First Financial Bancorp. (FFBC) 10-K 26 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 23, 2018
DOCUMENT AND ENTITY INFORMATION [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	FFBC
Entity Registrant Name	FIRST FINANCIAL BANCORP /OH/
Entity Central Index Key	708,955
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,093,120
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float	$ 1,690,000,000

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and due from banks	$ 150,650,000	$ 121,598,000
Interest-bearing deposits with other banks	33,974,000	82,450,000
Investment securities available-for-sale, at fair value (amortized cost $1,348,227 at December 31, 2017 and $1,045,337 at December 31, 2016)	1,349,408,000	1,039,870,000
Investment securities held-to-maturity (fair value $653,101 at December 31, 2017 and $763,575 at December 31, 2016)	654,008,000	763,254,000
Other investments	53,140,000	51,077,000
Loans held for sale	11,502,000	13,135,000
Loans and leases
Commercial and industrial	1,912,743,000	1,781,948,000
Lease financing	89,347,000	93,108,000
Construction real estate	467,730,000	399,434,000
Commercial real estate	2,490,091,000	2,427,577,000
Residential real estate	471,391,000	500,980,000
Home equity	493,604,000	460,388,000
Installment	41,586,000	50,639,000
Credit card	46,691,000	43,408,000
Total loans and leases	6,013,183,000	5,757,482,000
Less: Allowance for loan and lease losses	54,021,000	57,961,000
Net loans and leases	5,959,162,000	5,699,521,000
Premises and equipment	125,036,000	131,579,000
Goodwill and other intangibles	209,379,000	210,625,000
Accrued interest and other assets	350,664,000	324,858,000
Total assets	8,896,923,000	8,437,967,000
Deposits
Interest-bearing demand	1,453,463,000	1,513,771,000
Savings	2,462,420,000	2,142,189,000
Time	1,317,105,000	1,321,843,000
Total interest-bearing deposits	5,232,988,000	4,977,803,000
Noninterest-bearing	1,662,058,000	1,547,985,000
Total deposits	6,895,046,000	6,525,788,000
Federal funds purchased and securities sold under agreements to repurchase	72,265,000	120,212,000
Federal Home Loan Bank short-term borrowings	742,300,000	687,700,000
Total short-term borrowings	814,565,000	807,912,000
Long-term debt	119,654,000	119,589,000
Total borrowed funds	934,219,000	927,501,000
Accrued interest and other liabilities	136,994,000	119,454,000
Total liabilities	7,966,259,000	7,572,743,000
Shareholders' equity
Common stock - no par value	573,109,000	570,382,000
Retained earnings	491,847,000	437,188,000
Accumulated other comprehensive income (loss)	(20,390,000)	(28,443,000)
Treasury stock, at cost, 6,661,644 shares in 2017 and 6,751,179 shares in 2016	(113,902,000)	(113,903,000)
Total shareholders' equity	930,664,000	865,224,000
Total liabilities and shareholders’ equity	$ 8,896,923,000	$ 8,437,967,000

CONSOLIDATED BALANCE SHEETS CON

CONSOLIDATED BALANCE SHEETS CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Investment securities available-for-sale, cost	$ 1,348,227	$ 1,045,337
Investment securities held-to-maturity, market value	$ 653,101	$ 763,575
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	160,000,000	160,000,000
Common Stock, Shares, Issued	68,730,731	68,730,731
Treasury Stock, Shares	6,661,644	6,751,179

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Loans, including fees	$ 280,111	$ 262,703	$ 230,246
Investment securities
Taxable	50,568	43,103	39,577
Tax-exempt	5,918	4,535	4,611
Total investment securities interest	56,486	47,638	44,188
Other earning assets	(3,524)	(4,391)	(4,675)
Total interest income	333,073	305,950	269,759
Interest expense
Deposits	35,182	22,613	19,474
Short-term borrowings	8,193	4,506	1,364
Long-term borrowings	6,153	6,160	2,419
Total interest expense	49,528	33,279	23,257
Net interest income	283,545	272,671	246,502
Provision for loan and lease losses	3,582	10,140	9,641
Net interest income after provision for loan and lease losses	279,963	262,531	236,861
Noninterest income
Service charges on deposit accounts	19,775	18,933	19,015
Trust and wealth management fees	14,073	13,200	13,128
Bankcard income	13,298	12,132	11,578
Client derivative fees	6,418	4,570	4,389
Net gains on sales of loans	5,169	6,804	6,471
Net gains (losses) on sales of investment securities	1,649	234	1,505
Other	15,760	13,728	19,116
Total noninterest income	76,142	69,601	75,202
Noninterest expenses
Salaries and employee benefits	132,560	122,361	111,792
Net occupancy	17,397	18,329	18,232
Furniture and equipment	8,443	8,663	8,722
Data processing	14,022	11,406	10,863
Marketing	3,201	3,965	3,723
Communication	1,819	1,889	2,161
Professional services	15,023	6,303	9,622
State intangible tax	2,655	2,034	2,331
FDIC assessments	3,944	4,293	4,446
Loss (gain) - other real estate owned	642	(1,212)	1,861
Other	40,236	23,370	27,377
Total noninterest expenses	239,942	201,401	201,130
Income before income taxes	116,163	130,731	110,933
Income tax expense	19,376	42,205	35,870
Net income	$ 96,787	$ 88,526	$ 75,063
Earnings per common share
Basic	$ 1.57	$ 1.45	$ 1.23
Diluted	$ 1.56	$ 1.43	$ 1.21
Average common shares outstanding - basic	61,529,460	61,206,093	61,062,657
Average common shares outstanding - diluted	62,171,590	61,985,422	61,847,547

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 96,787	$ 88,526	$ 75,063
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on investment securities arising during the period	4,367	384	(2,427)
Change in retirement obligation	3,172	1,245	(6,144)
Unrealized gain (loss) on derivatives	514	508	(650)
Unrealized gain (loss) on foreign currency exchange	0	0	50
Other comprehensive income (loss)	8,053	2,137	(9,171)
Comprehensive income	$ 104,840	$ 90,663	$ 65,892

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Balances at January 1, 2014 at Dec. 31, 2014	$ 784,077	$ 574,643	$ 352,893	$ (21,409)	$ (122,050)
Balances at January 1, 2014 at Dec. 31, 2014		68,730,731			(7,274,184)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	75,063		75,063
Other comprehensive loss	(9,171)			(9,171)
Cash dividends declared:
Common stock at $0.64 per share in 2016, $0.64 per share in 2015, and $0.61 per share in 2014	$ (39,410)		(39,410)
Treasury Stock, Shares, Acquired	(239,967)				(239,967)
Treasury Stock, Value, Acquired, Cost Method	$ (4,498)				$ (4,498)
Adjustments to Additional Paid in Capital, Other	13	$ (975)			$ 988
Stock Issued During Period, Shares, Other					58,812
Excess tax benefit on share-based compensation	146	146
Exercise of stock options, net of shares purchased (in shares)					62,261
Exercise of stock options, net of shares purchased	679	(367)			$ 1,046
Restricted stock awards, net of forfeitures (in shares)					304,027
Restricted stock awards, net of forfeitures	(1,266)	(6,341)			$ 5,075
Share-based compensation expense	4,049	$ 4,049
Ending Balances (in shares) at Dec. 31, 2015		68,730,731			(7,089,051)
Ending Balances at Dec. 31, 2015	809,376	$ 571,155	388,240	(30,580)	$ (119,439)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment for accounting changes FASB ASU 2014-01 adjustment	(306)		(306)
Net income	88,526		88,526
Other comprehensive loss	2,137			2,137
Cash dividends declared:
Common stock at $0.64 per share in 2016, $0.64 per share in 2015, and $0.61 per share in 2014	$ (39,578)		(39,578)
Treasury Stock, Shares, Acquired	0
Adjustments to Additional Paid in Capital, Other	$ 0	(1,507)			$ 1,507
Stock Issued During Period, Shares, Other					89,383
Excess tax benefit on share-based compensation	264	264
Exercise of stock options, net of shares purchased (in shares)					65,515
Exercise of stock options, net of shares purchased	726	(379)			$ 1,105
Restricted stock awards, net of forfeitures (in shares)					182,974
Restricted stock awards, net of forfeitures	(1,581)	(4,505)			$ 2,924
Share-based compensation expense	5,354	$ 5,354
Ending Balances (in shares) at Dec. 31, 2016		68,730,731			(6,751,179)
Ending Balances at Dec. 31, 2016	865,224	$ 570,382	437,188	(28,443)	$ (113,903)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	96,787		96,787
Other comprehensive loss	8,053			8,053
Cash dividends declared:
Common stock at $0.64 per share in 2016, $0.64 per share in 2015, and $0.61 per share in 2014	$ (42,128)		(42,128)
Treasury Stock, Shares, Acquired	0
Adjustments to Additional Paid in Capital, Other	$ 0	(99)			$ 99
Stock Issued During Period, Shares, Other					5,843
Exercise of stock options, net of shares purchased (in shares)	101,507				58,212
Exercise of stock options, net of shares purchased	$ 75	(912)			$ 987
Restricted stock awards, net of forfeitures (in shares)					25,480
Restricted stock awards, net of forfeitures	(2,793)	(1,708)			$ (1,085)
Share-based compensation expense	5,446	$ 5,446
Ending Balances (in shares) at Dec. 31, 2017		68,730,731			(6,661,644)
Ending Balances at Dec. 31, 2017	$ 930,664	$ 573,109	$ 491,847	$ (20,390)	$ (113,902)

