Retirement Plans (Summary Of Reconciliation Of The Beginning And Ending Balances Of Assets Measured At Fair Value On A Recurring Basis Using Level 3 Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Administration Expenses	$ (481)	$ (376)
Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	9,484
Fair value of plan assets at end of year	11,082	9,484
Defined benefit plan investment purchases	14,974	10,428
Purchases	(12,976)	(11,739)
Unrealized Appreciation (Depreciation) In Fair Value Of Investments [Member] | Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Net increases (decreases) included in plan statement of changes in net assets available for benefits	(151)	(628)
Interest And Dividends [Member] | Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Net increases (decreases) included in plan statement of changes in net assets available for benefits	232	284
Fair Value, Inputs, Level 2 [Member] | Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	9,484	11,515
Fair value of plan assets at end of year	11,082	9,484
Fair Value, Inputs, Level 3 [Member] | Guaranteed Deposit Account [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	9,484
Fair value of plan assets at end of year	$ 11,082	$ 9,484