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Employee Benefit Plans And Other Postretirement Benefits (Components Of Net Postretirement Costs) (Details) (Net Postretirement Costs [Member], USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Net Postretirement Costs [Member]
    
Defined Benefit Plan Disclosure [Line Items]    
Service cost for benefits earned during the year $ 464 $ 400
Interest cost on accumulated benefit obligation 310 297
Net amortization of unrecognized amounts, Prior service cost (104) (104)
Net amortization of unrecognized amounts, Actuarial loss 113 112
Net periodic benefit cost $ 783 $ 705