Fair Value - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value (Note 4)	$ 14,512	$ 21,504
Warehouse lines of credit (Note 8)	9,065
Mortgage loan fundings payable (Note 8)	1,457
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	76,092	27,677
Available-for-sale securities, at fair value (Note 4)	14,512	21,504
Placements with banks	2,739
Mortgage loans held for sale, at fair value	13,100	1,030
Loans receivable, net	1,108,956	955,737
Accrued interest receivable	9,995	3,982
FHLBNY stock	6,414	5,735
Other assets	58
Demand deposits	186,328	109,548
Interest-bearing deposits	407,745	282,997
Certificates of deposit	379,171	389,498
Advance payments by borrowers for taxes and insurance	7,739	6,348
Advances from FHLBNY	117,283	104,404
Warehouse lines of credit (Note 8)	9,065
Mortgage loan fundings payable (Note 8)	1,457
Available-for-Sale Securities After one year through five years, Amortized Cost	58	97
Fair Value Measurements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	76,092	27,677
Available-for-sale securities, at fair value (Note 4)	14,512	21,504
Placements with banks	2,739
Mortgage loans held for sale, at fair value	13,100	1,030
Loans receivable, net	1,124,149	959,942
Accrued interest receivable	9,995	3,982
FHLBNY stock	6,414	5,735
Other assets	58
Demand deposits	186,328	109,548
Interest-bearing deposits	407,745	282,997
Certificates of deposit	384,884	393,254
Advance payments by borrowers for taxes and insurance	7,739	6,348
Advances from FHLBNY	117,283	104,404
Warehouse lines of credit (Note 8)	9,065
Mortgage loan fundings payable (Note 8)	1,457
Available-for-Sale Securities After one year through five years, Amortized Cost	58	97
Fair Value Measurements \| Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	76,092	27,677
FHLBNY stock	6,414	5,735
Demand deposits	186,328	109,548
Interest-bearing deposits	407,745	282,997
Advances from FHLBNY	117,283	104,404
Warehouse lines of credit (Note 8)	9,065
Mortgage loan fundings payable (Note 8)	1,457
Fair Value Measurements \| Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale securities, at fair value (Note 4)	14,512	21,504
Placements with banks	2,739
Mortgage loans held for sale, at fair value	13,100	1,030
Accrued interest receivable	9,995	3,982
Certificates of deposit	384,884	393,254
Advance payments by borrowers for taxes and insurance	7,739	6,348
Available-for-Sale Securities After one year through five years, Amortized Cost		97
Fair Value Measurements \| Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans receivable, net	1,124,149	$ 959,942
Other assets	58
Available-for-Sale Securities After one year through five years, Amortized Cost	$ 58

Accrued interest payable fair value.

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Accrued interest receivable fair value.

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Advance payments by borrowers for taxes and insurance fair value.

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Certificates of deposit fair value.

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Demand deposit liability fair value.

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Interest bearing deposit fair value.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Fair value portion of mortgage loans held-for-sale.

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Fair value portion of other assets.

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The aggregate amount of the participation liability at the end of the accounting period.

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Carrying value as of the balance sheet date of the outstanding short-term borrowings under a revolving line of credit used by mortgage bankers to finance the origination or purchase of loans.

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