CONSOLIDATED STATEMENTS OF CHA7

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock, Dividends, Per Share, Declared	$ 0.68	$ 0.64	$ 0.64

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 96,787	$ 88,526	$ 75,063
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan and lease losses	3,582	10,140	9,641
Depreciation and amortization	12,645	13,037	13,266
Stock-based compensation expense	5,446	5,354	4,049
Pension expense (income)	(628)	(1,153)	(1,042)
Net amortization (accretion) on investment securities	10,798	8,476	7,899
Net (gains) losses on sales of investments securities	(1,649)	(234)	(1,505)
Originations of loans held for sale	(157,796)	(232,526)	(246,845)
Net (gains) losses on sales of loans held for sale	(5,169)	(6,804)	(6,471)
Proceeds from sales of loans held for sale	163,300	246,829	242,029
Deferred income taxes	(4,488)	346	4,192
Decrease (increase) cash surrender value of life insurance	(3,792)	(186)	(5,379)
Decrease (increase) in interest receivable	(5,707)	(1,456)	(995)
Decrease in indemnification asset	(10,117)	(5,613)	(5,036)
(Decrease) increase in interest payable	55	46	2,296
Decrease (increase) in other assets	(23,808)	(5,347)	(33,370)
(Decrease) increase in other liabilities	21,478	7,700	23,703
Net cash provided by (used in) operating activities	121,171	138,361	91,567
Investing activities
Proceeds from sales of investment securities available-for-sale	189,962	206,990	70,219
Proceeds from calls, paydowns and maturities of securities available-for-sale	224,690	186,132	120,953
Purchases of securities available-for-sale	(723,131)	(396,984)	(547,901)
Proceeds from Sale of Held-to-maturity Securities	0	4,862	0
Proceeds from calls, paydowns and maturities of securities held-to-maturity	121,903	127,021	140,059
Purchases of securities held-to-maturity	(23,402)	(11,196)	(3,520)
Net decrease (increase) in interest-bearing deposits with other banks	48,476	(48,716)	(11,104)
Net decrease (increase) in loans and leases	(266,043)	(376,848)	(390,312)
Proceeds from disposal of other real estate owned	6,983	9,356	15,817
Purchases of premises and equipment	(6,537)	(9,726)	(7,467)
Net cash (paid) acquired from business combinations	0	0	(305,591)
Net cash provided by (used in) investing activities	(427,099)	(309,109)	(918,847)
Financing activities
Net (decrease) increase in total deposits	369,258	346,164	523,882
Net (decrease) increase in short-term borrowings	6,653	(130,513)	277,033
Payments on long-term borrowings	(94)	(86)	(46,238)
Proceeds from Issuance of Subordinated Long-term Debt	0	0	120,000
Cash dividends paid on common stock	(41,178)	(39,125)	(39,070)
Treasury stock purchase	0	0	(4,498)
Proceeds from exercise of stock options	341	801	744
Excess tax benefit on share-based compensation	0	264	146
Net cash provided by (used in) financing activities	334,980	177,505	831,999
Cash and due from banks
Net (decrease) increase in Cash and due from banks	29,052	6,757	4,719
Cash and due from banks at beginning of year	121,598	114,841	110,122
Cash and due from banks at end of year	150,650	121,598	114,841
Supplemental disclosures
Interest paid	49,474	33,233	20,961
Income taxes paid	38,329	37,566	31,193
Acquisition of other real estate owned through foreclosure	4,119	2,872	8,398
Issuance of restricted stock awards	$ 6,416	$ 5,759	$ 7,760

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
BASIS OF PRESENTATION	Summary of Significant Accounting Policies Basis of presentation. The Consolidated Financial Statements of First Financial Bancorp., 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. All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior years' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings. Use of estimates. The preparation of Consolidated 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. Actual realized amounts could differ materially from those estimates. Cash and due from banks. Cash and due from banks consist of currency, coin and cash items due from banks. Cash items due from banks include noninterest bearing deposits held at other banks. Investment securities. First Financial classifies debt and equity securities into three categories: held-to-maturity, trading and available-for-sale. Management classifies investment securities into the appropriate category at the time of purchase and re-evaluates that classification as deemed appropriate. Investment securities are classified as held-to-maturity when First Financial has the positive intent and ability to hold the securities to maturity. Held-to-maturity securities are recorded at amortized cost. Investment securities classified as trading are held principally for resale in the near-term and are recorded at fair value. Fair value is determined using quoted market prices. Gains or losses on trading securities, both realized and unrealized, are reported in noninterest income. Investment securities not classified as either held-to-maturity or trading are classified as available-for-sale. Available-for-sale securities are recorded at fair value, with the unrealized gains and losses, net of tax, reported as a separate component of accumulated other comprehensive income (loss) in shareholders' equity. The amortized cost of investment securities classified as either held-to-maturity or available-for-sale is adjusted for amortization of premiums and accretion of discounts to maturity, or in the case of mortgage-backed securities, over the estimated life of the security. Such amortization and accretion are considered an adjustment to the yield on the security and included in interest income from investments. Interest and dividends are included in interest income from investment securities in the Consolidated Statements of Income. Realized gains and losses are based on the amortized cost of the security sold using the specific identification method. Available-for-sale and held-to-maturity securities are reviewed quarterly for potential impairment. In performing this review, management considers the length of time and extent to which the fair value of the security has been less than amortized cost, the financial condition and near-term prospects of the issuer and the ability and intent of First Financial to hold the security for a period sufficient to allow for any anticipated recovery in fair value. If the fair value of a security is less than the amortized cost and the impairment is determined to be other-than-temporary, the security is written down, establishing a new and reduced cost basis. The related charge is recorded in the Consolidated Statements of Income. Other investments. Other investments include holdings in FRB stock and FHLB stock, which are both carried at cost. Loans held for sale. Loans held for sale consists of residential real estate loans newly originated for the purpose of sale to third parties, and in certain circumstances, loans previously originated that have been specifically identified by management for sale based on predetermined criteria. Loans transferred to held for sale status are carried at the lower of cost or fair value. Any subsequent change in the carrying value of transferred loans, not to exceed original cost, is recorded in the Consolidated Statements of Income. The Bank sells loans with servicing retained or released depending on pricing and market conditions. Loans and leases, excluding purchased impaired loans. Loans and leases for which First Financial has the intent and ability to hold for the foreseeable future, or until maturity or payoff, are classified in the Consolidated Balance Sheets as loans and leases. Loans and leases are carried at the principal amount outstanding, net of unamortized deferred loan origination fees and costs, and net of unearned income, with the exception of loans subject to fair value requirements. Loan origination and commitment fees received, as well as certain direct loan origination costs paid, are deferred, and the net amount is amortized as an adjustment to the related loan's yield. Interest income on loans and leases is recorded on an accrual basis. 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 classified as nonaccrual are applied as a reduction to the carrying value of the loan. A loan may return to accrual status if collection of future principal and interest payments is no longer doubtful. Acquired loans. Acquired loans are recorded at their estimated fair value at the time of acquisition. Estimated fair values for acquired loans are based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, interest rate, term of loan, whether or not the loan was amortizing and a discount rate reflecting the Company's assessment of risk inherent in the cash flow estimates. Acquired loans are grouped together according to similar characteristics and treated in the aggregate when applying various valuation techniques. First Financial evaluates acquired loans for impairment in accordance with the provisions of FASB ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality. Acquired loans with evidence of credit deterioration since origination are accounted for under FASB ASC Topic 310-30 and are referred to as purchased impaired loans. 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 purchased impaired loans. Acquired loans outside of the scope of FASB ASC Topic 310-30 are accounted for under FASB ASC Topic 310-20, Receivables-Nonrefundable Fees and Costs. Discounts created when the loans were recorded at their estimated fair values at acquisition are amortized over the remaining term of the loan as an adjustment to the related loan's yield. The accrual of interest income is discontinued when the collection of a loan or interest, in whole or in part, is doubtful. Certain loans acquired in FDIC-assisted transactions were initially covered under loss sharing agreements and are referred to as covered loans during the indemnification period. Subsequent to the indemnification period, they are referred to as formerly covered loans. Allowance for loan and lease losses. For each reporting period, management maintains the ALLL at a level that it considers sufficient to absorb probable incurred loan and lease losses inherent in the portfolio. Management determines the adequacy of the ALLL 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. Management's determination of the adequacy of the ALLL is based on an assessment of the probable incurred loan and lease losses inherent in the portfolio given the conditions at the time. The ALLL 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 from the liquidation of collateral. Commercial loan and lease relationships (including time and demand notes, tax-exempt loans, C&I, construction, commercial real estate, mezzanine loans and lease financing) greater than $250,000 that are considered impaired, or designated as a TDR, are evaluated to determine the need for a specific allowance based on the borrower's overall financial condition, resources, payment record, guarantor support and the realizable value of any collateral. The allowance for non-impaired commercial loans and leases, as well as impaired commercial loan and lease relationships less than $250,000 , includes a process of estimating the probable losses incurred in the portfolio by loan type, based on First Financial's internal system of credit risk ratings and historical loss data. These estimates may also be adjusted based upon trends in the values of the underlying collateral, delinquent and nonaccrual loans, prevailing economic conditions and changes in lending strategies, among other influencing factors. Consumer loans are generally evaluated by loan type, 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 probable losses incurred 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 greater than $250,000 classified as TDRs are individually evaluated to determine an appropriate allowance. For purchased impaired loans, expected cash flows are re-estimated periodically with declines in gross expected cash flows recorded as provision expense during the period. The related, estimated reimbursement for loan losses due from the FDIC under loss sharing agreements, if applicable, is recorded as FDIC loss sharing income. Reserve for unfunded commitments . First Financial maintains a reserve that it considers sufficient to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. This reserve is included in Accrued interest and other liabilities on the Consolidated Balance Sheets, First Financial determines the adequacy of the reserve based upon an evaluation of the unfunded credit facilities, which includes consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology. Adjustments to the reserve for unfunded commitments are included in Other noninterest expense in the Consolidated Statements of Income. FDIC indemnification asset. The FDIC indemnification asset results from the loss sharing agreements entered into in conjunction with First Financial's FDIC-assisted transactions, and represents expected reimbursements from the FDIC for losses on covered assets. The FDIC indemnification asset is measured separately from the related assets covered by loss sharing agreements with the FDIC as it is not contractually embedded in those assets and is not transferable should First Financial choose to dispose of the covered assets. Pursuant to the terms of the loss sharing agreements, covered assets are subject to stated loss thresholds whereby the FDIC will reimburse First Financial for 80% of losses up to the stated loss thresholds, and 95% of losses in excess of the thresholds. The FDIC indemnification asset was recorded at its estimated fair value at the time of the FDIC-assisted transactions. Fair values were estimated using projected cash flows related to the loss sharing agreements based on the expected reimbursements for losses and the applicable loss sharing percentages. These cash flows were discounted to reflect the uncertainty of the timing of the loss sharing reimbursement from the FDIC. The accounting for the FDIC indemnification asset is closely related to the accounting for the underlying, indemnified assets as well as ongoing assessment of the collectibility of the indemnification asset. The primary activities impacting the FDIC indemnification asset are FDIC claims, amortization, FDIC loss sharing income and accelerated discount. In December 2017, First Financial entered into a preliminary agreement with the FDIC to early terminate the FDIC loss sharing agreements. See Note 5 for further discussion of the indemnification asset and the preliminary agreement to terminate the FDIC loss sharing agreements. Premises and equipment. Premises and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are principally computed on the straight-line method over the estimated useful lives of the assets. Useful lives generally range from 10 to 40 years for building and building improvements; 3 to 10 years for furniture, fixtures and equipment; and 3 to 5 years for software, hardware and data handling equipment. Land improvements are depreciated over 20 years and leasehold improvements are depreciated over the lesser of the term of the respective lease or the useful life of the asset. Premises and equipment are evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Maintenance and repairs are expensed as incurred. Goodwill and other indefinite lived intangible assets. Under accounting for business combinations, the net assets of entities acquired by First Financial are recorded at their estimated fair value at the date of acquisition. The excess cost of the acquisition over the fair value of net assets acquired is recorded as goodwill. Goodwill and intangible assets deemed to have indefinite lives, if any, are not amortized, but are subject to annual impairment tests. The Company is required to evaluate goodwill for impairment on an annual basis or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. First Financial performs its annual impairment test effective October 1, absent events or changes in circumstances that indicate the carrying value of goodwill may not be recoverable. The Company’s goodwill is accounted for in a single reporting unit representing the consolidated entity. Fair value is estimated using the market capitalization of the Company as of the annual impairment testing date. First Financial also utilizes additional information and analyses to corroborate the use of the Company’s market capitalization as a proper indicator of fair value for purposes of the annual goodwill impairment test. Core deposit intangibles. CDI represent the estimated value of acquired customer deposit relationships. CDI are recorded at fair value at the date of acquisition and are based on a discounted cash flow methodology that gives appropriate consideration to expected customer attrition rates, cost of the deposit base, reserve requirements and the net maintenance cost attributable to customer deposits. Core deposit intangibles are amortized on an accelerated basis over their estimated useful lives. Other real estate owned. OREO consists of properties acquired by the Company primarily through the loan foreclosure or repossession process, or other resolution activity that results in partial or total satisfaction of problem loans. OREO properties are recorded at fair value, less estimated disposal costs (net realizable value). Losses arising at the time of acquisition of such properties are charged against the ALLL. Management performs periodic valuations to assess the adequacy of recorded OREO balances and subsequent write-downs in the carrying value of OREO properties are expensed as incurred. Improvements to OREO 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. When management disposes of an OREO property, any gains or losses realized at the time of disposal are reflected in the Consolidated Statements of Income. Affordable housing projects. First Financial has investment in certain qualified affordable housing projects. These projects are indirect federal subsidies that provide tax incentives to encourage investment in the development, acquisition and rehabilitation of affordable rental housing, and allow investors to claim tax credits and other tax benefits (such as deductions from taxable income for operating losses) on their federal income tax returns. The principal risk associated with qualified affordable housing investments is the potential for noncompliance with the tax code requirements, such as, failure to rent properties to qualified tenants, resulting in unavailability or recapture of the tax credits and other tax benefits. Investments in affordable housing projects are accounted for under the proportional amortization method and are included in Accrued interest and other assets in the Consolidated Balance Sheets. Investments in historic tax credits. First Financial has noncontrolling financial investments in private investment funds and partnerships which are not consolidated. These investments may generate a return through the realization of federal and state income tax credits, as well as other tax benefits, such as tax deductions from net operating losses of the investments over a period of time. Investments in historic tax credits are accounted for under the equity method of accounting. The Company’s recorded investment in these entities is carried in Accrued interest and other assets on the Consolidated Balance Sheets. Income taxes. First Financial and its subsidiaries file a consolidated federal income tax return. Each subsidiary provides for income taxes on a separate return basis, and remits to First Financial amounts determined to be currently payable. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Interest and penalties on income tax assessments or income tax refunds are recognized as a component of noninterest expense in the Consolidated Statements of Income. Pension. First Financial sponsors a non-contributory defined benefit pension plan covering substantially all employees. The measurement of the accrued benefit liability and the annual pension expense involves actuarial and economic assumptions, which include the discount rate, the expected return on plan assets and the rate of compensation increase. Derivative instruments. First Financial accounts for its derivative financial instruments in accordance with FASB ASC Topic 815, Derivatives and Hedging. FASB ASC Topic 815 requires all derivative instruments to be carried at fair value on the balance sheet. The accounting for changes in the fair value of derivatives is based on the intended use of the derivative and the resulting designation. Derivatives used to hedge the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives used to hedge the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Client derivatives - First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets. Upon entering into an interest rate swap with a borrower, the Bank simultaneously enters into an offsetting swap agreement with an institutional counterparty, with substantially matching terms. These matched interest rate swap agreements generally involve the receipt by First Financial of floating rate amounts from the 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. First Financial's matched interest rate swaps qualify as derivatives, but are not designated as hedging instruments. The net interest receivable or payable on matched interest rate swaps is accrued and recognized as an adjustment to interest income. The fair values of back to back swaps are included within Accrued interest and other assets and Accrued interest and other liabilities on the Consolidated Balance Sheets. Credit derivatives - 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. The fair value of these agreements is recorded on the Consolidated Balance Sheets in Accrued interest and other liabilities. Mortgage derivatives - 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 an IRLC with First Financial and the loan is 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 and Loans held for sale. The fair value of these agreements is recorded on the Consolidated Balance Sheets in Accrued interest and other assets. Stock-based compensation. First Financial grants stock-based awards, including restricted stock awards and options to purchase the Company’s common stock. Stock option grants are for a fixed number of shares to employees and directors with an exercise price equal to the fair value of the shares at the date of grant. Stock-based compensation expense is recognized in the Consolidated Statements of Income on a straight-line basis over the vesting period. As compensation expense is recognized, a deferred tax asset is recorded that represents an estimate of the future tax deduction from exercise. At the time stock-based awards are exercised, canceled or expire, First Financial may be required to recognize an adjustment to tax expense. Earnings per share. Basic earnings per common share is computed by dividing net income available to common shareholders by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding, unvested shares and dilutive common stock equivalents outstanding during the period. Common stock equivalents, which consist of common stock issuable under the assumed exercise of stock options granted under First Financial's stock-based compensation plans and the assumed conversion of common stock warrants, are calculated using the treasury stock method. Segments and related information. While the Company monitors the operating results of its four lines of business, operations are managed and financial performance is evaluated on a consolidated basis. Accordingly, and consistent with prior years, all of the Company's operations are considered by management to be aggregated in one reportable operating segment.

