SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
Sep. 30, 2020
Lessee, Leases [Policy Text Block]	A lease is defined as a contract, or part of a contract, that conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. First Financial is primarily the lessee in its leasing agreements, and substantially all of those agreements are for real estate property for branches, ATM locations or office space.
Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]	Letters of credit are conditional commitments issued by First Financial to guarantee the performance of a client to a third party. First Financial’s letters of credit consist of performance assurances made on behalf of clients who have a contractual commitment to produce or deliver goods or services. The risk to First Financial arises from its obligation to make payment in the event of the client's contractual default to produce the contracted good or service to a third party.
Basis of Presentation Policy	Basis of presentation. The Consolidated Financial Statements of First Financial Bancorp., a financial holding company principally serving Ohio, Indiana, Kentucky and Illinois, include the accounts and operations of First Financial and its wholly-owned subsidiary, First Financial Bank. All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior periods' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings. These interim financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and accompanying notes necessary to constitute a complete set of financial statements required by GAAP and should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Management believes these unaudited consolidated financial statements reflect all adjustments of a normal recurring nature which are necessary for a fair presentation of the results for the interim periods presented. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. The Consolidated Balance Sheet as of December 31, 2019 has been derived from the audited financial statements in the Company’s 2019 Form 10-K.
Use of Estimates, Policy	Use of estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes. These estimates, assumptions and judgments are inherently subjective and may be susceptible to significant change. Actual realized amounts could differ materially from these estimates.
Loans and Leases Receivable, Past Due Status, Policy	Loans are considered past due or delinquent when the contractual principal or interest due in accordance with the terms of the loan agreement remains unpaid after the date of the scheduled payment.
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 90 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. When a loan is classified as nonaccrual, the accrual of interest income is discontinued and previously accrued but unpaid interest is reversed. Any payments received while a loan is on nonaccrual status are applied as a reduction to the carrying value of the loan. A loan classified as nonaccrual may return to accrual status if none of the principal and interest is due and unpaid, and the Bank expects repayment of the remaining contractual principal and interest.
Loans and Leases Receivable, Troubled Debt Restructuring Policy	A loan modification is considered a TDR when the borrower is experiencing financial difficulty and a concession is 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. In accordance with the Coronavirus Aid, Relief, and Economic Security (CARES) Act, performing loans that demonstrated limited signs of credit deterioration, but were modified to provide borrowers relief during the COVID-19 pandemic were not considered to be TDR as of September 30, 2020.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 restructured terms of the loan agreement.
Impaired Financing Receivable, Policy	Loans classified as nonaccrual and loans modified as TDRs are considered nonperforming for September 30, 2020 and impaired as of December 31, 2019.First Financial individually reviews all nonperforming loan relationships greater than $250,000 to determine if an individually evaluated allowance is necessary based on the borrower’s overall financial condition, resources and payment record, support from guarantors and the realizable value of any collateral. Individually evaluated allowances are based on discounted cash flows 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	OREO consists of properties acquired by the Company primarily through the loan foreclosure or repossession process, that results in partial or total satisfaction of problem loans.
Loans and Leases Receivable, Allowance for Loan Losses Policy	Allowance for credit losses - loans and leases. The allowance for credit losses is a valuation account that is deducted from the loans’ amortized cost basis to present the net amount expected to be collected on the loans. Management's determination of the adequacy of the ACL is based on an assessment of the expected credit losses on loan and leases over the expected life of the loan. The ACL is increased by provision expense and decreased by charge-offs, net of recoveries of amounts previously charged-off. Loans are charged off when management believes that the collection of the principal amount owed in full, either through payments from the borrower or a guarantor or from the liquidation of collateral, is unlikely. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Any interest that is accrued but not collected is reversed against interest income when a loan is placed on nonaccrual status, which typically occurs prior to charging off all, or a portion, of a loan. The Company made the policy election to exclude accrued interest receivable on loans and leases from the estimate of credit losses. Management estimates the allowance balance using relevant available information from both internal and external sources, relating to past events, current conditions and reasonable and supportable forecasts. Historical credit loss experience paired with economic forecasts provide the basis for the quantitatively modeled estimation of expected credit losses. First Financial adjusts its quantitative model, as necessary, to reflect conditions not already considered by the quantitative model. These adjustments are commonly known as the Qualitative Framework. First Financial quantitatively models expected credit loss using PD, LGD and EAD over the R&S forecast period, reversion and post-reversion periods. Utilizing third-party software, the Bank forecasts PD by using a parameterized transition matrix approach. Average transition matrices are calculated over the TTC period, which was defined as the period from December 2007 to December 2016. TTC transition matrices are adjusted under forward-looking macroeconomic expectations to obtain R&S forecasts. First Financial is not required to develop forecasts over full the contractual term of the financial asset or group of financial assets. Rather, for periods beyond which the entity is able to make or obtain R&S forecasts of expected credit losses, the Company reverts in a straight line manner over a one year period to an average TTC loss level that is reflective of the prepayment adjusted contractual term of the financial asset or group of financial assets. The R&S period, elected by the bank to be two years, is forecasted using econometric data sourced from Moody's, an industry-leading independent third party. FFB utilizes a non-parametric loss curve approach embedded within a third-party software for estimating LGD. The PD multiplied by LGD produces an expected loss rate that, when calculating the ACL, is applied to contractual loan cash flows, adjusted for expected future rates of principal prepayments. The Company adjusts its quantitative model for certain qualitative factors to reflect the extent to which management expects current conditions and R&S forecasts to differ from the conditions that existed for the period over which historical information was evaluated. The Qualitative Framework reflects changes related to relevant data, such as changes in asset quality trends, portfolio growth and composition, national and local economic factors, credit policy and administration and other factors not considered in the base quantitative model. Loans that do not share risk characteristics are evaluated on an individual basis. First Financial will typically evaluate on an individual basis any loans that are on nonaccrual, designated as a TDR, or reasonably expected to be designated as a TDR. When management determines that foreclosure is probable or when repayment is expected to be provided substantially through the operation or sale of underlying collateral, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs. For loans evaluated on an individual basis that are not determined to be collateral dependent, a discounted cash flow analysis is performed to determine expected credit losses. Expected credit losses are estimated over the contractual term of the loans, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. Credit card receivables do not have stated maturities. In determining the estimated life of a credit card receivable, management first estimates the future cash flows expected to be received and then applies those expected future cash flows to the credit card balance.The allowance for credit losses is a valuation account that is deducted from the loans’ amortized cost basis to present the net amount expected to be collected on the loans. The ACL is increased by provision expense and decreased by 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 a guarantor or from the liquidation of collateral. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Accrued interest receivable on loans and leases, which totaled $41.2 million as of September 30, 2020, is excluded from the estimate of credit losses. Management estimates the allowance balance using relevant available information from both internal and external sources, relating to past events, current conditions and reasonable and supportable forecasts. Historical credit loss experience paired with economic forecasts provides the basis for the quantitatively modeled estimation of expected credit losses. First Financial adjusts its quantitative model, as necessary, to reflect conditions not already considered by the quantitative model. These adjustments are commonly known as the Qualitative Framework. The allowance for credit losses is measured on a collective (pool) basis when similar risk characteristics exist.
Goodwill and Intangible Assets, Goodwill, Policy	Assets and liabilities acquired in a business combination are recorded at their estimated fair values as of the acquisition date. The excess of the purchase price of the acquisition over the fair value of net assets acquired is recorded as goodwill.
