Additional terms of contract stating automatic extension of contract at expiration date.

No definition available.

Name:	flic_AdditionalTermsOfContract
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	flic_EmploymentContractsAbstract
Namespace Prefix:	flic_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum extended period of employment contract to get the automatic extension of contract at expiration date.

+ References

No definition available.

+ Details

Name:	flic_ExtendedPeriodOfEmploymentContract
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Expiration period of financial instruments, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

No definition available.

+ Details

Name:	flic_FinancialInstrumentsOffBalanceSheetRisksExpirationPeriod
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maturity period of financial instruments, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

No definition available.

+ Details

Name:	flic_FinancialInstrumentsOffBalanceSheetRisksMaturityPeriod
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of base rent on lease from related party.

+ References

No definition available.

+ Details

Name:	flic_LeaseBaseRentPaidToRelatedParty
Namespace Prefix:	flic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Properties leased from related party that the bank pays proportionate share of real estate taxes.

+ References

No definition available.

+ Details

Name:	flic_LeasedPropertiesWithProportionateShareOfRealEstateTaxes
Namespace Prefix:	flic_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of buildings occupied and leased from related party.

+ References

No definition available.

+ Details

Name:	flic_NumberOfBuildingsLeasedFromRelatedParty
Namespace Prefix:	flic_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of collateral held for commitments or guarantees.

+ References

No definition available.

+ Details

Name:	flic_PercentageOfCollateralHeldForCommitments
Namespace Prefix:	flic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The minimum duration of employment contract.

+ References

No definition available.

+ Details

Name:	flic_TermsOfEmploymentContractLowerRange
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum duration of employment contract.

+ References

No definition available.

+ Details

Name:	flic_TermsOfEmploymentContractUpperRange
Namespace Prefix:	flic_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Rental expense incurred for leased assets including furniture and equipment which has not been recognized in costs and expenses applicable to sales and revenues; for example, cost of goods sold or other operating costs and expenses.

+ References

No definition available.

+ Details

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

- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

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

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

No definition available.

+ Details

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

- Definition

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 16

-Subparagraph b(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 122

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 3)

-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

+ Details

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

- Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of required minimum rental payments maturing in the next fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments maturing in the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments maturing in the forth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments maturing in the third fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments maturing in the second fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments maturing after the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenditures for salaries for officers and non-officers. Does not include allocated share-based compensation, pension and post-retirement benefit expense or other labor-related non-salary expense. For commercial and industrial companies, excludes any direct and overhead labor that is included in cost of goods sold.

+ References

No definition available.

+ Details

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

COMMITMENTS AND CONTINGENT LIABILITIES (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employment Contracts [Abstract]
Terms of employment contract, lower range	6 months
Terms of employment contract, upper range	3 years
Extended period of employment contract	18 months
Additional terms of contract	1 year
Current aggregate annual salaries	$ 1,687,500
Minimum annual rental commitments under non-cancelable operating leases [Abstract]
2013	1,294,000
2014	1,145,000
2015	1,008,000
2016	868,000
2017	785,000
Thereafter	3,103,000
Operating leases, future minimum payments due	8,203,000
Rental expense, real estate taxes, and common are maintenance	1,531,000	1,515,000	1,431,000
Related Party Leases [Abstract]
Number of buildings leased from related party	2
Lease base rent paid to related party	67,000	67,000	66,000
Leased properties with proportionate share of real estate taxes	1
Minimum [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed interest rate (in hundredths)	2.75%
Maturity period of fixed rate loan commitment	5 years
Percentage of collateral held for commitments (in hundredths)	0.00%
Maximum [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed interest rate (in hundredths)	4.00%
Percentage of collateral held for commitments (in hundredths)	100.00%
Average [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Percentage of collateral held for commitments (in hundredths)	88.00%
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed rate	8,420,000	14,479,000
Variable rate	159,313,000	123,877,000
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed rate	5,961,000	4,334,000
Variable rate	0	0
Commercial Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed rate	87,000	63,000
Variable rate	$ 0	$ 0
Home Equity Lines [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments off balance sheet risk expiration period	10 years
Other Real Estate Loan Commitment [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments off balance sheet risk expiration period	60 days
Commercial Loan Commitments [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments off balance sheet risk expiration period	1 year