Borrowings - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Line Of Credit Facility [Line Items]
Federal Home Loan Bank (FHLB) advances	$ 49,020,000	$ 19,117,000
Fair value adjustment		1,100,000
Advances from FHLB collateralized by certain loans	328,600,000	309,900,000
Investment in FHLB stock	2,200,000	1,300,000
FHLB advances book value		1,800,000
Line of credit amount outstanding	8,000,000.0	16,000,000.0
Paycheck protection program liquidity facility (PPPLF) borrowings		100,813,000
Small Business Administration
Line Of Credit Facility [Line Items]
Secured payroll protection program loans	0	101,700,000
Federal Reserve Bank of Atlanta | Small Business Administration
Line Of Credit Facility [Line Items]
Paycheck protection program liquidity facility (PPPLF) borrowings		$ 100,800,000
Payroll protection program loans, fixed interest rate		0.35%
Federal Reserve Bank of Atlanta | Small Business Administration | Minimum
Line Of Credit Facility [Line Items]
Payroll protection program loans, maturity period		2 years
Federal Reserve Bank of Atlanta | Small Business Administration | Maximum
Line Of Credit Facility [Line Items]
Payroll protection program loans, maturity period		5 years
Revolving Credit Facility | First National Bankers Bank
Line Of Credit Facility [Line Items]
Line of credit amount outstanding	$ 0	$ 5,000,000.0
Line of credit, term	10 years
Line of credit, frequency of payment and payment terms	Interest payment were due quarterly and the initial principal payment was due June 29, 2021.
Line of credit, initial principal payment due date	Jun. 29, 2021
Line of credit, prepayment penalty	$ 0