Goodwill and Intangible Assets, Goodwill Impairment Policy	Goodwill is evaluated 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	Core deposit intangibles represent the estimated fair value of acquired customer deposit relationships on the date of acquisition and are amortized on an accelerated basis over their estimated useful lives. First Financial's core deposit intangibles have an estimated weighted average remaining life of 7.3 years. First Financial recorded a $39.4 million customer list intangible asset in conjunction with the Bannockburn merger to account for the obligation or advantage on the part of either the Company or the customer to continue the pre-existing relationship subsequent to the merger. The customer list intangible asset is amortized on a straight-line basis over its estimated useful life of 11 years. Other miscellaneous intangibles include purchase commissions, non-compete agreements and trade name intangibles. Other intangible assets are included in Other intangibles in the Consolidated Balance Sheets.
Income Tax, Policy	The unrecognized tax benefits relate to state income tax exposures from taking tax positions where the Company believes it is likely that, upon examination, a state may take a position contrary to the position taken by First Financial.
Commitments and Contingencies, Policy	Allowance for credit losses - unfunded commitments. Effective January 1, 2020, First Financial adopted ASC 326, at which time First Financial estimated expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life consistent with the Company's ACL methodology for loans and leases. Adjustments to the reserve for unfunded commitments are recorded in Provision for credit losses - unfunded commitments in the Consolidated Statements of Income.Prior to the adoption of ASC 326, First Financial maintained its reserve to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. First Financial determined the adequacy of this reserve based upon an evaluation of the unfunded credit facilities, which included consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology at the time. First Financial offers a variety of financial instruments including loan commitments and letters of credit to assist clients in meeting their requirement for liquidity and credit enhancement. GAAP does not require these financial instruments to be recorded in the Consolidated Financial Statements. First Financial utilizes the same credit policies in issuing commitments and conditional obligations as it does for credit instruments recorded on the Consolidated Balance Sheets. First Financial’s exposure to credit loss in the event of non-performance by the counterparty was represented by the contractual amounts of those instruments. Effective January 1, 2020, First Financial adopted ASC 326, at which time First Financial estimated expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life consistent with the Company's ACL methodology for loans and leases. Adjustments to the reserve for unfunded commitments are recorded in Provision for credit losses - unfunded commitments in the Consolidated Statements of Income. First Financial had $14.8 million of ACL for unfunded commitments recorded in Accrued interest and other liabilities on the Consolidated Balance Sheets as of September 30, 2020. Prior to the adoption of ASC 326, First Financial maintained its reserve to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. First Financial determined the adequacy of this reserve based upon an evaluation of the unfunded credit facilities, which included consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology at the time.
Fair Value Measurement, Policy [Policy Text Block]	The fair value framework as disclosed in the 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.
Fair Value of Financial Instruments, Policy	The following methods, assumptions and valuation techniques were used by First Financial to measure different financial assets and liabilities at fair value on a recurring or nonrecurring basis. Investment securities. Investment securities classified as 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 previously described are considered Level 3. First Financial utilizes values provided by third-party pricing vendors to price the investment securities portfolio in accordance with the fair value hierarchy of the Fair Value Topic and reviews the pricing methodologies utilized by the pricing vendors to ensure that the fair value determination is consistent with the applicable accounting guidance. First Financial’s pricing process includes a series of quality assurance activities where prices are compared to recent market conditions, historical prices and other independent pricing services. Further, the Company periodically validates the fair value of a sample of securities in the portfolio by comparing the fair values to prices from other independent sources for the same or similar securities. First Financial analyzes unusual or significant variances, conducts additional research with the pricing vendor, and if necessary, takes appropriate action based on its findings. The results of the quality assurance process are incorporated into the selection of pricing providers by the portfolio manager. 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 and foreign exchange contracts at the reporting date, using primarily observable market inputs such as interest rate yield curves which represents the cost to terminate the swap if First Financial should choose to do so. Additionally, First Financial utilizes an internally-developed model to value the credit risk component of derivative assets and liabilities, which 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. Nonperforming loans. The fair value of nonperforming loans are specifically reviewed for purposes of determining the appropriate amount of impairment to be allocated to the ACL. 