Retirement Plans (Summary Of The Fair Values Of Pension Plan Investments According To The Fair Value Hierarchy And The Weighted Average Allocations) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	$ 11,082	$ 9,484
Guaranteed Deposit Account [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	11,082	9,484	$ 11,515
Guaranteed Deposit Account [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	11,082	9,484
Limited Liability Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	5,100	6,200
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	10,170	6,482
Common Stock [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	10,170	6,482
Common Stock [Member] | Insurance Company Pooled Separate Accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	91,900	88,400
Debt Investments [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	5,810	5,250
Debt Investments [Member] | Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	5,810	5,250
Debt Investments [Member] | Insurance Company Pooled Separate Accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	28,800	31,700
Real Estate [Member] | Insurance Company Pooled Separate Accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan investments	$ 8,100	$ 9,900