RECENTLY ADOPTED AND ISSUED ACC

RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS	Recently Adopted and Issued Accounting Standards In May 2014, the FASB issued an update (ASU 2014-09, Revenue from Contracts with Customers) which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. Under the revised standard, an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The ASU applies to all contracts with customers except those that are within the scope of other topics in the FASB Accounting Standards Codification. Certain of the ASU’s provisions also apply to transfers of nonfinancial assets, including in-substance nonfinancial assets that are not an output of an entity’s ordinary activities, such as sales of property, plant, and equipment; real estate; or intangible assets. The ASU also requires significantly expanded disclosures about revenue recognition. The provisions of ASU 2014-09 become effective for interim and annual reporting periods beginning after December 15, 2017. The amended guidance does not apply to revenue associated with financial instruments, including loans and securities. As such management has evaluated revenue streams within noninterest income, specifically service charges on deposits and trust and wealth management fees, to assess applicability of this guidance, and anticipates adopting the amended guidance using a modified retrospective approach in the first quarter of 2018. First Financial does not anticipate that this update will impact Income before taxes or net income, however additional disclosures will be required upon adoption. In January 2016, the FASB issued an update (ASU 2016-01, Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities) which requires entities to measure many equity investments at fair value and recognize changes in fair value in net income. This update does not apply to equity investments that result in consolidation, those accounted for under the equity method and certain others, and will eliminate use of the available for sale classification for equity securities while providing a new measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient. The guidance in this ASU will become effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted. First Financial does not anticipate this update will have a material impact on its Consolidated Financial Statements. In February 2016, the FASB issued an update (ASU 2016-02, Leases) which requires lessees to record most leases on their balance sheet and recognize leasing expenses in the income statement. Operating leases, except for short-term leases that are subject to an accounting policy election, will be recorded on the balance sheet for lessees by establishing a lease liability and corresponding right-of-use asset. The guidance in this ASU will become effective for interim and annual reporting periods beginning after December 15, 2018, with early adoption permitted. Given operating leases outstanding as of December 31, 2017, First Financial does not expect this ASU to have a material impact on the income statement, but does anticipate an increase in the Company's assets and liabilities. Decisions to repurchase, modify or renew leases prior to the implementation date will impact this level of materiality. In March 2016, the FASB issued an update (ASU 2016-05, Derivatives and Hedging: Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships) which clarifies that the novation of a derivative contract in a hedge accounting relationship does not, in and of itself, require de-designation of that hedge accounting relationship. In the event of a novation, hedge accounting relationships could continue if all other hedge accounting criteria are met, including the expectation that the hedge will be highly effective when the creditworthiness of the new counterparty to the derivative contract is considered. The guidance in this ASU became effective in the first quarter of 2017 and did not have a material impact on the Consolidated Financial Statements. In March 2016, the FASB issued an update (ASU 2016-06, Derivatives and Hedging: Contingent Put and Call Options in Debt Instruments) which clarifies that an assessment of whether an embedded contingent put or call option is clearly and closely related to the debt host requires only an analysis of the four-step decision sequence in FASB Topic ASC Topic 815, Derivatives and Hedging. Entities are required to apply the guidance to existing debt instruments (or hybrid financial instruments that are determined to have a debt host) using a modified retrospective transition method as of the period of adoption. The guidance in this ASU became effective in the first quarter of 2017 and did not have a material impact on the Consolidated Financial Statements. In March 2016, the FASB issued an update (ASU 2016-07, Investments-Equity Method and Joint Ventures: Simplifying the Transition to the Equity Method of Accounting) which eliminates the requirement to retrospectively apply the equity method when an investment that had been accounted for utilizing another method qualifies for use of the equity method. The guidance in this ASU became effective in the first quarter of 2017 and did not have a material impact on the Consolidated Financial Statements. In March 2016, the FASB issued an update (ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting) which requires recognition of the income tax effects of share-based awards in the income statement when the awards vest or are settled (i.e., Additional Paid-in-Capital pools will be eliminated). The guidance in this ASU became effective in the first quarter of 2017. Adoption of this guidance resulted in a $1.6 million reduction in income tax expense during 2017. In June 2016, the FASB issued an update (ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments) which significantly changes how entities are required to measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. This update will replace the current incurred loss approach for estimating credit losses with an expected loss model for instruments measured at amortized cost, including loans and leases. Expected credit losses are required to be based on amortized cost and reflect losses expected over the remaining contractual life of the asset. Management is expected to consider any available information relevant to assessing the collectibility of contractual cash flows, such as information about past events, current conditions, voluntary prepayments and reasonable and supportable forecasts, when developing expected credit loss estimates. In addition to the new framework for calculating the ALLL, this update requires allowances for available-for-sale debt securities rather than a reduction of the security's carrying amount under the current other-than-temporary impairment model. This update also simplifies the accounting model for purchased credit-impaired debt securities and loans and will require new and updated footnote disclosures. The guidance in this ASU will become effective for interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted for all entities for interim and annual reporting periods beginning after December 15, 2018. First Financial has formed an internal committee that is currently evaluating the impact of this update on its Consolidated Financial Statements. In August 2016, the FASB issued an update (ASU 2016-15 Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments) which may change how an entity classifies certain cash receipts and cash payments on its statement of cash flows to reduce diversity in practice. The update also provides guidance on when an entity should separate cash flows and classify them into more than one class and when an entity should classify the aggregate of those cash flows into a single class based on the predominance principle. The guidance in this ASU will become effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted. First Financial does not anticipate this update will have a material impact on its Consolidated Financial Statements. In January 2017, the FASB issued an update (ASU 2017-01, Business Combinations (Topic 805), Clarifying the Definition of a Business) which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The update also provides a more robust framework to use in determining when a set of assets and activities is a business. The guidance in this ASU will become effective for reporting periods beginning after December 15, 2017, and should be applied prospectively on or after the effective date, with early adoption permitted. First Financial does not anticipate this update will have a material impact on its Consolidated Financial Statements. In January 2017, the FASB issued an update (ASU 2017-04, Intangibles - Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment) which simplifies the subsequent measurement of goodwill by eliminating Step 2 from goodwill impairment testing. This update requires an entity to perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount, and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, with any loss recognized not to exceed the total amount of goodwill allocated to that reporting unit. Additionally, the update requires consideration of the income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable, and eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment. First Financial early adopted the provisions set forth in this update in 2017. Adoption of this update did not have a material impact on First Financial's Consolidated Financial Statements. In March 2017, the FASB issued an update (ASU 2017-07, Compensation - Retirement Benefits (Topic 715), Improving the Presentation of the Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost) which requires disaggregation of the service cost component from the other components of net benefit cost. This update also provides explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allows only the service cost component of net benefit cost to be eligible for capitalization. The guidance in this ASU will become effective for reporting periods beginning after December 15, 2017, with early adoption permitted. First Financial does not anticipate this update will have a material impact on its Consolidated Financial Statements, but will result in updated disclosures. In March 2017, the FASB issued an update (ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities) which amends the amortization period for certain purchased callable debt securities held at a premium and shortens the amortization period for the premium to the earliest call date rather than as an adjustment of yield over the contractual life of the instrument. This update more closely aligns the amortization period of premiums and discounts to expectations incorporated in market pricing on the underlying securities, as in most cases, market participants price securities to the call date that produces the worst yield when the coupon is above current market rates (that is, the security is trading at a premium) and price securities to maturity when the coupon is below market rates (that is, the security is trading at a discount) in anticipation that the borrower will act in its economic best interest in an attempt to more closely align interest income recorded on bonds held at a premium or a discount with the economics of the underlying instrument. The guidance in this ASU will become effective for reporting periods, beginning after December 15, 2018, with early adoption permitted. First Financial is currently evaluating the impact of this update on its Consolidated Financial Statements. In May 2017, the FASB issued an update (ASU 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting), which provides clarity and reduces the diversity in practice, cost and complexity when accounting for a change to the terms or conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718 clarifying that an entity will not apply modification accounting to a share-based payment award if the award's fair value (or calculated value or intrinsic value), vesting conditions and classification as an equity or liability instrument are the same immediately before and after the change. The guidance in this ASU will become effective for reporting periods beginning after December 15, 2017, with early adoption permitted and will be applied prospectively to an award modified on or after the adoption date. First Financial does not anticipate this update will have a material impact on its Consolidated Financial Statements. In August 2017, the FASB issued an update (ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities) to better align financial reporting for hedging activities with the economic objectives of those activities. This update aligns certain aspects of hedge documentation, effectiveness assessments, accounting and disclosures, and expands permissible hedge strategies as of the date of adoption. The guidance in this ASU will become effective for reporting periods beginning after December 15, 2018, with early adoption permitted, and will require a modified retrospective transition method with recognition of the cumulative effect of the change on the opening balance of each affected component of equity. Amended disclosures will be required prospectively. First Financial is currently evaluating the impact of this update on its Consolidated Financial Statements. In February 2018, the FASB issued an update (ASU 2018-02, Income statement-Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income), which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. Consequently, the amendments eliminated the stranded tax effects resulting from the Tax Cuts and Jobs Act and will improve the usefulness of information reported to financial statement users. The amendments only relate to the reclassification of the income tax effects of the Tax Cuts and Jobs Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not effected. The amendments in this update also require certain disclosures about stranded tax effects. The guidance in this ASU will become effective for reporting periods beginning after December 15, 2018, with early adoption permitted, and will be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized. As a result of the guidance in this ASU, First Financial anticipates reclassifying $4.9 million from accumulated other comprehensive income to retained earnings during the first quarter of 2018.

