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Income Taxes (Details) - USD ($)
 3 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes        
Federal corporate income tax rate (as a percent)   18.21% 19.18% 13.47%
Income tax benefit attributable to Tax Act $ 343,000      
Income tax benefit related additional tax planning initiatives 143,000      
Income tax benefit attributable to the pension contribution 306,000      
Income tax benefit attributable to accounting method changes on tax return $ 180,000