Loans - Non-Accrual at Amortized Cost (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Total Non-accrual amortized cost	$ 30,917	$ 15,253	$ 20,947
Non-Accrual with no related Allowance	14,874	13,613
Interest income recognized	139	104
Loans ninety days or more past due and still accruing:	100
Multi-family Residential Portfolio Segment [Member]
Total Non-accrual amortized cost	3,707	2,652	2,576
Non-Accrual with no related Allowance	3,707	2,652
Interest income recognized		19
Commercial Real Estate
Total Non-accrual amortized cost	273	640	1,766
Non-Accrual with no related Allowance	273	640
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
Total Non-accrual amortized cost	1,049	1,582	1,706
Non-Accrual with no related Allowance	1,049	1,582
Interest income recognized		6
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] \| Performing Financial Instruments [Member]
Non-accrual loans	300	300
One-To-Four Family - Residential Portfolio Segment [Member]
Total Non-accrual amortized cost	4,708	7,482	5,313
Non-Accrual with no related Allowance	4,708	7,482
Interest income recognized		1
Construction Portfolio Segment [Member]
Total Non-accrual amortized cost	856
Non-Accrual with no related Allowance	856
Small Business Administration Portfolio Segment [Member]
Total Non-accrual amortized cost	951	952	1,168
Non-Accrual with no related Allowance	951	952
Taxi Medallion Portfolio Segment [Member]
Total Non-accrual amortized cost			2,758
Commercial Business and Other Portfolio Segment [Member]
Total Non-accrual amortized cost	19,373	1,945	$ 5,660
Non-Accrual with no related Allowance	3,330	305
Interest income recognized	139	78
Loans ninety days or more past due and still accruing:	100
Commercial Business and Other Portfolio Segment [Member] \| Performing Financial Instruments [Member]
Non-accrual loans	$ 2,800
Commercial Business and Other Portfolio Segment [Member] \| Performing Financial Instruments [Member] \| Maximum [Member]
Non-accrual loans		$ 100

Amount of financing receivable on nonaccrual status at amortized cost.

No definition available.

Name:	ffic_FinancingReceivableNonaccrualAmortizedCost
Namespace Prefix:	ffic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

+ Details

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

- Definition

Amount of financing receivable on nonaccrual status with no allowance for credit loss.

+ References

+ Details

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

- Definition

Amount of financing receivable 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922355-210448

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

+ Details

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

- 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_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
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_FinancingReceivablePortfolioSegmentAxis=ffic_ConstructionPortfolioSegmentMember
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:

- Details

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

- Details

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

- Details

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