RESTRICTIONS ON CASH AND DIVIDE

RESTRICTIONS ON CASH AND DIVIDENDS	12 Months Ended
	Dec. 31, 2017
Subsidiaries [Member]
Restrictions on Subsidiary Dividends, Loans or Advances [Line Items]
Restrictions On Cash And Dividends [Text Block]	Restrictions On Cash And Dividends First Financial is required by the FRB to hold cash in reserve against deposit liabilities when total reservable deposit liabilities exceed the regulatory exemption known as the reserve requirement. The reserve requirement is calculated based on a two-week average of daily net transaction account deposits as defined by the FRB and may be satisfied with average vault cash during the following two-week maintenance period. When vault cash is not sufficient to meet the reserve requirement, the remaining amount must be satisfied with average funds held at the FRB. First Financial's deposit at the FRB is recorded in Interest-bearing deposits with other banks on the Consolidated Balance Sheets. The average required reserve balances, based upon the average level of First Financial's transaction deposits were $66.7 million and $58.9 million for 2017 and 2016 , respectively. Dividends paid by First Financial to its shareholders are principally funded through dividends paid to the Company by its subsidiaries, however, certain restrictions exist regarding the ability of the Bank to transfer funds to First Financial in the form of cash dividends, loans or advances. The approval of the Federal Reserve Board and the Ohio Division of Financial Institutions is required for the Bank to pay dividends in excess of the regulatory limit, which is equal to the net income of the current year through the dividend date, combined with the Bank's retained net income from the two preceding years. As of December 31, 2017 , First Financial's subsidiaries had retained earnings of $546.5 million , of which $163.1 million was available for distribution to First Financial without prior regulatory approval.

INVESTMENTS

INVESTMENTS	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	Investment Securities The following is a summary of held-to-maturity and available-for-sale investment securities as of December 31, 2017 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized cost Unrecognized gain Unrecognized loss Fair value Amortized cost Unrealized gain Unrealized loss Fair value U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (1 ) $ 97 Securities of U.S. government agencies and corporations 11,168 0 (76 ) 11,092 15,695 220 0 15,915 Mortgage-backed securities - residential 162,093 2,042 (1,535 ) 162,600 290,793 849 (2,599 ) 289,043 Mortgage-backed securities - commercial 255,027 1,372 (3,000 ) 253,399 150,356 164 (1,417 ) 149,103 Collateralized mortgage obligations 143,545 354 (1,602 ) 142,297 306,095 1,158 (1,861 ) 305,392 Obligations of state and other political subdivisions 82,175 1,804 (266 ) 83,713 124,269 2,162 (676 ) 125,755 Asset-backed securities 0 0 0 0 377,655 1,628 (306 ) 378,977 Other securities 0 0 0 0 83,266 2,147 (287 ) 85,126 Total $ 654,008 $ 5,572 $ (6,479 ) $ 653,101 $ 1,348,227 $ 8,328 $ (7,147 ) $ 1,349,408 The following is a summary of held-to-maturity and available-for-sale investment securities as of December 31, 2016 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized Unrecognized Unrecognized Fair Amortized Unrealized Unrealized Fair U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (1 ) $ 97 Securities of U.S. government agencies and corporations 13,011 0 (110 ) 12,901 7,056 0 (40 ) 7,016 Mortgage-backed securities - residential 205,522 1,740 (1,166 ) 206,096 184,960 1,175 (2,740 ) 183,395 Mortgage-backed securities - commercial 278,728 3,254 (1,817 ) 280,165 154,239 188 (826 ) 153,601 Collateralized mortgage obligations 195,408 1,125 (1,476 ) 195,057 232,701 634 (2,321 ) 231,014 Obligations of state and other political subdivisions 70,585 117 (1,346 ) 69,356 96,934 1,461 (1,514 ) 96,881 Asset-backed securities 0 0 0 0 322,708 517 (2,013 ) 321,212 Other securities 0 0 0 0 46,641 741 (728 ) 46,654 Total $ 763,254 $ 6,236 $ (5,915 ) $ 763,575 $ 1,045,337 $ 4,716 $ (10,183 ) $ 1,039,870 During the year ended December 31, 2017 , proceeds on the sale of $190.0 million of available-for-sale securities resulted in gains of $1.8 million and losses of $0.2 million . During the year ended December 31, 2016 , proceeds on the sale of $207.0 million of available-for-sale securities resulted in gains of $1.2 million and losses of $1.0 million . During the year ended December 31, 2015 , proceeds on the sale of $70.2 million of available-for-sale securities resulted in gains of $1.5 million and losses of $1 thousand . The carrying value of investment securities pledged as collateral to secure public deposits, repurchase agreements and for other purposes as required by law totaled $819.4 million at December 31, 2017 and $1.0 billion at December 31, 2016 . The following table provides a summary of investment securities by contractual maturity as of December 31, 2017 , except for residential and commercial mortgage-backed securities, collateralized mortgage obligations and asset-backed securities, which are shown as single totals, due to the unpredictability of the timing in principal repayments: Held-to-maturity Available-for-sale (Dollars in thousands) Amortized cost Fair value Amortized cost Fair value Due in one year or less $ 165 $ 165 $ 2,422 $ 2,423 Due after one year through five years 4,492 4,494 37,064 37,149 Due after five years through ten years 2,500 2,723 82,404 84,168 Due after ten years 86,186 87,423 101,438 103,153 Mortgage-backed securities - residential 162,093 162,600 290,793 289,043 Mortgage-backed securities - commercial 255,027 253,399 150,356 149,103 Collateralized mortgage obligations 143,545 142,297 306,095 305,392 Asset-backed securities 0 0 377,655 378,977 Total $ 654,008 $ 653,101 $ 1,348,227 $ 1,349,408 Unrealized gains and losses on debt securities are generally due to fluctuations in current market yields relative to the yields of the debt securities at their amortized cost. All securities with unrealized losses are reviewed quarterly to determine if any impairment is considered other than temporary, requiring a write-down to fair value. First Financial considers the percentage loss on a security, duration of the loss, average life or duration of the security, credit rating of the security and payment performance as well as the Company’s intent and ability to hold the security to maturity when determining whether any impairment is other than temporary. At this time First Financial does not intend to sell, and it is not more likely than not that the Company will be required to sell debt securities temporarily impaired prior to maturity or recovery of the recorded value. First Financial had no other than temporary impairment related to its investment securities portfolio as of December 31, 2017 or 2016 . As of December 31, 2017 , the Company's investment securities portfolio consisted of 775 securities, of which 237 securities were in an unrealized loss position. As of December 31, 2016, the Company's investment securities portfolio consisted of 706 securities, of which 255 were in an unrealized loss position. The following tables provide the fair value and gross unrealized losses on investment securities in an unrealized loss position, aggregated by investment category and the length of time the individual securities have been in a continuous loss position: December 31, 2017 Less than 12 months 12 months or more Total (Dollars in thousands) Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss U.S. Treasuries $ 97 $ (1 ) $ 0 $ 0 $ 97 $ (1 ) Securities of U.S. government agencies and corporations 11,092 (76 ) 0 0 11,092 (76 ) Mortgage-backed securities - residential 175,183 (1,109 ) 108,782 (3,025 ) 283,965 (4,134 ) Mortgage-backed securities - commercial 132,818 (1,713 ) 72,139 (2,704 ) 204,957 (4,417 ) Collateralized mortgage obligations 164,909 (1,138 ) 101,436 (2,325 ) 266,345 (3,463 ) Obligations of state and other political subdivisions 38,450 (507 ) 21,639 (435 ) 60,089 (942 ) Asset-backed securities 44,941 (200 ) 24,396 (106 ) 69,337 (306 ) Other securities 2,605 (1 ) 7,124 (286 ) 9,729 (287 ) Total $ 570,095 $ (4,745 ) $ 335,516 $ (8,881 ) $ 905,611 $ (13,626 ) December 31, 2016 Less than 12 months 12 months or more Total (Dollars in thousands) Fair Unrealized Fair Unrealized Fair Unrealized U.S. Treasuries $ 97 $ (1 ) $ 0 $ 0 $ 97 $ (1 ) Securities of U.S. Government agencies and corporations 19,917 (150 ) 0 0 19,917 (150 ) Mortgage-backed securities - residential 180,654 (3,621 ) 9,890 (285 ) 190,544 (3,906 ) Mortgage-backed securities - commercial 123,122 (1,200 ) 65,007 (1,443 ) 188,129 (2,643 ) Collateralized mortgage obligations 201,305 (2,882 ) 42,314 (915 ) 243,619 (3,797 ) Obligations of state and other political subdivisions 94,632 (2,710 ) 12,023 (150 ) 106,655 (2,860 ) Asset-backed securities 116,057 (764 ) 92,629 (1,249 ) 208,686 (2,013 ) Other securities 7,746 (237 ) 21,357 (491 ) 29,103 (728 ) Total $ 743,530 $ (11,565 ) $ 243,220 $ (4,533 ) $ 986,750 $ (16,098 ) For further detail on the fair value of investment securities, see Note 20 – Fair Value Disclosures.

LOANS

LOANS	12 Months Ended
	Dec. 31, 2017
Loans [Abstract]
LOANS (excluding covered loans)	Loans and Leases First Financial offers clients a variety of commercial and consumer loan and lease products with various interest rates and payment terms. Commercial loan categories include commercial and industrial, commercial real estate, construction real estate and lease financing. Consumer loan categories include residential real estate, home equity, installment and credit card. Lending activities are primarily concentrated in states where the Bank operates banking centers (Ohio, Indiana and Kentucky). First Financial also offers two nationwide lending platforms, one that provides equipment and leasehold improvement financing for franchisees in the quick service and casual dining restaurant sector and another that provides loans primarily to insurance agents and brokers that are secured by commissions and cash collateral accounts. Credit quality. To facilitate the monitoring of credit quality for commercial loans, and for purposes of determining an appropriate ALLL, First Financial utilizes the following categories of credit grades: Pass - Higher quality loans that do not fit any of the other categories described below. Special Mention - First Financial assigns a special mention rating to loans and leases with potential weaknesses that deserve management's close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or lease or in First Financial's credit position at some future date. Substandard - First Financial assigns a substandard rating to loans or leases that are inadequately protected by the current sound financial worth and paying capacity of the borrower or the collateral pledged, if any. Substandard loans and leases have well-defined weaknesses that jeopardize repayment of the debt. Substandard loans and leases are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not addressed. Doubtful - First Financial assigns a doubtful rating to loans and leases with all of the attributes of a substandard rating with the added characteristic that the weaknesses make collection or liquidation in full highly questionable and improbable, on the basis of currently existing facts, conditions and values. The possibility of loss is extremely high, but because of certain important and reasonably specific pending factors that may work to the advantage and strengthening of the credit quality of the loan or lease, its classification as an estimated loss is deferred until its more exact status may be determined. Pending factors include proposed merger, acquisition or liquidation procedures, capital injection, perfecting liens on additional collateral and refinancing plans. The credit grades described above, which are derived from standard regulatory rating definitions, are assigned upon initial approval of credit to borrowers and updated periodically thereafter. First Financial considers repayment performance as the best indicator of credit quality for consumer loans. Consumer loans that have principal and interest payments that are past due by 90 days or more are generally classified as nonperforming. Additionally, consumer loans that have been modified in a TDR are classified as nonperforming. Purchased impaired loans are not classified as nonperforming as the loans are considered to be performing under FASB ASC Topic 310-30. Commercial and consumer credit exposure by risk attribute was as follows: As of December 31, 2017 Real Estate (Dollars in thousands) Commercial and industrial Construction Commercial Lease financing Total Pass $ 1,882,464 $ 467,687 $ 2,446,999 $ 88,078 $ 4,885,228 Special Mention 6,226 0 4,436 0 10,662 Substandard 24,053 43 38,656 1,269 64,021 Doubtful 0 0 0 0 0 Total $ 1,912,743 $ 467,730 $ 2,490,091 $ 89,347 $ 4,959,911 Residential real estate Home Equity Installment Credit card Total Performing $ 463,459 $ 489,148 $ 41,331 $ 46,691 $ 1,040,629 Nonperforming 7,932 4,456 255 0 12,643 Total $ 471,391 $ 493,604 $ 41,586 $ 46,691 $ 1,053,272 As of December 31, 2016 Real Estate (Dollars in thousands) Commercial and industrial Construction Commercial Lease financing Total Pass $ 1,725,451 $ 398,155 $ 2,349,662 $ 92,540 $ 4,565,808 Special Mention 18,256 1,258 15,584 108 35,206 Substandard 38,241 21 62,331 460 101,053 Doubtful 0 0 0 0 0 Total $ 1,781,948 $ 399,434 $ 2,427,577 $ 93,108 $ 4,702,067 Residential real estate Home equity Installment Credit card Total Performing $ 491,380 $ 456,314 $ 50,202 $ 43,408 $ 1,041,304 Nonperforming 9,600 4,074 437 0 14,111 Total $ 500,980 $ 460,388 $ 50,639 $ 43,408 $ 1,055,415 Delinquency. Loans are considered past due or delinquent when the contractual principal or interest due in accordance with the terms of the loan agreement or any portion thereof remains unpaid after the due date of the scheduled payment. Loan delinquency, including nonaccrual loans, was as follows: As of December 31, 2017 (Dollars in thousands) 30 – 59 days past due 60 – 89 days past due > 90 days past due Total past due Current Subtotal Purchased impaired Total > 90 days past due and still accruing Loans Commercial and industrial $ 755 $ 1,657 $ 5,078 $ 7,490 $ 1,901,821 $ 1,909,311 $ 3,432 $ 1,912,743 $ 0 Lease financing 485 0 0 485 88,862 89,347 0 89,347 0 Construction real estate 234 0 0 234 467,216 467,450 280 467,730 0 Commercial real estate 1,716 201 8,777 10,694 2,419,969 2,430,663 59,428 2,490,091 0 Residential real estate 526 811 1,992 3,329 430,500 433,829 37,562 471,391 0 Home equity 2,716 394 1,753 4,863 485,127 489,990 3,614 493,604 0 Installment 179 29 205 413 40,529 40,942 644 41,586 0 Credit card 285 87 62 434 46,257 46,691 0 46,691 62 Total $ 6,896 $ 3,179 $ 17,867 $ 27,942 $ 5,880,281 $ 5,908,223 $ 104,960 $ 6,013,183 $ 62 As of December 31, 2016 (Dollars in thousands) 30 - 59 days past due 60 - 89 days past due > 90 days past due Total past due Current Subtotal Purchased impaired Total > 90 days past due and still accruing Loans Commercial and industrial $ 1,257 $ 208 $ 1,339 $ 2,804 $ 1,773,939 $ 1,776,743 $ 5,205 $ 1,781,948 $ 0 Lease financing 137 0 115 252 92,856 93,108 0 93,108 0 Construction real estate 0 0 0 0 398,877 398,877 557 399,434 0 Commercial real estate 777 134 5,589 6,500 2,339,327 2,345,827 81,750 2,427,577 2,729 Residential real estate 821 37 2,381 3,239 450,631 453,870 47,110 500,980 0 Home equity 195 145 1,776 2,116 456,143 458,259 2,129 460,388 0 Installment 24 1 258 283 49,058 49,341 1,298 50,639 0 Credit card 457 177 142 776 42,632 43,408 0 43,408 142 Total $ 3,668 $ 702 $ 11,600 $ 15,970 $ 5,603,463 $ 5,619,433 $ 138,049 $ 5,757,482 $ 2,871 Nonaccrual. 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 collection of future principal and interest payments is no longer doubtful. 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 provision for loan and lease losses or prospective yield adjustments. Troubled debt restructurings. A loan modification is considered a TDR when the borrower is experiencing financial difficulty and 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 restructured terms of the loan agreement. First Financial had 214 TDRs totaling $23.9 million at December 31, 2017 , including $17.5 million of loans on accrual status and $6.4 million of loans classified as nonaccrual. First Financial had an insignificant amount of commitments outstanding to lend additional funds to borrowers whose loan terms have been modified through TDRs, and the ALLL included reserves of $1.3 million related to TDRs as of December 31, 2017 . For the years ended December 31, 2017 , 2016 and 2015 , First Financial charged off $0.3 million , $0.5 million and $2.7 million , respectively, for the portion of TDRs determined to be uncollectible. Additionally, as of December 31, 2017 , approximately $17.2 million of the accruing TDRs have been performing in accordance with the restructured terms for more than one year. First Financial had 247 TDRs totaling $35.4 million at December 31, 2016 , including $30.2 million of loans on accrual status and $5.1 million of loans classified as nonaccrual. First Financial had $0.9 million of commitments outstanding to lend additional funds to borrowers whose loan terms have been modified through TDRs. At December 31, 2016 the ALLL included reserves of $1.9 million related to TDRs, and $22.6 million of the accruing TDRs had been performing in accordance with the restructured terms for more than one year. First Financial had 271 TDRs totaling $38.2 million at December 31, 2015 , including $28.9 