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 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 on an outside appraisal, if deemed significant, or the net book value on the applicable borrower financial statements. 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). Nonperforming loans are measured at fair value on a nonrecurring basis. Any fair value adjustments are recorded in the period expected to occur as provision for credit losses on the Consolidated Statements of Income. OREO. Assets acquired through loan foreclosure are recorded at fair value less costs to sell, with any difference between the fair value of the property and the carrying value of the loan recorded as a charge-off. If the fair value is higher than the carrying amount of the loan, the excess is recognized first as a recovery and then as noninterest income. Subsequent changes in value are reported as adjustments to the carrying amount and are recorded in noninterest expense. The carrying value of OREO is not re-measured to fair value on a recurring basis, but is subject to fair value adjustments when the carrying value differs from the fair value, less estimated selling costs. Fair value is based on recent real estate appraisals and is updated at least annually. The Company classifies OREO in level 3 of the fair value hierarchy.
Loan Commitments, Policy [Policy Text Block]	Loan commitments are agreements to extend credit to a client, absent any violation of conditions established in the commitment agreement. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments will expire without being fully drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The amount of collateral obtained, if deemed necessary by First Financial upon extension of credit, is based on management’s credit evaluation of the client. The collateral held varies, but may include securities, real estate, inventory, plant or equipment.
Economic Impact Policy	COVID-19. In the first nine months of 2020, First Financial's operations and financial results were significantly impacted by the COVID-19 pandemic. The spread of COVID-19 has caused significant economic disruption throughout the United States as state and local governments issued stay at home orders and temporarily closed non-essential businesses. The potential financial impact from the pandemic is unknown at this time, however prolonged disruption may adversely impact several industries within the Company's geographic footprint and impair the ability of First Financial's customers to fulfill their contractual obligations to the Company. This could cause First Financial to experience a material adverse effect on business operations, asset valuations, financial condition and results of operations. Material adverse impacts may include all or a combination of valuation impairments on First Financial's intangible assets, investments, loans, mortgage servicing rights or counter-party risk derivatives.
Other Contract-Mortgage
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial enters into IRLCs and forward commitments for the future delivery of mortgage loans to third party investors, which are considered derivatives. When borrowers secure IRLCs with First Financial and the loans are intended to be sold, First Financial will enter into forward commitments for the future delivery of the loans to third party investors in order to hedge against the effect of changes in interest rates impacting IRLCs and loans held for sale.
Credit Risk
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial manages market value credit risk through counterparty credit policies including a review of total derivative notional position to total assets, total credit exposure to total capital and counterparty credit exposure risk.
Foreign Exchange [Member]
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial may enter into foreign exchange derivative contracts for the benefit of commercial customers to hedge their exposure to foreign currency fluctuations. Similar to the hedging of interest rate risk from interest rate derivative contracts, First Financial also enters into foreign exchange contracts with major financial institutions to economically hedge a substantial portion of the exposure from client driven foreign exchange activity. These derivatives are classified as free-standing instruments with the revaluation gain or loss recorded in Foreign exchange income in the Consolidated Statements of Income. The Company has risk limits and internal controls in place to help ensure excessive risk is not being taken in providing this service to customers. These controls include an independent determination of currency volatility and credit equivalent exposure on these contracts, counterparty credit approvals and country limits performed by independent risk management.
Interest Rate Risk [Member]
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	In conjunction with participating interests in commercial loans, First Financial periodically enters into risk participation agreements with counterparties whereby First Financial assumes a portion of the credit exposure associated with an interest rate swap on the participated loan in exchange for a fee. Under these agreements, First Financial will make payments to the counterparty if the loan customer defaults on its obligation to perform under the interest rate swap contract with the counterparty.
Fair Value Hedges
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

