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Deferred Compensation And Retirement Plans (Components Of Net Periodic Benefit Costs) (Details) (USD $)
 3 Months Ended 9 Months Ended
Jan. 31, 2012
Jan. 31, 2011
Jan. 31, 2012
Jan. 31, 2011
Deferred Compensation And Retirement Plans [Abstract]        
Service cost   $ 34,000   $ 102,000
Interest cost 884,000 925,000 2,652,000 2,775,000
Amortization of actuarial loss 355,000 105,000 1,065,000 315,000
Net periodic benefit costs 1,239,000 1,064,000 3,717,000 3,192,000
Company contributions to the ECAP 200,000   15,500,000 400,000
Change in Fair Value of Vested Amounts owed under deferred compensation plan, (Income), Expense $ 1,600,000 $ 2,100,000 $ (2,000,000) $ 3,400,000
Deferred compensation arrangement vesting terms     Participants generally vest in Company contributions over a four year period.