million of loans on accrual status and $9.3 million of loans classified as nonaccrual. First Financial had $1.8 million of commitments outstanding to lend additional funds to borrowers whose loan terms have been modified through TDRs. At December 31, 2015 , the ALLL included reserves of $6.3 million related to TDRs, and $10.3 million of the accruing TDRs had been performing in accordance with the restructured terms for more than one year. The following table provides information on loan modifications classified as TDRs during the years ended December 31, 2017 , 2016 and 2015 : Years ended December 31, 2017 2016 2015 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial and industrial 7 $ 5,724 $ 5,661 18 $ 3,402 $ 3,508 33 $ 9,035 $ 8,203 Construction real estate 0 0 0 0 0 0 0 0 0 Commercial real estate 8 1,816 1,758 16 5,200 4,752 18 20,249 16,474 Residential real estate 6 416 315 5 840 787 10 1,292 1,238 Home equity 1 39 39 5 165 156 25 2,859 2,221 Installment 0 0 0 3 9 9 10 97 97 Total 22 $ 7,995 $ 7,773 47 $ 9,616 $ 9,212 96 $ 33,532 $ 28,233 The following table provides information on how TDRs were modified during the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Extended maturities $ 3,261 $ 2,571 $ 12,883 Adjusted interest rates 2,767 0 0 Combination of rate and maturity changes 489 3,046 1,244 Forbearance 1,181 88 260 Other (1) 75 3,507 13,846 Total $ 7,773 $ 9,212 $ 28,233 (1) Other includes covenant modifications and other concessions or combination of concessions that do not consist of interest rate adjustments, forbearance and maturity extensions. First Financial considers repayment performance as an indication of the effectiveness of the Company's loan modifications. Borrowers that are 90 days or more past due on any principal or interest payments, or who prematurely terminate a restructured loan agreement without paying off the contractual principal balance (for example, in a deed-in-lieu arrangement), are considered to be in payment default of the terms of the TDR agreement. For the twelve months ended December 31, 2017 , 2016 and 2015 , there were one , four and ten TDRs, respectively, with balances of $1.5 million , $0.3 million and $1.6 million , respectively, for which there was a payment default during the period that occurred within twelve months of the loan modification. Impaired loans. Loans classified as nonaccrual and loans modified as TDRs are considered impaired. The following table provides information on impaired loans, excluding purchased impaired loans, as of December 31: (Dollars in thousands) 2017 2016 2015 Impaired loans Nonaccrual loans (1) Commercial and industrial $ 5,229 $ 2,419 $ 8,405 Lease financing 82 195 122 Construction real estate 29 0 0 Commercial real estate 10,616 6,098 9,418 Residential real estate 4,140 5,251 5,027 Home equity 3,743 3,400 4,898 Installment 243 367 127 Total nonaccrual loans 24,082 17,730 27,997 Accruing troubled debt restructurings 17,545 30,240 28,876 Total impaired loans $ 41,627 $ 47,970 $ 56,873 Interest income effect Gross amount of interest that would have been recorded under original terms $ 3,397 $ 2,848 $ 3,595 Interest included in income Nonaccrual loans 535 375 475 Troubled debt restructurings 710 876 682 Total interest included in income 1,245 1,251 1,157 Net impact on interest income $ 2,152 $ 1,597 $ 2,438 Commitments outstanding to borrowers with nonaccrual loans $ 0 $ 0 $ 1 (1) Nonaccrual loans include nonaccrual TDRs of $6.4 million , $5.1 million and $9.3 million as of December 31, 2017 , 2016 and 2015 , respectively. First Financial individually reviews all impaired commercial loan relationships greater than $250,000 , as well as consumer loan TDRs greater than $250,000 , to determine if a specific 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. Specific 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. First Financial's investment in impaired loans, excluding purchased impaired loans, is as follows: December 31, 2017 December 31, 2016 (Dollars in thousands) Current balance Contractual principal balance Related allowance Current balance Contractual Related Loans with no related allowance recorded Commercial and industrial $ 7,162 $ 8,460 $ 0 $ 12,134 $ 12,713 $ 0 Lease financing 82 82 0 195 195 0 Construction real estate 29 60 0 0 0 0 Commercial real estate 18,423 20,837 0 12,232 14,632 0 Residential real estate 6,876 8,145 0 8,412 9,648 0 Home equity 4,356 5,399 0 3,973 5,501 0 Installment 255 422 0 437 603 0 Total 37,183 43,405 0 37,383 43,292 0 Loans with an allowance recorded Commercial and industrial 169 169 169 1,069 1,071 550 Lease financing 0 0 0 0 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 3,119 3,120 448 8,228 8,277 593 Residential real estate 1,056 1,063 160 1,189 1,189 179 Home equity 100 100 2 101 101 2 Installment 0 0 0 0 0 0 Total 4,444 4,452 779 10,587 10,638 1,324 Total Commercial and industrial 7,331 8,629 169 13,203 13,784 550 Lease financing 82 82 0 195 195 0 Construction real estate 29 60 0 0 0 0 Commercial real estate 21,542 23,957 448 20,460 22,909 593 Residential real estate 7,932 9,208 160 9,601 10,837 179 Home equity 4,456 5,499 2 4,074 5,602 2 Installment 255 422 0 437 603 0 Total $ 41,627 $ 47,857 $ 779 $ 47,970 $ 53,930 $ 1,324 Years ended December 31, 2017 2016 2015 (Dollars in thousands) Average balance Interest Average balance Interest income recognized Average Interest Loans with no related allowance recorded Commercial and industrial $ 13,167 $ 280 $ 13,619 $ 309 $ 10,468 $ 258 Lease financing 112 4 150 3 24 0 Construction real estate 601 1 0 0 150 0 Commercial real estate 20,935 563 14,252 357 19,363 344 Residential real estate 7,616 196 7,752 199 8,143 184 Home equity 4,032 99 4,830 86 5,648 82 Installment 332 4 366 7 380 7 Total 46,795 1,147 40,969 961 44,176 875 Loans with an allowance recorded Commercial and industrial 1,204 28 1,098 37 1,409 26 Lease financing 0 0 214 8 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 2,634 40 7,792 211 12,928 213 Residential real estate 1,112 26 1,374 30 1,696 40 Home equity 101 4 101 4 101 3 Installment 0 0 0 0 0 0 Total 5,051 98 10,579 290 16,134 282 Total Commercial and industrial 14,371 308 14,717 346 11,877 284 Lease financing 112 4 364 11 24 0 Construction real estate 601 1 0 0 150 0 Commercial real estate 23,569 603 22,044 568 32,291 557 Residential real estate 8,728 222 9,126 229 9,839 224 Home equity 4,133 103 4,931 90 5,749 85 Installment 332 4 366 7 380 7 Total $ 51,846 $ 1,245 $ 51,548 $ 1,251 $ 60,310 $ 1,157 OREO. OREO is comprised of properties acquired by the Company primarily through the loan foreclosure or repossession process, or other resolution activities that result in partial or total satisfaction of problem loans. Changes in OREO were as follows: Years ended December 31, (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 6,284 $ 13,254 $ 22,674 Additions Commercial 1,732 1,850 5,187 Residential 2,387 1,022 3,211 Total additions 4,119 2,872 8,398 Disposals Commercial (5,409 ) (6,993 ) (12,722 ) Residential (1,574 ) (2,363 ) (3,095 ) Total disposals (6,983 ) (9,356 ) (15,817 ) Valuation adjustments Commercial (439 ) (345 ) (1,617 ) Residential (200 ) (141 ) (384 ) Total valuation adjustments (639 ) (486 ) (2,001 ) Balance at end of year $ 2,781 $ 6,284 $ 13,254 FDIC indemnification asset. The FDIC indemnification asset results from the loss sharing agreements entered into in conjunction with First Financial's FDIC-assisted transactions, and represents expected reimbursements from the FDIC for losses on covered assets. First Financial's FDIC indemnification asset balance was $1.9 million and $12.0 million as of December 31, 2017 and 2016 , respectively. The accounting for FDIC indemnification assets is closely related to the accounting for the underlying, indemnified assets as well as on-going assessment of the collectibility of the indemnification assets. The primary activities impacting the FDIC indemnification asset are FDIC claims, amortization, FDIC loss sharing income and accelerated discount. In December 2017, First Financial reached a preliminary agreement with the FDIC to early terminate its loss sharing agreements. As such, First Financial recorded a $5.1 million impairment charge to its indemnification asset as a component of noninterest expense as all future recoveries, gains, losses and expenses related to these previously covered assets will now be recognized entirely by First Financial given the FDIC will no longer share in such gains or losses.

