Commitments and Contingencies - Summary of outstanding loan commitments, unused lines of credit and letters of credit (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	$ 23,482	$ 19,905
Other Mortgage Loans
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	2,816	3,589
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	7,825	9,118
Line Of Credit Commercial
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	15,003	10,061
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	654	726
Letter Of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	$ 1,059	$ 1,059