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Self-Insurance Reserves - Additional Information (Detail) - USD ($)
Apr. 30, 2021
Apr. 30, 2020
Apr. 30, 2019
Commitments And Contingencies Disclosure [Abstract]      
Reserves for workers' compensation, product liability, municipal liability, and medical/dental costs $ 9,469,000 $ 9,011,000 $ 8,423,000
Reserves for workers' compensation, product liability, municipal liability, and medical/dental costs, Non-current portion 5,000,000.0 4,500,000  
Reserves for workers' compensation, product liability, municipal liability, and medical/dental costs, included in accrued expenses 4,500,000 4,500,000  
Workers' compensation receivable classified as an other assets 614,000 620,000  
Accrued reserves for product and municipal litigation liabilities 4,000,000.0 3,700,000  
Accrued reserves for product and municipal litigation liabilities, Non-current portion 2,900,000 2,600,000  
Receivables from insurance carriers, included in other assets $ 0 $ 1,900,000