Loans - Loans Modifications Made to Borrowers and Payment Status (Details) $ in Thousands	6 Months Ended
Jun. 30, 2025 USD ($) contract loan	Jun. 30, 2024 USD ($) contract
Term Extension and Reduced Interest Rate
Number of TDR loan modifications \| contract	1	1
Amortized Cost Basis	$ 8,400	$ 378
Payment Deferral \| Current
Amortized Cost Basis	48,562
Payment Deferral \| Total Modified
Amortized Cost Basis	$ 48,562
Multi-Family Residential
Number of TDR loan modifications \| loan	1
Multi-Family Residential \| Payment Deferral \| Current
Amortized Cost Basis	$ 7,473
Multi-Family Residential \| Payment Deferral \| Total Modified
Amortized Cost Basis	7,473
Commercial Business and Other \| Term Extension and Reduced Interest Rate
Number of TDR loan modifications \| contract		1
Amortized Cost Basis		$ 378
Decrease in interest rate		0.00%
Commercial Business and Other \| Payment Deferral \| Current
Amortized Cost Basis	7
Commercial Business and Other \| Payment Deferral \| Total Modified
Amortized Cost Basis	$ 7
Commercial Real Estate \| Term Extension and Reduced Interest Rate
Number of TDR loan modifications \| contract	1
Amortized Cost Basis	$ 8,400
Total Class of Financing Receivables, percentage	0.40%
Commercial Real Estate \| Term Extension and Reduced Interest Rate \| Minimum
Decrease in interest rate	6.00%
Commercial Real Estate \| Term Extension and Reduced Interest Rate \| Maximum
Decrease in interest rate	7.22%
Commercial Real Estate \| Payment Deferral \| Current
Amortized Cost Basis	$ 41,082
Commercial Real Estate \| Payment Deferral \| Total Modified
Amortized Cost Basis	$ 41,082

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

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ 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

+ Details

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

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: