Note 16 - Subsequent Events (Details Textual) $ / shares in Units, $ in Thousands	Oct. 24, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Assets, Total		$ 7,110,895	$ 6,834,176
Deposits, Total		$ 4,912,509	$ 4,915,923
Subsequent Event [Member]
Assets, Total	$ 8,000,000
Loans and Leases Receivable, Gross, Total	6,300,000
Deposits, Total	$ 5,800,000
Number of Branches	23
Empire Bancorp, Inc. [Member] \| Subsequent Event [Member]
Business Combination, Consideration Transferred, Total	$ 111,600
Business Combination, Number of Common Shares Exchanged, Per Share	0.6548
Business Combination, Equity Interest Issued or Issuable, Per Share, Cash \| $ / shares	$ 14.04
Business Combination, Percent Acquired, Common Stock	50.00%
Business Combination, Percent Acquired, Cash	50.00%

The cash per share amount of equity interest in a business combination.

No definition available.

Name:	ffic_BusinessCombinationEquityInterestIssuedOrIssuablePerShareCash
Namespace Prefix:	ffic_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of common shares exchanged, per company common stock shares, in a business combination.

+ References

No definition available.

+ Details

Name:	ffic_BusinessCombinationNumberOfCommonSharesExchangedPerShare
Namespace Prefix:	ffic_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The percent in a business combination of cash used in the transaction.

+ References

No definition available.

+ Details

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

- Definition

The percent in a business combination of common stock used in the transaction.

+ References

No definition available.

+ Details

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

- Definition

The number of branches.

+ References

No definition available.

+ Details

Name:	ffic_NumberOfBranches
Namespace Prefix:	ffic_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

+ Details

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

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ffic_EmpireBancorpIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: