Represents the number of approaches followed to determine the final fair value.

No definition available.

Name:	thff_NumberOfApproachesFollowedToDetermineFinalFairValue
Namespace Prefix:	thff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of impaired loans.

+ References

No definition available.

+ Details

Name:	thff_NumberOfImpairedLoans
Namespace Prefix:	thff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of methods to derive value under the appraisals for real estate.

+ References

No definition available.

+ Details

Name:	thff_NumberOfMethodsToDeriveValueUnderAppraisalsForRealEstateTechnique
Namespace Prefix:	thff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the provision for impaired loan losses.

+ References

No definition available.

+ Details

Name:	thff_ProvisionForImpairedLoanLosses
Namespace Prefix:	thff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

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

- Details

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

- Definition

Ratio of the net operating income produced by an asset and its capital cost (original prices paid to buy the asset), used as an input to measure fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsCapRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of likelihood a loan will not be repaid and instead default, used as an input to measure fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsProbabilityOfDefault
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

+ Details

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

Fair Value (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2012 item	Dec. 31, 2011
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Valuation allowance for impaired loans	$ 5,680	$ 5,680	$ 4,273
Provision for impaired loan losses	(1,100)	(1,800)	(3,300)
Number of approaches followed to determine final fair value		3
Sales comparison/income approach
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Capitalization rate applied to projected net operating income (as a percent)		9.50%
Other real estate
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Number of methods to derive value under appraisals for real estate		3
Impaired loan collateralized by hotel
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Fair Value	5,300	5,300
Number of impaired loans		1
Level 3
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Fair Value	8,670	8,670	4,964
Valuation allowance for impaired loans	5,680	5,680	4,273
Level 3 \| State and Municipal Obligations
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Fair Value	9,911	9,911
Level 3 \| State and Municipal Obligations \| Discounted cash flow
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Probability of default (as a percent)		0.00%
Level 3 \| State and Municipal Obligations \| Discounted cash flow \| Minimum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		3.05%
Level 3 \| State and Municipal Obligations \| Discounted cash flow \| Maximum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		5.50%
Level 3 \| Other real estate
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Fair Value	8,670	8,670
Level 3 \| Other real estate \| Sales comparison/income approach \| Minimum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		5.00%
Level 3 \| Other real estate \| Sales comparison/income approach \| Maximum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		20.00%
Level 3 \| Impaired Loans
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Fair Value	28,984	28,984	28,400
Valuation allowance for impaired loans	$ 5,700	$ 5,700	$ 4,300
Level 3 \| Impaired loan collateralized by hotel \| Sales comparison/income approach \| Minimum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		0.00%
Level 3 \| Impaired loan collateralized by hotel \| Sales comparison/income approach \| Maximum
Quantitative information about recurring and non-recurring Level 3 fair value measurements
Discount rate (as a percent)		50.00%