SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2013
Basis of Presentation Policy	The Consolidated Financial Statements of First Financial, a bank holding company principally serving Ohio, Indiana and Kentucky, include the accounts and operations of First Financial and its wholly-owned subsidiary – First Financial Bank, N.A. (First Financial Bank or the Bank). All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior periods’ amounts have been made to conform to the current period’s presentation and had no effect on net earnings.
Use of Estimates, Policy	The preparation of financial statements in conformity with U.S. Generally Accepted Accounting Principles (GAAP) requires management to make estimates, assumptions and judgments that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes. Actual realized amounts could differ materially from those estimates.
Goodwill and Intangible Assets, Goodwill, Policy	Goodwill. Assets and liabilities of acquired entities are recorded at their estimated fair values as of the acquisition date. The excess cost of the acquisition over the fair value of net assets acquired is recorded as goodwill. Goodwill is not amortized, but is measured for impairment on an annual basis as of October 1 of each year or whenever events or changes in circumstances indicate that the fair value of a reporting unit may be below its carrying value.
Goodwill and Intangible Assets, Policy	Other intangible assets. Other intangible assets consist primarily of core deposit intangibles. Core deposit intangibles are recorded at their estimated fair value as of the acquisition date and are then amortized on an accelerated basis over their estimated useful lives.
Commitments and Contingencies, Policy	In the normal course of business, First Financial offers a variety of financial instruments with off-balance-sheet risk to its clients to assist them in meeting their requirements for liquidity and credit enhancement. These financial instruments include standby letters of credit and outstanding commitments to extend credit. GAAP does not require these financial instruments to be recorded in the Consolidated Financial Statements. First Financial’s exposure to credit loss, in the event of nonperformance by the other party to the financial instrument for standby letters of credit, and outstanding commitments to extend credit, is represented by the contractual amounts of those instruments. First Financial uses the same credit policies in issuing commitments and conditional obligations as it does for credit instruments recorded on the Consolidated Balance Sheets.
Certain Loans and Debt Securities Acquired in Transfer, Recognizing Interest Income on Impaired Loans, Policy	First Financial accounts for the majority of covered loans under FASB ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality, except loans with revolving privileges, which are outside the scope of this guidance, and loans for which cash flows could not be estimated, which are accounted for under the cost recovery method. Loans accounted for under FASB ASC Topic 310-30 are referred to as purchased impaired loans. Purchased impaired loans are not classified as nonperforming assets as the loans are considered to be performing under FASB ASC Topic 310-30. Therefore, interest income, through accretion of the difference between the carrying value of the loans and the expected cash flows (accretable difference) is recognized on all covered purchased impaired loans.
Fair Value of Financial Instruments, Policy	Fair Value Measurement The fair value framework as disclosed in the Fair Value Measurements and Disclosure Topic of FASB ASC Topic 825, Financial Instruments (Fair Value Topic) includes a hierarchy which focuses on prioritizing the inputs used in valuation techniques. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), a lower priority to observable inputs other than quoted prices in active markets for identical assets and liabilities (Level 2) and the lowest priority to unobservable inputs (Level 3). When determining the fair value measurements for assets and liabilities, First Financial looks to active markets to price identical assets or liabilities whenever possible and classifies such items in Level 1. When identical assets and liabilities are not traded in active markets, First Financial looks to observable market data for similar assets and liabilities and classifies such items as Level 2. Certain assets and liabilities are not actively traded in observable markets and First Financial must use alternative techniques, based on unobservable inputs, to determine the fair value and classifies such items as Level 3. The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement. The following methods, assumptions and valuation techniques were used by First Financial to measure different financial assets and liabilities at fair value and in estimating its fair value disclosures for financial instruments. Cash and short-term investments. The carrying amounts reported in the Consolidated Balance Sheets for cash and short-term investments, such as federal funds sold, approximated the fair value of those instruments. The Company classifies cash and short-term investments in Level 1 of the fair value hierarchy. Investment securities. Investment securities classified as trading and available-for-sale are recorded at fair value on a recurring basis. Fair value measurement is based upon quoted market prices, when available (Level 1). If quoted market prices are not available, fair values are measured utilizing independent valuation techniques of identical or similar investment securities. First Financial compiles prices from various sources who may apply such techniques as matrix pricing to determine the value of identical or similar investment securities (Level 2). Matrix pricing is a mathematical technique widely used in the banking industry to value investment securities without relying exclusively on quoted prices for the specific investment securities but rather relying on the investment securities’ relationship to other benchmark quoted investment securities. Any investment securities not valued based upon the methods above are considered Level 3. First Financial utilizes information provided by a third-party investment securities administrator in