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)
Apr. 30, 2013
Apr. 30, 2012
Apr. 30, 2011
Apr. 30, 2010
Deferred Compensation Plan
       
Defined Benefit Plan Disclosure [Line Items]        
Discount rate, beginning of year 3.12% 3.79% 4.94% 5.61%
Discount rate, end of year 3.12% 3.79% 4.94% 5.61%
Rate of compensation increase 0.00% 0.00% 0.00%  
Pension Plans, Defined Benefit
       
Defined Benefit Plan Disclosure [Line Items]        
Discount rate, beginning of year 3.12% 3.79% 4.94% 5.61%
Discount rate, end of year 3.12% 3.79% 4.94% 5.61%
Rate of compensation increase 0.00% 0.00% 0.00%