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Pension And Postretirement Benefit Plans (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
employee
Jun. 30, 2017
USD ($)
Defined Benefit Plan Disclosure [Line Items]        
Retired employees receiving health care and life insurance benefits | employee     9  
Post retirement benefits, age eligibility requirement     65 years  
Post retirement benefits, service eligibility requirement     15 years  
Postretirement Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Net periodic benefit cost | $ $ (1) $ (1) $ (2) $ (2)