analyzing the investment securities portfolio in accordance with the fair value hierarchy of the Fair Value Topic. The administrator’s evaluation of investment security portfolio pricing is performed using a combination of prices and data from other sources, along with internally developed matrix pricing models and assistance from the administrator’s internal fixed income analysts and trading desk. The administrator’s month-end pricing process includes a series of quality assurance activities where prices are compared to recent market conditions, previous evaluation prices and between the various pricing services. These processes produce a series of quality assurance reports on which price exceptions are identified, reviewed and where appropriate, securities are repriced. In the event of a materially different price, the administrator will report the variance as a “price challenge” and review the pricing methodology in detail. The results of the quality assurance process are incorporated into the selection of pricing providers by the portfolio manager. First Financial reviews the pricing methodologies utilized by the administrator to ensure the fair value determination is consistent with the applicable accounting guidance and that the investments are properly classified in the fair value hierarchy. Further, the Company periodically validates the fair values for a sample of securities in the portfolio by comparing the fair values provided by the administrator to prices from other independent sources for the same or similar securities. First Financial analyzes unusual or significant variances, conducts additional research with the administrator, if necessary, and takes appropriate action based on its findings. Loans held for sale. Loans held for sale are carried at the lower of cost or fair value. These loans currently consist of one-to-four family residential real estate loans originated for sale to qualified third parties. Fair value is based on the contractual price to be received from these third parties, which is not materially different than cost due to the short duration between origination and sale (Level 2). As such, First Financial records any fair value adjustments on a nonrecurring basis. Gains and losses on the sale of loans are recorded as net gains from sales of loans within noninterest income in the Consolidated Statements of Income. Loans - excluding covered loans. The fair value of commercial, commercial real estate, residential real estate and consumer loans were estimated by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities or repricing frequency. The Company classifies the estimated fair value of uncovered loans as Level 3 in the fair value hierarchy. Loans are designated as impaired when, in the judgment of management based on current information and events, it is probable that all amounts due according to the contractual terms of the loan agreement will not be collected. Impaired loans are valued at the lower of cost or fair value for purposes of determining the appropriate amount of impairment to be allocated to the allowance for loan and lease losses. Fair value is generally measured based on the value of the collateral securing the loans. Collateral may be in the form of real estate or business assets including equipment, inventory and accounts receivable. The vast majority of the collateral is real estate. The value of real estate collateral is determined utilizing an income or market valuation approach based on an appraisal conducted by an independent, licensed third party appraiser (Level 3). The value of business equipment is based upon an outside appraisal if deemed significant, or the net book value on the applicable borrower financial statements if not considered significant. Likewise, values for inventory and accounts receivable collateral are based on borrower financial statement balances or aging reports on a discounted basis as appropriate (Level 3). Impaired loans allocated to the allowance for loan and lease losses are measured at fair value on a nonrecurring basis. Any fair value adjustments are recorded in the period incurred as provision for loan and lease losses on the Consolidated Statements of Income. Covered loans. Fair values for covered loans accounted for under FASB ASC Topic 310-30 are based on a discounted cash flow methodology that considers factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of the loan and whether or not the loan was amortizing and a discount rate reflecting the Company's assessment of risk inherent in the cash flow estimates. These covered loans are grouped together according to similar characteristics and were treated in the aggregate when applying various valuation techniques. First Financial estimated the cash flows expected to be collected on these loans based upon the expected remaining life of the underlying loans, which includes the effects of estimated prepayments. These cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. Fair values for covered loans accounted for outside of FASB ASC Topic 310-30 were estimated by discounting the future cash flows using current interest rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities or repricing frequency. The carrying amount of accrued interest approximates its fair value. The Company classifies the estimated fair value of covered loans as Level 3 in the fair value hierarchy. FDIC indemnification asset. The accounting for FDIC indemnification assets is closely related to the accounting for the underlying, indemnified assets. Fair value of the FDIC indemnification asset was estimated using projected cash flows related to the loss sharing agreements based on the expected reimbursements for losses and the applicable loss sharing percentages. First Financial re-estimates the expected indemnification asset cash flows in conjunction with the periodic re-estimation of cash flows on covered loans accounted for under FASB ASC Topic 310-30. Improvements in cash flow expectations on covered loans generally result in a related decline in the expected indemnification cash flows while declines in cash flow expectations on covered loans generally result in an increase in expected indemnification cash flows. The expected cash flows are discounted to reflect the uncertainty of the timing and