9 Months Ended

Sep. 30, 2020

A lease is defined as a contract, or part of a contract, that conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. First Financial is primarily the lessee in its leasing agreements, and substantially all of those agreements are for real estate property for branches, ATM locations or office space.

Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]

Letters of credit are conditional commitments issued by First Financial to guarantee the performance of a client to a third party. First Financial’s letters of credit consist of performance assurances made on behalf of clients who have a contractual commitment to produce or deliver goods or services. The risk to First Financial arises from its obligation to make payment in the event of the client's contractual default to produce the contracted good or service to a third party.

Basis of Presentation Policy

Basis of presentation. The Consolidated Financial Statements of First Financial Bancorp., a financial holding company principally serving Ohio, Indiana, Kentucky and Illinois, include the accounts and operations of First Financial and its wholly-owned subsidiary, First Financial Bank. All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior periods' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings.

These interim financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and accompanying notes necessary to constitute a complete set of financial statements required by GAAP and should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Management believes these unaudited consolidated financial statements reflect all adjustments of a normal recurring nature which are necessary for a fair presentation of the results for the interim periods presented. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. The Consolidated Balance Sheet as of December 31, 2019 has been derived from the audited financial statements in the Company’s 2019 Form 10-K.

Use of Estimates, Policy

Use of estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes. These estimates, assumptions and judgments are inherently subjective and may be susceptible to significant change. Actual realized amounts could differ materially from these estimates.

Loans and Leases Receivable, Past Due Status, Policy

Loans are considered past due or delinquent when the contractual principal or interest due in accordance with the terms of the loan agreement remains unpaid after the date of the scheduled payment.

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 90 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. When a loan is classified as nonaccrual, the accrual of interest income is discontinued and previously accrued but unpaid interest is reversed. Any payments received while a loan is on nonaccrual status are applied as a reduction to the carrying value of the loan. A loan classified as nonaccrual may return to accrual status if none of the principal and interest is due and unpaid, and the Bank expects repayment of the remaining contractual principal and interest.

Loans and Leases Receivable, Troubled Debt Restructuring Policy

A loan modification is considered a TDR when the borrower is experiencing financial difficulty and a concession is 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. In accordance with the Coronavirus Aid, Relief, and Economic Security (CARES) Act, performing loans that demonstrated limited signs of credit deterioration, but were modified to provide borrowers relief during the COVID-19 pandemic were not considered to be TDR as of September 30, 2020.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 restructured terms of the loan agreement.

Impaired Financing Receivable, Policy

Loans classified as nonaccrual and loans modified as TDRs are considered nonperforming for September 30, 2020 and impaired as of December 31, 2019.First Financial individually reviews all nonperforming loan relationships greater than $250,000 to determine if an individually evaluated allowance is necessary based on the borrower’s overall financial condition, resources and payment record, support from guarantors and the realizable value of any collateral. Individually evaluated allowances are based on discounted cash flows 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

OREO consists of properties acquired by the Company primarily through the loan foreclosure or repossession process, that results in partial or total satisfaction of problem loans.

Loans and Leases Receivable, Allowance for Loan Losses Policy

Allowance for credit losses - loans and leases. The allowance for credit losses is a valuation account that is deducted from the loans’ amortized cost basis to present the net amount expected to be collected on the loans. Management's determination of the adequacy of the ACL is based on an assessment of the expected credit losses on loan and leases over the expected life of the loan. The ACL is increased by provision expense and decreased by charge-offs, net of recoveries of amounts previously charged-off. Loans are charged off when management believes that the collection of the principal amount owed in full, either through payments from the borrower or a guarantor or from the liquidation of collateral, is unlikely. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Any interest that is accrued but not collected is reversed against interest income when a loan is placed on nonaccrual status, which typically occurs prior to charging off all, or a portion, of a loan. The Company made the policy election to exclude accrued interest receivable on loans and leases from the estimate of credit losses.

Management estimates the allowance balance using relevant available information from both internal and external sources, relating to past events, current conditions and reasonable and supportable forecasts. Historical credit loss experience paired with economic forecasts provide the basis for the quantitatively modeled estimation of expected credit losses. First Financial adjusts its quantitative model, as necessary, to reflect conditions not already considered by the quantitative model. These adjustments are commonly known as the Qualitative Framework.

First Financial quantitatively models expected credit loss using PD, LGD and EAD over the R&S forecast period, reversion and post-reversion periods.

Utilizing third-party software, the Bank forecasts PD by using a parameterized transition matrix approach. Average transition matrices are calculated over the TTC period, which was defined as the period from December 2007 to December 2016. TTC transition matrices are adjusted under forward-looking macroeconomic expectations to obtain R&S forecasts.

First Financial is not required to develop forecasts over full the contractual term of the financial asset or group of financial assets. Rather, for periods beyond which the entity is able to make or obtain R&S forecasts of expected credit losses, the Company reverts in a straight line manner over a one year period to an average TTC loss level that is reflective of the

prepayment adjusted contractual term of the financial asset or group of financial assets. The R&S period, elected by the bank to be two years, is forecasted using econometric data sourced from Moody's, an industry-leading independent third party.

FFB utilizes a non-parametric loss curve approach embedded within a third-party software for estimating LGD. The PD multiplied by LGD produces an expected loss rate that, when calculating the ACL, is applied to contractual loan cash flows, adjusted for expected future rates of principal prepayments.

The Company adjusts its quantitative model for certain qualitative factors to reflect the extent to which management expects current conditions and R&S forecasts to differ from the conditions that existed for the period over which historical information was evaluated. The Qualitative Framework reflects changes related to relevant data, such as changes in asset quality trends, portfolio growth and composition, national and local economic factors, credit policy and administration and other factors not considered in the base quantitative model.

Loans that do not share risk characteristics are evaluated on an individual basis. First Financial will typically evaluate on an individual basis any loans that are on nonaccrual, designated as a TDR, or reasonably expected to be designated as a TDR. When management determines that foreclosure is probable or when repayment is expected to be provided substantially through the operation or sale of underlying collateral, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs. For loans evaluated on an individual basis that are not determined to be collateral dependent, a discounted cash flow analysis is performed to determine expected credit losses.

Expected credit losses are estimated over the contractual term of the loans, adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. Credit card receivables do not have stated maturities. In determining the estimated life of a credit card receivable, management first estimates the future cash flows expected to be received and then applies those expected future cash flows to the credit card balance.The allowance for credit losses is a valuation account that is deducted from the loans’ amortized cost basis to present the net amount expected to be collected on the loans. The ACL is increased by provision expense and decreased by 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 a guarantor or from the liquidation of collateral. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Accrued interest receivable on loans and leases, which totaled $41.2 million as of September 30, 2020, is excluded from the estimate of credit losses.

Management estimates the allowance balance using relevant available information from both internal and external sources, relating to past events, current conditions and reasonable and supportable forecasts. Historical credit loss experience paired with economic forecasts provides the basis for the quantitatively modeled estimation of expected credit losses. First Financial adjusts its quantitative model, as necessary, to reflect conditions not already considered by the quantitative model. These adjustments are commonly known as the Qualitative Framework.

The allowance for credit losses is measured on a collective (pool) basis when similar risk characteristics exist.

Goodwill and Intangible Assets, Goodwill, Policy

Assets and liabilities acquired in a business combination are recorded at their estimated fair values as of the acquisition date. The excess of the purchase price of the acquisition over the fair value of net assets acquired is recorded as goodwill.

Goodwill and Intangible Assets, Goodwill Impairment Policy

Goodwill is evaluated 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

Core deposit intangibles represent the estimated fair value of acquired customer deposit relationships on the date of acquisition and are amortized on an accelerated basis over their estimated useful lives. First Financial's core deposit intangibles have an estimated weighted average remaining life of 7.3 years.

