Deferred Compensation and Retirement Plans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Apr. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Increase in market value of the underlying COLI investments	$ 2,105	$ 2,338
Recognized investment income (expense)	$ 11,500	1,900
Executive Capital Accumulation Plan
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation arrangement vesting period	5 years
Gain (loss) on deferred compensation plan	$ 11,200	2,300
Minimum
Defined Benefit Plan Disclosure [Line Items]
Option to receive employee benefits by quarterly installments periods	1 year
Maximum
Defined Benefit Plan Disclosure [Line Items]
Option to receive employee benefits by quarterly installments periods	15 years
CSV of COLI Contracts
Defined Benefit Plan Disclosure [Line Items]
Gross CSV	$ 240,100		$ 238,700
Outstanding policy loans	91,700		$ 92,300
Increase in market value of the underlying COLI investments	$ 2,100	$ 2,300