Annual report pursuant to Section 13 and 15(d)

Deferred Compensation And Retirement Plans (Reconciliation Of Benefit Obligation) (Parenthetical) (Detail)

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Deferred Compensation And Retirement Plans (Reconciliation Of Benefit Obligation) (Parenthetical) (Detail) - CSV of COLI Contracts - USD ($)
$ in Millions
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2015
Defined Benefit Plan Disclosure [Line Items]      
Gross CSV $ 180.3 $ 175.7  
Outstanding policy loans 67.2 68.4  
Deferred Compensation Plan      
Defined Benefit Plan Disclosure [Line Items]      
Gross CSV 180.3 175.7 $ 172.3
Outstanding policy loans $ 67.2 $ 68.4 $ 69.6