Fair Value - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value	$ 111,005	$ 119,902
Held-to-maturity securities, at amortized cost, net		461,748
Mortgage loans held for sale, at fair value	9,566	9,980
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	155,812	139,190
Available-for-sale securities, at fair value	111,005	119,902
Held-to-maturity securities, at amortized cost, net	403,736	461,748
Placements with banks	249	249
Mortgage loans held for sale, at fair value	9,566	9,980
Loans receivable, net	2,180,331	1,895,886
Accrued interest receivable	16,890	18,010
FHLBNY stock	28,515	19,377
Interest rate swap	4,352	4,435
Demand deposits	182,737	185,151	[1]
Interest-bearing deposits	934,699	721,643	[1]
Certificates of deposit	752,887	600,826
Advance payments by borrowers for taxes and insurance	13,733	10,778
Borrowings	580,421	684,421
Accrued interest payable	2,918	11,965
Interest rate swap	$ 4,352	$ 4,435
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Financing Receivable, after Allowance for Credit Loss	Financing Receivable, after Allowance for Credit Loss
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other Liabilities	Other Liabilities
Fair Value Measurements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 155,812	$ 139,190
Available-for-sale securities, at fair value	111,005	119,902
Held-to-maturity securities, at amortized cost, net	398,823	450,042
Placements with banks	249	249
Mortgage loans held for sale, at fair value	9,566	9,980
Loans receivable, net	2,153,077	1,844,507
Accrued interest receivable	16,890	18,010
FHLBNY stock	28,515	19,377
Interest rate swap	4,352	4,435
Demand deposits	182,737	185,151	[1]
Interest-bearing deposits	934,699	721,643	[1]
Certificates of deposit	751,665	594,234
Advance payments by borrowers for taxes and insurance	13,733	10,778
Borrowings	577,809	674,155
Accrued interest payable	2,918	11,965
Interest rate swap	4,352	4,435
Fair Value Measurements | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	155,812	139,190
Available-for-sale securities, at fair value	2,869	3,320
FHLBNY stock	28,515	19,377
Demand deposits	182,737	185,151	[1]
Interest-bearing deposits	934,699	721,643	[1]
Fair Value Measurements | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value	108,136	116,582
Held-to-maturity securities, at amortized cost, net	398,823	450,042
Placements with banks	249	249
Mortgage loans held for sale, at fair value	9,566	9,980
Accrued interest receivable	16,890	18,010
Interest rate swap	4,352	4,435
Certificates of deposit	751,665	594,234
Advance payments by borrowers for taxes and insurance	13,733	10,778
Borrowings	577,809	674,155
Accrued interest payable	2,918	11,965
Interest rate swap	4,352	4,435
Fair Value Measurements | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	$ 2,153,077	$ 1,844,507

[1] As of December 31, 2023, $58.2 million were reclassified from demand deposits to interest-bearing deposits.