Retirement Plans (Schedule Of Fair Value Of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 65,746	$ 55,624	$ 60,536	$ 54,332
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65,586	55,487
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	160	137
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	160	137
Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	160	137
Vanguard Prime Money Market Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	160	137
Vanguard Prime Money Market Mutual Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	160	137
Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17,357	10,052
Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17,357	10,052
Vanguard Total Stock Market Index Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,374	5,513
Vanguard Total Stock Market Index Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,374	5,513
Vanguard Total International Stock Index Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,983	4,539
Vanguard Total International Stock Index Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,983	4,539
Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48,229	45,435
Fixed Income Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48,229	45,435
Vanguard Long-Term Investment Grade Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,694	27,260
Vanguard Long-Term Investment Grade Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,694	27,260
Vanguard Long-Term Bond Index Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,535	18,175
Vanguard Long-Term Bond Index Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 12,535	$ 18,175