Allowance for Credit Losses (Non-accrual Basis By Loan Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 3,761	$ 4,886
Commercial, financial and agricultural | Domestic | Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	1,444	1,901
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	501	1,208
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	137	165
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	911	938
Real estate - mortgage | Domestic | Residential First Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	727	670
Real estate - mortgage | Domestic | Residential Junior Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	38
Consumer | Domestic
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 3	$ 4