Borrowed Funds (Details) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($) item $ / item	Dec. 31, 2020 USD ($)
Advances from Federal Home Loan Banks and Letters of Credit	$ 1,429,600
Subordinated Borrowing, Interest Rate	3.125%
Subordinated debentures	$ 122,885	$ 90,180
Repayments of subordinated debt	$ 90,300
Number of repayments for subordinated debt in call feature \| item	3
Subordinated debt called at par \| item	2
Capital Securities [Member] \| Flushing Financial Capital Trust IV [Member]
Proceeds from Issuance of Debt	$ 20,600
Capital Securities [Member] \| Flushing Financial Capital Trust II [Member]
Proceeds from Issuance of Debt	20,600
Capital Securities [Member] \| Flushing Financial Capital Trust III [Member]
Proceeds from Issuance of Debt	20,600
Unsecured Line of Credit [Member]
Unsecured lines of credit	593,000
Federal Home Loan Bank of New York [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	3,635,200
Federal Home Loan Bank advances and other borrowings	$ 611,187	797,201
Federal Home Loan Bank Advances [Member] \| Federal Home Loan Bank of New York [Member] \| Minimum [Member]
Debt Instrument, Term	1 day
Federal Home Loan Bank Advances [Member] \| Federal Home Loan Bank of New York [Member] \| Maximum [Member]
Debt Instrument, Term	5 years
Other Borrowings [Member] \| Other Borrowings Due in 2022
Unsecured debt	$ 25,000	90,378
Subordinated Debentures
Net Proceeds	122,800
Debt Instrument, Face Amount	125,000
Subordinated debentures	122,885	90,180
Unamortized debt issuance costs	2,100
Subordinated Debentures \| Subordinated debentures Due in 2025
Subordinated debentures	0	15,523
Subordinated Debentures \| Subordinated debentures Due in 2026
Subordinated debentures	0	$ 74,657
Subordinated Debentures \| Subordinated debentures Due in 2031
Subordinated debentures	122,885
Subordinated Debt One [Member]
Repayments of subordinated debt	75,000
Subordinated Debt Two [Member]
Repayments of subordinated debt	7,800
Subordinated Debt Three [Member]
Repayments of subordinated debt	$ 7,500
Subordinated debt, premium \| $ / item	102.5
Premium paid upon call	$ 200

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

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The amount of premium on repayment of subordinated debt in call feature.

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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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Face (par) amount of debt instrument at time of issuance.

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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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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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Stated interest rate of the subordinated debt.

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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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