Fair Value - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value	$ 116,753	$ 129,505
Held-to-maturity securities, at amortized cost, net		510,820
Loans held for sale, at fair value	14,103	1,979
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	117,012	54,360
Available-for-sale securities, at fair value	116,753	129,505
Held-to-maturity securities, at amortized cost, net	471,065	510,820
Placements with banks	996	1,494
Loans held for sale, at fair value	14,103	1,979
Loans receivable, net	1,787,607	1,493,127
Accrued interest receivable	16,624	15,049
FHLBNY stock	18,870	24,661
Demand deposits	265,862	289,149
Interest-bearing deposits	593,559	504,973
Certificates of deposit	541,711	458,290
Advance payments by borrowers for taxes and insurance	13,743	9,724
Borrowings	675,100	517,375
Accrued interest payable	8,385	1,390
Fair Value Measurements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	117,012	54,360
Available-for-sale securities, at fair value	116,753	129,505
Held-to-maturity securities, at amortized cost, net	444,864	495,851
Placements with banks	996	1,494
Loans held for sale, at fair value	14,103	1,979
Loans receivable, net	1,720,035	1,430,864
Accrued interest receivable	16,624	15,049
FHLBNY stock	18,870	24,661
Demand deposits	265,862	289,149
Interest-bearing deposits	593,559	504,973
Certificates of deposit	529,450	450,224
Advance payments by borrowers for taxes and insurance	13,743	9,724
Borrowings	654,847	503,406
Accrued interest payable	8,385	1,390
Fair Value Measurements | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	117,012	54,360
Available-for-sale securities, at fair value	3,442	3,419
FHLBNY stock	18,870	24,661
Demand deposits	265,862	289,149
Interest-bearing deposits	593,559	504,973
Fair Value Measurements | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value	113,311	126,086
Held-to-maturity securities, at amortized cost, net	444,864	495,851
Placements with banks	996	1,494
Loans held for sale, at fair value	14,103	1,979
Accrued interest receivable	16,624	15,049
Certificates of deposit	529,450	450,224
Advance payments by borrowers for taxes and insurance	13,743	9,724
Borrowings	654,847	503,406
Accrued interest payable	8,385	1,390
Fair Value Measurements | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	$ 1,720,035	$ 1,430,864