First Financial recorded a $39.4 million customer list intangible asset in conjunction with the Bannockburn merger to account for the obligation or advantage on the part of either the Company or the customer to continue the pre-existing relationship subsequent to the merger. The customer list intangible asset is amortized on a straight-line basis over its estimated useful life of 11 years.

Other miscellaneous intangibles include purchase commissions, non-compete agreements and trade name intangibles. Other intangible assets are included in Other intangibles in the Consolidated Balance Sheets.

Income Tax, Policy

The unrecognized tax benefits relate to state income tax exposures from taking tax positions where the Company believes it is likely that, upon examination, a state may take a position contrary to the position taken by First Financial.

Commitments and Contingencies, Policy

Allowance for credit losses - unfunded commitments. Effective January 1, 2020, First Financial adopted ASC 326, at which time First Financial estimated expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life consistent with the Company's ACL methodology for loans and leases. Adjustments to the reserve for unfunded commitments are recorded in Provision for credit losses - unfunded commitments in the Consolidated Statements of Income.Prior to the adoption of ASC 326, First Financial maintained its reserve to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. First Financial determined the adequacy of this reserve based upon an evaluation of the unfunded credit facilities, which included consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology at the time.

First Financial offers a variety of financial instruments including loan commitments and letters of credit to assist clients in meeting their requirement for liquidity and credit enhancement. GAAP does not require these financial instruments to be recorded in the Consolidated Financial Statements.

First Financial utilizes the same credit policies in issuing commitments and conditional obligations as it does for credit instruments recorded on the Consolidated Balance Sheets. First Financial’s exposure to credit loss in the event of non-performance by the counterparty was represented by the contractual amounts of those instruments. Effective January 1, 2020, First Financial adopted ASC 326, at which time First Financial estimated expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life consistent with the Company's ACL methodology for loans and leases. Adjustments to the reserve for unfunded commitments are recorded in Provision for credit losses - unfunded commitments in the Consolidated Statements of Income. First Financial had $14.8 million of ACL for unfunded commitments recorded in Accrued interest and other liabilities on the Consolidated Balance Sheets as of September 30, 2020.

Prior to the adoption of ASC 326, First Financial maintained its reserve to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. First Financial determined the adequacy of this reserve based upon an evaluation of the unfunded credit facilities, which included consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology at the time.

Fair Value Measurement, Policy [Policy Text Block]

The fair value framework as disclosed in the 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.

Fair Value of Financial Instruments, Policy

The following methods, assumptions and valuation techniques were used by First Financial to measure different financial assets and liabilities at fair value on a recurring or nonrecurring basis.

Investment securities. Investment securities classified as 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 previously described are considered Level 3.

First Financial utilizes values provided by third-party pricing vendors to price the investment securities portfolio in accordance with the fair value hierarchy of the Fair Value Topic and reviews the pricing methodologies utilized by the pricing vendors to ensure that the fair value determination is consistent with the applicable accounting guidance. First Financial’s pricing process

includes a series of quality assurance activities where prices are compared to recent market conditions, historical prices and other independent pricing services. Further, the Company periodically validates the fair value of a sample of securities in the portfolio by comparing the fair values to prices from other independent sources for the same or similar securities. First Financial analyzes unusual or significant variances, conducts additional research with the pricing vendor, and if necessary, takes appropriate action based on its findings. The results of the quality assurance process are incorporated into the selection of pricing providers by the portfolio manager.

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 and foreign exchange contracts at the reporting date, using primarily observable market inputs such as interest rate yield curves which represents the cost to terminate the swap if First Financial should choose to do so. Additionally, First Financial utilizes an internally-developed model to value the credit risk component of derivative assets and liabilities, which 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.

Nonperforming loans. The fair value of nonperforming loans are specifically reviewed for purposes of determining the appropriate amount of impairment to be allocated to the ACL. 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 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 on an outside appraisal, if deemed significant, or the net book value on the applicable borrower financial statements. 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). Nonperforming loans are measured at fair value on a nonrecurring basis. Any fair value adjustments are recorded in the period expected to occur as provision for credit losses on the Consolidated Statements of Income.

