Borrowings - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Advance from the Federal Home Loan Bank	$ 117,283		$ 117,283		$ 104,404
Guarantee from the FHLBNY through a standby letter of credit	3,345		3,345		3,455
Unsecured fed fund line amount outstanding	25,000		25,000		25,000
Unsecured fed fund line amount outstanding	5,835		5,835
Interest expense on FHLBNY advances	612	$ 516	1,799	$ 1,141
Interest Expense on overnight advances	43	$ 17	51	$ 70
Collateral in residential 1-4 and multifamily mortgage loans available to secure advances from the FHLBNY	329,743		329,743		301,753
Mortgage loans funding payable	1,457		1,457
Warehouse Line of Credit #1
Line Of Credit Facility [Line Items]
Unsecured fed fund line amount outstanding	$ 2,221		$ 2,221
Debt Instrument, Interest Rate, Basis for Effective Rate			The interest rate is based on the 30-day LIBOR rate plus 3.25%.
Line of credit facility, effective interest rate	3.40%		3.40%
Warehouse Line of Credit #2
Line Of Credit Facility [Line Items]
Unsecured fed fund line amount outstanding	$ 3,614		$ 3,614
Debt Instrument, Interest Rate, Basis for Effective Rate			The interest rate is based on the 30-day LIBOR rate plus 3.00%
Line of Credit Facility, Interest Rate	3.15%		3.15%
Variable Rate Above LIBOR | Warehouse Line of Credit #1
Line Of Credit Facility [Line Items]
Interest rate, LIBOR/Variable rate			3.25%
Variable Rate Above LIBOR | Warehouse Line of Credit #2
Line Of Credit Facility [Line Items]
Interest rate, LIBOR/Variable rate			3.00%
FHLBNY
Line Of Credit Facility [Line Items]
Unsecured fed fund line amount outstanding	$ 0		$ 0		$ 0