($) Person | Apr. 30, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |
Recognized investment income(expense) | $ 38,500,000 | $ (1,800,000) | $ 8,100,000
Increase in market value of the underlying COLI investments | 13,017,000 | 6,551,000 | 6,160,000
Net CSV | 161,295,000 | 146,408,000 |
CSV of COLI Contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Outstanding policy loans | 80,000,000.0 | 92,300,000 |
Total death benefits payable, net of loans | 443,900,000 | 451,700,000 |
Increase in market value of the underlying COLI investments | 13,000,000.0 | 6,600,000 | 6,200,000
Net CSV | $ 161,300,000 | 146,400,000 |
Equity Securities | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target allocation range | 50.00% |  |
Equity Securities | Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target allocation range | 70.00% |  |
Debt Securities | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target allocation range | 30.00% |  |
Debt Securities | Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target allocation range | 50.00% |  |
Long Term Performance Unit Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Value per unit award | $ 50,000 |  |
Annual Benefit Payments per vested unit after anniversary period | $ 25,000 |  |
Number of payments after the seventh anniversary of the grant date | 5 years |  |
Vesting percentage on each anniversary date | 25.00% |  |
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 plan | Hay Group |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Benefit plan, number of participants | Person | 118 |  |
Total benefit obligation | $ 6,584,000 | 7,527,000 | 7,310,000
International Retirement Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Number of foreign jurisdictions | Jurisdiction | 24 |  |
Total benefit obligation | $ 15,600,000 | $ 14,900,000 |
Long-term benefit obligation accrued, number of participants | Person | 2,557 | 2,991 |
Company's contributions | $ 12,700,000 | $ 14,400,000 |
Executive Capital Accumulation Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total benefit obligation | 163,582,000 | 129,315,000 | 130,161,000
Company's contributions | $ 8,200,000 | 9,000,000.0 | 8,500,000
Deferred compensation arrangement vesting period | 5 years |  |
Gain (loss) on deferred compensation plan | $ 37,300,000 | (800,000) | 8,700,000
Company's contributions, unamortized portion | $ 20,200,000 | 17,000,000.0 |
Defined Contribution Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Company's matching contributions |  | 3,000,000.0 |
Percentage contribution by the participants to defined contribution plan | 50.00% |  |
Deferred Compensation Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total benefit obligation | $ 205,740,000 | 180,821,000 | $ 148,369,000
Deferred Compensation Plan | CSV of COLI Contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Gross CSV | 241,300,000 | 238,700,000 |
Outstanding policy loans | 80,000,000.0 | $ 92,300,000 |
Company Owned Life Insurance Held In Trust | CSV of COLI Contracts |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Net CSV | 145,100,000 |  |
Total death benefits, net of loans held in trust | $ 398,900,000 |  |

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