OREO. Assets acquired through loan foreclosure are recorded at fair value less costs to sell, with any difference between the fair value of the property and the carrying value of the loan recorded as a charge-off. If the fair value is higher than the carrying amount of the loan, the excess is recognized first as a recovery and then as noninterest income. Subsequent changes in value are reported as adjustments to the carrying amount and are recorded in noninterest expense. The carrying value of OREO is not re-measured to fair value on a recurring basis, but is subject to fair value adjustments when the carrying value differs from the fair value, less estimated selling costs. Fair value is based on recent real estate appraisals and is updated at least annually. The Company classifies OREO in level 3 of the fair value hierarchy.

Loan Commitments, Policy [Policy Text Block]

Loan commitments are agreements to extend credit to a client, absent any violation of conditions established in the commitment agreement. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments will expire without being fully drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The amount of collateral obtained, if deemed necessary by First Financial upon extension of credit, is based on management’s credit evaluation of the client. The collateral held varies, but may include securities, real estate, inventory, plant or equipment.

Economic Impact Policy

COVID-19. In the first nine months of 2020, First Financial's operations and financial results were significantly impacted by the COVID-19 pandemic. The spread of COVID-19 has caused significant economic disruption throughout the United States as state and local governments issued stay at home orders and temporarily closed non-essential businesses. The potential financial impact from the pandemic is unknown at this time, however prolonged disruption may adversely impact several industries within the Company's geographic footprint and impair the ability of First Financial's customers to fulfill their contractual obligations to the Company. This could cause First Financial to experience a material adverse effect on business operations, asset valuations, financial condition and results of operations. Material adverse impacts may include all or a combination of valuation impairments on First Financial's intangible assets, investments, loans, mortgage servicing rights or counter-party risk derivatives.

Other Contract-Mortgage

Derivatives, Methods of Accounting, Hedging Derivatives, Policy

First Financial enters into IRLCs and forward commitments for the future delivery of mortgage loans to third party investors, which are considered derivatives. When borrowers secure IRLCs with First Financial and the loans are intended to be sold, First Financial will enter into forward commitments for the future delivery of the loans to third party investors in order to hedge against the effect of changes in interest rates impacting IRLCs and loans held for sale.

Credit Risk

Derivatives, Methods of Accounting, Hedging Derivatives, Policy

First Financial manages market value credit risk through counterparty credit policies including a review of total derivative notional position to total assets, total credit exposure to total capital and counterparty credit exposure risk.

Foreign Exchange [Member]

Derivatives, Methods of Accounting, Hedging Derivatives, Policy

First Financial may enter into foreign exchange derivative contracts for the benefit of commercial customers to hedge their exposure to foreign currency fluctuations. Similar to the hedging of interest rate risk from interest rate derivative contracts, First Financial also enters into foreign exchange contracts with major financial institutions to economically hedge a substantial portion of the exposure from client driven foreign exchange activity. These derivatives are classified as free-standing instruments with the revaluation gain or loss recorded in Foreign exchange income in the Consolidated Statements of Income. The Company has risk limits and internal controls in place to help ensure excessive risk is not being taken in providing this service to customers. These controls include an independent determination of currency volatility and credit equivalent exposure on these contracts, counterparty credit approvals and country limits performed by independent risk management.

Interest Rate Risk [Member]

Derivatives, Methods of Accounting, Hedging Derivatives, Policy

In conjunction with participating interests in commercial loans, First Financial periodically enters into risk participation agreements with counterparties whereby First Financial assumes a portion of the credit exposure associated with an interest rate swap on the participated loan in exchange for a fee. Under these agreements, First Financial will make payments to the counterparty if the loan customer defaults on its obligation to perform under the interest rate swap contract with the counterparty.

Fair Value Hedges

Derivatives, Methods of Accounting, Hedging Derivatives, Policy

First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets