Annual report pursuant to Section 13 and 15(d)

Deferred Compensation And Retirement Plans - Weighted-Average Assumptions Used In Calculating The Benefit Obligations (Detail)

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Deferred Compensation And Retirement Plans - Weighted-Average Assumptions Used In Calculating The Benefit Obligations (Detail)
12 Months Ended
Apr. 30, 2020
Apr. 30, 2019
Apr. 30, 2018
Pension Plans, Defined Benefit      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate, beginning of year 3.57% 3.93% 3.57%
Discount rate, end of year 2.29% 3.57% 3.93%
Rate of compensation increase 0.00% 0.00% 0.00%
Expected long-term rates of return on plan assets 6.00% 6.00% 6.25%
Medical and Life Insurance plan | Hay Group      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate, beginning of year 3.67% 3.94% 3.75%
Discount rate, end of year 2.45% 3.67% 3.94%
Healthcare care cost trend rate 6.50% 6.50% 7.00%