Commitments, Contingencies and Credit Risk - Financial Instruments Whose Contractual Amounts Represent Credit Risk (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	$ 140,396	$ 96,117
Commitments to Grant Mortgage Loans
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	80,949	64,829
Commitments to Sell Loans at Lock-In Rates
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	16,537
Unfunded Commitments Under Lines of Credit
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	39,565	27,833
Standby Letters of Credit
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Contractual amounts represent credit risk	$ 3,345	$ 3,455