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Pension and Postretirement Benefit Plans (Net Periodic Benefit Cost of the Pension Plan and Postretirement Benefit Plan) (Details) - Postretirement Benefits Plan [Member] - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 0 $ 0 $ 0
Interest cost 3 4 4
Expected return on plan assets 0 0 0
Amortization of prior service costs 0 0 0
Amortization of transition obligation 0 0 0
Recognized net loss due to settlement 0 0 0
Amortization of net actuarial gain (7) (6) (6)
Net periodic benefit cost $ (4) $ (2) $ (2)