Note 6 - Loans Held for Sale - Delinquent and Non-performing Loans Sold During the Period Indicated (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Nonperforming Financial Instruments [Member]
Loans sold	6	8	12	14
Proceeds	$ 4,210	$ 2,738	$ 8,739	$ 4,863
Net (charge-offs) recoveries	68		68	(37)
Net gain (loss)	$ 10	$ 179	$ (225)	$ 208
Nonperforming Financial Instruments [Member] \| Multi-family Residential Portfolio Segment [Member]
Loans sold	1	2	4	2
Proceeds	$ 595	$ 707	$ 1,559	$ 707
Net (charge-offs) recoveries
Net gain (loss)		$ 30		$ 30
Nonperforming Financial Instruments [Member] \| Commercial Real Estate Portfolio Segment [Member]
Loans sold	1	3	4	4
Proceeds	$ 2,500	$ 1,118	$ 6,065	$ 1,453
Net (charge-offs) recoveries				(4)
Net gain (loss)		$ 34	$ (235)	$ 35
Nonperforming Financial Instruments [Member] \| One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
Loans sold	2	3	2	8
Proceeds	$ 725	$ 913	$ 725	$ 2,703
Net (charge-offs) recoveries	(4)		(4)	(33)
Net gain (loss)		$ 115		$ 143
Nonperforming Financial Instruments [Member] \| One-To-Four Family - Residential Portfolio Segment [Member]
Loans sold	2		2
Proceeds	$ 390		$ 390
Net (charge-offs) recoveries	72		72
Net gain (loss)	$ 10		$ 10
Performing Financial Instruments [Member]
Loans sold		13	9	27
Proceeds		$ 30,678	$ 5,671	$ 50,128
Net gain (loss)		$ (27)	393	188
Net (charge-offs) recoveries
Performing Financial Instruments [Member] \| Multi-family Residential Portfolio Segment [Member]
Loans sold		10		12
Proceeds		$ 12,704		$ 18,784
Net gain (loss)		$ (22)		(36)
Net (charge-offs) recoveries
Performing Financial Instruments [Member] \| Commercial Real Estate Portfolio Segment [Member]
Loans sold		2		7
Proceeds		$ 17,832		$ 26,283
Net gain (loss)		$ (7)		(28)
Net (charge-offs) recoveries
Performing Financial Instruments [Member] \| Small Business Administration Portfolio Segment [Member]
Loans sold		1	9	8
Proceeds		$ 142	$ 5,671	$ 5,061
Net gain (loss)		$ 2	393	252
Net (charge-offs) recoveries

The amount of charge-offs (recoveries) of loans held for sale.

No definition available.

Name:	ffic_ChargeoffsRecoveriesOfLoansHeldForSale
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of net recoveries (charge-offs) during the period on delinquent and non-performing loans during the period.

+ References

No definition available.

+ Details

Name:	ffic_DelinquentAndNonPerformingLoansNetRecoveriesChargeOffs
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Proceeds from the sales of delinquent and non-performing loans sold during the period.

+ References

No definition available.

+ Details

Name:	ffic_DelinquentAndNonPerformingLoansProceeds
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Delinquent and non-performing loans sold during the period.

+ References

No definition available.

+ Details

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

- Definition

Net gain (loss) on delinquent and non-performing loans during the period.

+ References

No definition available.

+ Details

Name:	ffic_DelinquentAndNonperformingLoansNetGainLoss
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of gain (loss) realized from the sale of loans held for sale.

+ References

No definition available.

+ Details

Name:	ffic_GainLossOnSaleOfLoansHeldForSale
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of loans sold during the period that were held for sale.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow resulting from the sale of loans classified as held-for-sale, including proceeds from loans sold through mortgage securitization.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3337-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3461-108585

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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