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Postretirement Benefit Plans (Net Periodic Benefit (Income) Costs) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Postretirement Health And Life Coverage [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 3 $ 4 $ 4
Interest cost 17 17 20
Amortization of prior service cost (25) (25) (35)
Amortization of net (gain) or loss (5) (1)  
Net periodic postretirement benefit (income) cost (10) (5) (11)
Director's Retirement Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 51 36 35
Interest cost 42 38 43
Amortization of prior service cost   22 22
Net periodic postretirement benefit (income) cost 93 96 $ 100
Defined Benefit Pension Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 92 287  
Interest cost 217 392  
Expected return on plan assets (254) (423)  
Recognized net actuarial (gain) loss (59)    
Net periodic postretirement benefit (income) cost $ (4) $ 256