receipt of the loss sharing reimbursement from the FDIC. These cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. The Company classifies the estimated fair value of the indemnification asset as Level 3 in the fair value hierarchy. Deposit liabilities. The fair value of demand deposits, savings accounts and certain money-market deposits was the amount payable on demand at the reporting date. The carrying amounts for variable-rate certificates of deposit approximated their fair values at the reporting date. The fair value of fixed-rate certificates of deposit was estimated using a discounted cash flow calculation which applies the interest rates currently offered for deposits of similar remaining maturities. The carrying amount of accrued interest approximates its fair value. The Company classifies the estimated fair value of deposit liabilities as Level 2 in the fair value hierarchy. Borrowings. The carrying amounts of federal funds purchased and securities sold under agreements to repurchase and other short-term borrowings approximate their fair values. The Company classifies the estimated fair value of short-term borrowings as Level 1 of the fair value hierarchy. The fair value of long-term debt is estimated using a discounted cash flow calculation which utilizes the interest rates currently offered for borrowings of similar remaining maturities. Third-party valuations are used for long-term debt with embedded options, such as call features. The Company classifies the estimated fair value of long-term debt as Level 2 in the fair value hierarchy. Commitments to extend credit and standby letters of credit. Pricing of these financial instruments is based on the credit quality and relationship, fees, interest rates, probability of funding and compensating balance and other covenants or requirements. Loan commitments generally have fixed expiration dates, are variable rate and contain termination and other clauses which provide for relief from funding in the event that there is a significant deterioration in the credit quality of the client. Many loan commitments are expected to expire without being drawn upon. The rates and terms of the commitments to extend credit and the standby letters of credit are competitive with those in First Financial’s market area. The carrying amounts are reasonable estimates of the fair value of these financial instruments. Carrying amounts, which are comprised of the unamortized fee income and, where necessary, reserves for any expected credit losses from these financial instruments, are immaterial. Derivatives. The fair values of derivative instruments are based primarily on a net present value calculation of the cash flows related to the interest rate swaps at the reporting date, using primarily observable market inputs such as interest rate yield curves. The discounted net present value calculated represents the cost to terminate the swap if First Financial should choose to do so. Additionally, First Financial utilizes a vendor-developed, proprietary model to value the credit risk component of both the derivative assets and liabilities. The credit valuation adjustment is recorded as an adjustment to the fair value of the derivative asset or liability on the reporting date. Derivative instruments are classified as Level 2 in the fair value hierarchy.
Credit Risk
Derivatives, Methods of Accounting, Hedging Derivatives	First Financial manages the market value credit risk associated with counterparties through counterparty credit policies. These policies require the Company to maintain a total derivative notional position of less than 35% of assets, total credit exposure of less than 3% of capital and no single counterparty credit risk exposure greater than $20.0 million.
Non Covered Loans
Loans and Leases Receivable, Nonaccrual Loan and Lease Status, Policy	Loans are classified as nonaccrual when, in the opinion of management, collection of principal or interest is doubtful or when principal or interest payments are ninety days or more past due. Generally, loans are classified as nonaccrual due to the continued failure to adhere to contractual payment terms by the borrower coupled with other pertinent factors such as insufficient collateral value. The accrual of interest income is discontinued and previously accrued, but unpaid interest is reversed when a loan is classified as nonaccrual. Any payments received while a loan is on nonaccrual status are applied as a reduction to the carrying value of the loan. A loan may be reclassified back to accrual status if all contractual payments have been received and collection of future principal and interest payments is no longer doubtful.
Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block]	A loan modification is considered a TDR when two conditions are met: 1) the borrower is experiencing financial difficulty and 2) concessions are made by the Company that would not otherwise be considered for a borrower with similar credit characteristics. The most common types of modifications include interest rate reductions, maturity extensions and modifications to principal amortization, including interest only structures. Modified terms are dependent upon the financial position and needs of the individual borrower. If the modification agreement is violated, the loan is managed by the Company’s credit administration group for resolution, which may result in foreclosure in the case of real estate. TDRs are generally classified as nonaccrual for a minimum period of six months and may qualify for return to accrual status once they have demonstrated performance with the terms of the loan modification.
Impaired Financing Receivable, Policy	Loans classified as nonaccrual and loans modified as TDRs are considered impaired. First Financial individually reviews all impaired commercial loan relationships greater than $250,000, as well as consumer loan TDRs greater than $100,000, to determine if a specific allowance based on the borrower’s overall financial condition, resources and payment record, support from guarantors and the realizable value of any collateral is necessary. Specific allowances are based on expected cash flows, discounted using the loan's initial effective interest rate or the fair value of the collateral for certain collateral dependent loans.
