Maximum length of time until the line of credit matures.

No definition available.

Name:	ffic_LineOfCreditMaturityMax
Namespace Prefix:	ffic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loan commitments expiration period.

+ References

No definition available.

+ Details

Name:	ffic_LoanCommitmentsExpiration
Namespace Prefix:	ffic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the amount of cash required to fully fund agreements to provide credit to borrowers.

+ References

No definition available.

+ Details

Name:	ffic_LoansAndLeasesReceivableCommitmentsCredit
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Reflects the weighted average interest rate on commitments to advance to borrowers and lessees at interest rates that increase or decrease depending on certain facts or circumstances.

+ References

No definition available.

+ Details

Name:	ffic_LoansAndLeasesReceivableCommitmentsVariableRatesWeightedAverageRate
Namespace Prefix:	ffic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the weighted average interest rate associated with agreements to provide advances to borrowers and lessees at stated interest rates.

+ References

No definition available.

+ Details

Name:	ffic_LoansAndLeasesReceivableCommitmentsWeightedAverageRateOfInterest
Namespace Prefix:	ffic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of securities, mortgage loans, or other financial instruments pledged as collateral for deposits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818

+ Details

Name:	us-gaap_DepositLiabilitiesCollateralIssuedFinancialInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the amount of cash required to fully fund agreements to provide advances to borrowers and lessees at stated interest rates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=108315417&loc=d3e61044-112788

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=108315417&loc=d3e61082-112788

+ Details

Name:	us-gaap_LoansAndLeasesReceivableCommitmentsFixedRates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reflects the amount of cash required to fully fund agreements to provide advances to borrowers and lessees at interest rates that increase or decrease depending on certain facts or circumstances.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=108315417&loc=d3e61082-112788

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=108315417&loc=d3e61044-112788

+ Details

Name:	us-gaap_LoansAndLeasesReceivableCommitmentsVariableRates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ffic_LetterOfCreditPledgedAsCollateralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ffic_CapitalSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ffic_FlushingFinancialsCapitalTrustsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_MortgagesMember
Namespace Prefix:
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Period Type:

Commitments and Contingencies (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Jul. 31, 2017	Jun. 30, 2017	Dec. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable, Commitments, Fixed Rates			$ 38.4
Loans and Leases Receivable, Commitments, Weighted Average Rate of Interest			3.82%
Loans and Leases Receivable, Commitments, Variable Rates			$ 436.7
Loans and Leases Receivable, Commitments, Variable Rates, Weighted Average Rate			3.84%
Loan Commitments, Expiration			90 days
Line of Credit, Maturity, Max			1 year 180 days
Purchase obligations			$ 17.4	$ 22.0
Home Equity Line of Credit [Member]
Loans and Leases Receivable, Commitments, Credit			$ 411.7
Line of Credit, Maturity, Max			10 years
Letter of Credit Pledged as Collateral [Member]
Deposit Liabilities, Collateral Issued, Financial Instruments			$ 855.4	$ 494.0
Capital Securities [Member] \| Flushing Financial's Capital Trusts [Member]
Proceeds from Issuance of Debt	$ 61.9	$ 61.9
Mortgages [Member]
Loans and Leases Receivable, Commitments, Credit			$ 62.4