Annual report pursuant to Section 13 and 15(d)

Retirement Plans and Related Post Retirement Benefits - Summarizes the Components of the Net Periodic Cost (Details)

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Retirement Plans and Related Post Retirement Benefits - Summarizes the Components of the Net Periodic Cost (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
SERP      
Net Periodic Cost      
Service Cost — Benefits Earned During Period $ 181 $ 200 $ 186
Interest Cost 916 899 897
Amortization of Prior Service Cost 386 386 387
Amortization of Losses 300 629 369
Net Periodic Cost 1,783 2,114 1,839
SERP Medical      
Net Periodic Cost      
Service Cost — Benefits Earned During Period 13 16 7
Interest Cost 46 46 41
Amortization of Prior Service Cost 16 16 16
Amortization of Losses 43 59 31
Net Periodic Cost $ 118 $ 137 $ 95