Loans and Leases Receivable, Real Estate Acquired Through Foreclosure, Policy	Other real estate owned (OREO) is comprised of properties acquired by the Company through the loan foreclosure or repossession process, or other resolution activity that results in partial or total satisfaction of problem loans. The acquired properties are recorded at the lower of cost or fair value less estimated costs of disposal (net realizable value) upon acquisition. Losses arising at the time of acquisition of such properties are charged against the allowance for loan and lease losses. Subsequent write-downs in the carrying value of OREO properties are expensed as incurred. Improvements to the properties may be capitalized if the improvements contribute to the overall value of the property, but may not be capitalized in excess of the net realizable value of the property.
Loans and Leases Receivable, Allowance for Loan Losses Policy	For each reporting period, management maintains the allowance for loan and lease losses at a level that it considers sufficient to absorb probable loan and lease losses inherent in the portfolio. Management determines the adequacy of the allowance based on historical loss experience as well as other significant factors such as composition of the portfolio, economic conditions, geographic footprint, the results of periodic internal and external evaluations of delinquent, nonaccrual and classified loans and any other adverse situations that may affect a specific borrower's ability to repay (including the timing of future payments). This evaluation is inherently subjective as it requires utilizing material estimates that may be susceptible to significant change. In the commercial portfolio, which includes commercial loans, construction and commercial real estate loans and lease financing, impaired loan relationships greater than $250,000 are evaluated to determine the need for a specific allowance based on the borrower's overall financial condition, resources and payment record, support from guarantors and the realizable value of any collateral. Loans are considered impaired when, in the judgment of management, based on current information and events, it is probable that all amounts due according to the contractual terms of the loan agreement will not be collected. The allowance for non-impaired commercial loans and impaired commercial loan relationships less than $250,000 includes a process of estimating the probable losses inherent in the portfolio by category, based on First Financial's internal system of credit risk ratings and historical loss data. These estimates may also be adjusted for management's estimate of probable losses on specific loan types dependent upon trends in the values of the underlying collateral, delinquent and nonaccrual loans, prevailing economic conditions, changes in lending strategies and other influencing factors. With the exception of loans modified as TDRs, consumer loans are evaluated by loan type (i.e. residential real estate, installment, etc.), as these loans exhibit homogeneous characteristics. The allowance for consumer loans, which includes residential real estate, installment, home equity, credit card loans and overdrafts, is established by estimating losses inherent in each particular category of consumer loans. The estimate of losses is primarily based on historical loss rates for each category, as well as trends in delinquent and nonaccrual loans, prevailing economic conditions and other significant influencing factors. Consumer loans modified as TDRs greater than $100,000 are individually reviewed to determine if a specific allowance is necessary. There were no material changes to First Financial's accounting policies or methodology related to the allowance for loan and lease losses during the first nine months of 2013, however certain modifications were made to the estimation process in the third quarter of 2012 to place greater emphasis on quantitative factors such as historical loan losses and less emphasis on qualitative factors. This resulted in a shift in the allocation of the allowance between certain consumer and commercial loan types but had no significant impact on the total allowance for loan and lease losses at September 30, 2013. The allowance is increased by provision expense and decreased by actual charge-offs, net of recoveries of amounts previously charged-off. First Financial's policy is to charge-off all or a portion of a loan when, in management's opinion, it is unlikely to collect the principal amount owed in full either through payments from the borrower or from the liquidation of collateral.
Covered Loans
Loans and Leases Receivable, Real Estate Acquired Through Foreclosure, Policy	Covered OREO is comprised of properties acquired by the Company through the loan foreclosure or repossession process, or other resolution activities that result in partial or total satisfaction of problem covered loans. These properties remain subject to loss sharing agreements whereby the FDIC reimburses First Financial for the majority of any losses incurred. The acquired properties are recorded at the lower of cost or fair value upon acquisition. Losses arising at the time of acquisition of such properties are charged against the allowance for loan and lease losses. Subsequent write-downs in the carrying value of covered OREO properties are expensed as incurred. Estimated reimbursements due from the FDIC under loss sharing agreements related to any losses upon acquisition or subsequent write-downs in the carrying value of covered OREO are recorded as noninterest income and an increase to the FDIC indemnification asset in the same period. Improvements to the properties may be capitalized if the improvements contribute to the overall value of the property, but may not be capitalized in excess of the net realizable value of the property.
Loans and Leases Receivable, Allowance for Loan Losses Policy	First Financial performs periodic valuation procedures to re-estimate the expected cash flows on covered loans accounted for under FASB ASC Topic 310-30 and compare the present value of expected cash flows to the carrying value of the loans at the pool level. In order to estimate expected cash flows, First Financial specifically reviews a sample of these covered loans to assist in the determination of appropriate probability of default and loss given default assumptions to be applied to the remainder of the portfolio. The estimate of expected cash flows may also be adjusted for management's estimate of probable losses on specific loan types dependent upon trends in observable market and industry data, such as prepayment speeds and collateral values. Additionally, during the second quarter of 2013, the Company implemented certain enhancements to its valuation methodology and the estimation of impairment to place greater emphasis on changes in total expected cash flows and less emphasis on changes in the net present value of expected cash flows. These cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change.
Covered Loans \| Loans Accounted for Under FASB ASC Topic 310-30
Loans and Leases Receivable, Nonperforming Loan and Lease, Policy	Covered purchased impaired loans are classified as performing, even though they may be contractually past due, as any nonpayment of contractual principal or interest is considered in the periodic re-estimation of expected cash flows and is included in the resulting recognition of current period covered loan loss provision or prospective yield adjustments.
Covered Loans \| Loans Excluded from FASB ASC Topic 310-30
Loans and Leases Receivable, Nonperforming Loan and Lease, Policy	Similar to uncovered loans, covered loans accounted for outside FASB ASC Topic 310-30 are classified as nonaccrual when, in the opinion of management, collection of principal or interest is doubtful or when principal or interest payments are ninety days or more past due. Generally, these loans are classified as nonaccrual due to the continued failure to adhere to contractual payment terms by the borrower coupled with other pertinent factors, such as insufficient collateral value. The accrual of interest income is discontinued and previously accrued, but unpaid interest is reversed when a loan is classified as nonaccrual. Any payments received while a loan is classified as nonaccrual are applied as a reduction to the carrying value of the loan. A loan may be reclassified as accrual if all contractual payments have been received and collection of future principal and interest payments is no longer doubtful.
Fair Value Hedges
Derivatives, Methods of Accounting, Hedging Derivatives	Fair Value Hedges. First Financial utilizes interest rate swaps designated as fair value hedges as a means to offer commercial borrowers products that meet their needs, but are also designed to achieve First Financial’s desired interest rate risk profile. First Financial accomplishes this by entering into swap agreements with commercial borrowers and simultaneously entering into offsetting swap agreements, with substantially matching terms, with institutional counterparties. These interest rate swap agreements generally involve the receipt by First Financial of floating rate amounts from counterparties in exchange for payments to these counterparties by First Financial of fixed rate amounts received from commercial borrowers over the life of the agreements. These interest rate swap agreements do not involve an exchange of the underlying principal or notional amount. This results in First Financial’s loan customers receiving fixed rate funding, while providing First Financial with a floating rate asset. First Financial's matched interest rate swaps economically hedge offsetting "receive fixed" and "pay fixed" exposures, but do not qualify for hedge accounting. The net interest receivable or payable on matched interest rate swaps is accrued and recognized as an adjustment to the interest income of the hedged item. The fair value of matched interest rate swaps is included within Accrued interest and other assets and Accrued interest and other liabilities on the Consolidated Balance Sheets. For the unmatched, pay fixed interest rate swaps, which qualify for hedge accounting, the corresponding fair-value adjustment is included on the Consolidated Balance Sheets in the carrying value of the hedged item. The net interest receivable or payable on unmatched interest rate swaps is accrued and recognized as an adjustment to the interest income of the hedged item. Gains and losses from derivatives not considered effective in hedging the change in fair value of the hedged item, if any, are recognized in income immediately.
Cash Flow Hedges
Derivatives, Methods of Accounting, Hedging Derivatives	Cash Flow Hedges. First Financial utilizes interest rate swaps designated as cash flow hedges to manage the variability of cash flows, primarily net interest income, attributable to changes in interest rates. The net interest receivable or payable on an interest rate swap designated as a cash flow hedge is accrued and recognized as an adjustment to interest income or interest expense while the fair value is included within Accrued interest and other assets or Accrued interest and other liabilities on the Consolidated Balance Sheets. Changes in the fair value of interest rate swaps designated as cash flow hedges are included in accumulated other comprehensive income (loss). Gains and losses from derivatives not considered effective in hedging the cash flows related to the hedged items, if any, are recognized in income immediately.