Financing Receivable, Modifications, Specific Reserves Allocated to Troubled Debt Restructuring

No definition available.

Name:	thff_FinancingReceivableModificationsSpecificReservesAllocatedtoTroubledDebtRestructuring
Namespace Prefix:	thff_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the minimum outstanding balance of loans to be individually reviewed and classified as to credit risk. Homogeneous loans (at all levels of outstanding balances) are not reviewed individually, but rather as part of a group.

+ References

No definition available.

+ Details

Name:	thff_LoansAndLeasesReceivableMinimumOutstandingBalanceToBeIndividuallyEvaluated
Namespace Prefix:	thff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

+ Details

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

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

+ Details

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

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953550-111524

+ Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_CommercialAndIndustrialReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_FarmlandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_CoveredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_NonFarmNonResidentialReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_AgricultureReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_OtherCommercialReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_FirstMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_SecondMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_OtherResidentialReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_AutomobileLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=thff_OtherConsumerReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Allowance for Loan Losses (Details Textual) - USD ($)	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Allowance for loan losses
Financing Receivable, Modifications, Specific Reserves Allocated to Troubled Debt Restructuring			$ 24,000
Fair value	$ 6,863,000	$ 8,600,000
Minimum outstanding balance of non-homogeneous loans to be individually evaluated as to credit risk	100,000
Commercial & Industrial
Allowance for loan losses
Fair value	365,000	501,000
Farmland
Allowance for loan losses
Fair value	0	0
Covered Loans
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing		80,000
Nonaccrual	85,000	112,000
Non Farm, Non Residential
Allowance for loan losses
Fair value	0	451,000
Agriculture
Allowance for loan losses
Fair value	0	0
All Other Commercial
Allowance for loan losses
Fair value	0	0
First Liens
Allowance for loan losses
Fair value	435,000	435,000
Home Equity
Allowance for loan losses
Fair value	0	0
Junior Liens
Allowance for loan losses
Fair value	0	0
Multifamily
Allowance for loan losses
Fair value	0	0
All Other Residential
Allowance for loan losses
Fair value	0	0
Motor Vehicle
Allowance for loan losses
Fair value	0	0
All Other Consumer
Allowance for loan losses
Fair value	0	0
Nonperforming Financing Receivable [Member]
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	512,000	669,000
Nonaccrual	11,106,000	13,492,000
Nonperforming Financing Receivable [Member] \| Commercial & Industrial
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	45,000
Nonaccrual	2,155,000	2,405,000
Nonperforming Financing Receivable [Member] \| Farmland
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	104,000	978,000
Nonperforming Financing Receivable [Member] \| Non Farm, Non Residential
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	311,000	1,027,000
Nonperforming Financing Receivable [Member] \| Agriculture
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	595,000	744,000
Nonperforming Financing Receivable [Member] \| All Other Commercial
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	1,352,000	1,380,000
Nonperforming Financing Receivable [Member] \| First Liens
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	143,000	276,000
Nonaccrual	5,024,000	5,496,000
Nonperforming Financing Receivable [Member] \| Home Equity
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	271,000	285,000
Nonperforming Financing Receivable [Member] \| Junior Liens
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	55,000
Nonaccrual	230,000	202,000
Nonperforming Financing Receivable [Member] \| Multifamily
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	0	0
Nonaccrual	0	0
Nonperforming Financing Receivable [Member] \| All Other Residential
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	12,000	0
Nonaccrual	91,000	94,000
Nonperforming Financing Receivable [Member] \| Motor Vehicle
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	336,000	293,000
Nonaccrual	211,000	140,000
Nonperforming Financing Receivable [Member] \| All Other Consumer
Allowance for loan losses
Loans Past Due Over 90 Day Still Accruing	21,000	0
Nonaccrual	$ 762,000	$ 741,000