Commitments and Contingencies - Summary of outstanding loan commitments, unused lines of credit and letters of credit (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	$ 29,332	$ 23,482
Other Mortgage Loans
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	2,229	2,816
Line Of Credit Home Equity
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	8,672	7,825
Line Of Credit Commercial
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	19,982	15,003
Line Of Credit Consumer Unsecured
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	678	654
Letter Of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	$ 1,044	$ 1,059