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Defined Pension Plans (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]        
Pension period     30 years  
Defined Benefit Pension Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Pension costs $ 1,033 $ 965 $ 3,070 $ 2,724
Unfunded Supplemental Executive Retirement Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Pension costs $ 210 $ 201 $ 628 $ 604