Loans and Allowance for Credit Losses - Loans Modifications Made to Borrowers and Payment Status (Details) $ in Thousands	12 Months Ended
Dec. 31, 2024 USD ($) contract	Dec. 31, 2023 USD ($) contract
Term Extension and Reduced Interest Rate
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 378
Payment Deferral
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 2,793
Payment Deferral \| Current
Amortized Cost Basis	40,186
Payment Deferral \| Greater than 90 Days Past Due
Amortized Cost Basis	266
Payment Deferral \| Total Past Due
Amortized Cost Basis	$ 40,452
Other Than Insignificant Payment Delay
Number of TDR loan modifications \| contract	2	1
Amortized Cost Basis	$ 37,362	$ 1,488
Extended Maturity [Member]
Number of TDR loan modifications \| contract	1	3
Amortized Cost Basis	$ 8	$ 1,734
Multi-Family Residential \| Payment Deferral \| Current
Amortized Cost Basis	7,472
Multi-Family Residential \| Payment Deferral \| Total Past Due
Amortized Cost Basis	$ 7,472
Multi-Family Residential \| Other Than Insignificant Payment Delay
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 7,472
Total Class of Financing Receivables, percentage	0.30%
Payment deferral period	18 months
Commercial Business and Other \| Term Extension and Reduced Interest Rate
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 378
Commercial Business and Other \| Payment Deferral \| Current
Amortized Cost Basis	8
Commercial Business and Other \| Payment Deferral \| Greater than 90 Days Past Due
Amortized Cost Basis	266
Commercial Business and Other \| Payment Deferral \| Total Past Due
Amortized Cost Basis	$ 274
Commercial Business and Other \| Extended Maturity [Member]
Number of TDR loan modifications \| contract	1	3
Amortized Cost Basis	$ 8	$ 1,734
Total Class of Financing Receivables, percentage		0.10%
Small Business Administration \| Other Than Insignificant Payment Delay
Number of TDR loan modifications \| contract		1
Amortized Cost Basis		$ 1,488
Total Class of Financing Receivables, percentage		7.30%
Commercial Real Estate \| Payment Deferral
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 2,793
Total Class of Financing Receivables, percentage	0.10%
Commercial Real Estate \| Payment Deferral \| Current
Amortized Cost Basis	$ 32,706
Commercial Real Estate \| Payment Deferral \| Total Past Due
Amortized Cost Basis	$ 32,706
Commercial Real Estate \| Other Than Insignificant Payment Delay
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 29,890
Total Class of Financing Receivables, percentage	1.50%

Number of financing receivable that have been modified by troubled debt restructurings to borrowers experiencing financial difficulty.

No definition available.

+ Details

Name:	ffic_FinancingReceivableModificationsMadeToBorrowersExperiencingFinancialDifficultyNumberOfContracts
Namespace Prefix:	ffic_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Percentage, excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesExcludingAccruedInterestPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of payment deferral of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableModifiedPaymentDeferralPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=ffic_ContractualInterestRateReductionAndExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=ffic_OtherThanInsignificantPaymentDelayMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ffic_MultiFamilyResidentialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ffic_CommercialBusinessAndOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=ffic_SmallBusinessAdministrationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: