Borrowed Funds (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Collateral pledged real estate loans	$ 5,400,000
Advances from Federal Home Loan Banks and Letters of Credit	1,599,500
Subordinated debentures	187,630	$ 186,965
Capital Securities \| Flushing Financial Capital Trust IV
Proceeds from Issuance of Debt	20,600
Capital Securities \| Flushing Financial Capital Trust II
Proceeds from Issuance of Debt	20,600
Capital Securities \| Flushing Financial Capital Trust III
Proceeds from Issuance of Debt	20,600
Unsecured Line of Credit
Unsecured lines of credit	1,103,000
Long-term Line of Credit, Total	25,000
FHLB-NY
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	3,808,600
Federal Home Loan Bank advances and other borrowings	480,801	815,501
Federal Reserve
Secured borrowing	$ 100,000
FHLB \| FHLB-NY \| Minimum
Debt Instrument, Term	7 days
FHLB \| FHLB-NY \| Maximum
Debt Instrument, Term	5 years
Other Borrowings \| Other Borrowings Due in 2024
Unsecured debt	$ 125,000
Subordinated debentures
Subordinated debentures	187,630	$ 186,965
Unamortized debt issuance costs	$ 2,400

The amount outstanding of advances from FHLB and Letters of Credit.

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The amount pledged real estate loans as collateral.

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount of maximum advances or credit lines available from the Federal Home Loan Bank (FHLB).

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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