ALLOWANCE FOR LOAN AND LEASE LO

ALLOWANCE FOR LOAN AND LEASE LOSSES	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
ALLOWANCE FOR LOAN AND LEASE LOSSES	Allowance for Loan and Lease Losses Loans and leases. Management maintains the ALLL at a level that it considers sufficient to absorb probable incurred loan and lease losses inherent in the portfolio. Management determines the adequacy of the ALLL 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. For further discussion of First Financial's allowance methodology, see Note 1 – Summary of Significant Accounting Policies. The ALLL 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 from the liquidation of collateral. During 2015, First Financial closed its merger with Oak Street. Loans acquired in this transaction were recorded at estimated fair value at the acquisition date with no carryover of the related ALLL. Covered/formerly covered loans. The majority of covered/formerly covered loans are purchased impaired loans, whereby First Financial is required to periodically re-estimate the expected cash flows. For further detail regarding accounting for purchased impaired loans and the related allowance, see Note 1 – Summary of Significant Accounting Policies. Changes in the ALLL for the three years ended December 31 were as follows: (Dollars in thousands) 2017 2016 2015 Changes in the ALLL, excluding covered/formerly covered loans Balance at beginning of year $ 49,422 $ 43,149 $ 42,820 Provision for loan and lease losses 8,038 9,322 7,926 Loans charged-off (12,712 ) (6,652 ) (11,660 ) Recoveries 4,124 3,603 4,063 Balance at end of year $ 48,872 $ 49,422 $ 43,149 Changes in the ALLL for covered/formerly covered loans Balance at beginning of year $ 8,539 $ 10,249 $ 10,038 Provision for loan and lease losses (4,456 ) 818 1,715 Loans charged-off (951 ) (4,462 ) (8,896 ) Recoveries 2,017 1,934 7,392 Balance at end of year $ 5,149 $ 8,539 $ 10,249 Total changes in the ALLL Balance at beginning of year $ 57,961 $ 53,398 $ 52,858 Provision for loan and lease losses 3,582 10,140 9,641 Loans charged-off (13,663 ) (11,114 ) (20,556 ) Recoveries 6,141 5,537 11,455 Balance at end of year $ 54,021 $ 57,961 $ 53,398 Changes in the ALLL by loan category as of December 31 were as follows: 2017 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Provision for loan and lease losses 6,917 (42 ) 207 (7,291 ) 1,695 1,778 (90 ) 408 3,582 Gross charge-offs (10,194 ) 0 (1 ) (1,038 ) (435 ) (913 ) (225 ) (857 ) (13,663 ) Recoveries 1,650 1 89 2,719 215 1,027 234 206 6,141 Total net charge-offs (8,544 ) 1 88 1,681 (220 ) 114 9 (651 ) (7,522 ) Ending allowance for loan and lease losses $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 2016 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 16,995 $ 821 $ 1,810 $ 23,656 $ 4,014 $ 3,943 $ 386 $ 1,773 $ 53,398 Provision for loan and lease losses 3,705 (106 ) 1,280 5,365 (655 ) (175 ) 53 673 10,140 Gross charge-offs (2,630 ) 0 (93 ) (4,983 ) (387 ) (1,445 ) (386 ) (1,190 ) (11,114 ) Recoveries 1,155 1 285 2,502 236 720 335 303 5,537 Total net charge-offs (1,475 ) 1 192 (2,481 ) (151 ) (725 ) (51 ) (887 ) (5,577 ) Ending allowance for loan and lease losses $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 2015 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 13,870 $ 435 $ 1,045 $ 27,086 $ 3,753 $ 4,260 $ 407 $ 2,002 $ 52,858 Provision for loan and lease losses 4,809 384 597 1,439 1,234 573 25 580 9,641 Gross charge-offs (5,408 ) 0 (85 ) (10,083 ) (1,531 ) (1,891 ) (509 ) (1,049 ) (20,556 ) Recoveries 3,724 2 253 5,214 558 1,001 463 240 11,455 Total net charge-offs (1,684 ) 2 168 (4,869 ) (973 ) (890 ) (46 ) (809 ) (9,101 ) Ending allowance for loan and lease losses $ 16,995 $ 821 $ 1,810 $ 23,656 $ 4,014 $ 3,943 $ 386 $ 1,773 $ 53,398 The ALLL balance and the recorded investment in loans by portfolio segment and based on impairment method as of December 31 were as follows: December 31, 2017 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Ending allowance on loans individually evaluated for impairment $ 169 $ 0 $ 0 $ 448 $ 160 $ 2 $ 0 $ 0 $ 779 Ending allowance on loans collectively evaluated for impairment 17,429 675 3,577 20,482 4,523 4,933 307 1,316 53,242 Ending allowance for loan and lease losses $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 Loans and Leases Ending balance of loans individually evaluated for impairment $ 7,331 $ 82 $ 29 $ 21,542 $ 7,932 $ 4,456 $ 255 $ 0 $ 41,627 Ending balance of loans collectively evaluated for impairment 1,905,412 89,265 467,701 2,468,549 463,459 489,148 41,331 46,691 5,971,556 Total loans $ 1,912,743 $ 89,347 $ 467,730 $ 2,490,091 $ 471,391 $ 493,604 $ 41,586 $ 46,691 $ 6,013,183 December 31, 2016 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance on loans individually evaluated for impairment $ 550 $ 0 $ 0 $ 593 $ 179 $ 2 $ 0 $ 0 $ 1,324 Ending allowance on loans collectively evaluated for impairment 18,675 716 3,282 25,947 3,029 3,041 388 1,559 56,637 Ending allowance for loan and lease losses $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Loans and Leases Ending balance of loans individually evaluated for impairment $ 13,203 $ 195 $ 0 $ 20,460 $ 9,601 $ 4,074 $ 437 $ 0 $ 47,970 Ending balance of loans collectively evaluated for impairment 1,768,745 92,913 399,434 2,407,117 491,379 456,314 50,202 43,408 5,709,512 Total loans $ 1,781,948 $ 93,108 $ 399,434 $ 2,427,577 $ 500,980 $ 460,388 $ 50,639 $ 43,408 $ 5,757,482

PREMISES AND EQUIPMENT

PREMISES AND EQUIPMENT	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
PREMISES AND EQUIPMENT	Premises and Equipment Premises and equipment at December 31 were as follows: (Dollars in thousands) 2017 2016 Land and land improvements $ 41,711 $ 41,112 Buildings 104,576 107,918 Furniture and fixtures 55,165 55,368 Leasehold improvements 19,377 19,544 Construction in progress 1,721 3,791 222,550 227,733 Less: Accumulated depreciation and amortization 97,514 96,154 Total $ 125,036 $ 131,579 Rental expense recorded under operating leases in 2017 , 2016 and 2015 was $7.1 million , $7.9 million and $7.0 million , respectively. First Financial's future minimum lease payments for operating leases are as follows: (Dollars in thousands) 2018 $ 6,468 2019 6,212 2020 5,962 2021 5,161 2022 3,112 Thereafter 8,346 Total $ 35,261

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	Goodwill and Other Intangible Assets Goodwill. Assets and liabilities acquired in a business combination 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. During 2017 and 2016, First Financial did not record any additions to goodwill. Additions to goodwill in 2015 resulted from the acquisition of Oak Street. Changes in the carrying amount of goodwill for the years ended December 31, 2017 , 2016 and 2015 are shown below. (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 204,084 $ 204,084 $ 137,739 Goodwill resulting from business combinations 0 0 66,345 Balance at end of year $ 204,084 $ 204,084 $ 204,084 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. First Financial performed its annual impairment test of goodwill as of October 1, 2017 and no impairment was indicated. As of December 31, 2017 , no events or changes in circumstances indicated that the fair value of a reporting unit was below its carrying value. Other intangible assets. As of December 31, 2017 and 2016 , First Financial had $5.3 million and $6.5 million , respectively, of other intangibles which primarily consist of core deposit intangibles and are included in Goodwill and other intangibles in the Consolidated Balance Sheets. Core deposit intangibles represent the estimated fair value of acquired customer deposit relationships. Core deposit intangibles are recorded at fair value on the date of acquisition and are then amortized on an accelerated basis over their estimated useful lives. Core deposit intangibles were $3.3 million and $4.5 million as of December 31, 2017 and December 31, 2016 , respectively. First Financial recorded no additions to core deposit intangibles in 2017 or 2016. First Financial's core deposit intangibles have an estimated weighted average remaining life of 3.9 years as of December 31, 2017 . Amortization expense recognized on intangible assets for 2017 , 2016 and 2015 was $1.3 million , $1.6 million and $1.9 million , respectively. The estimated amortization expense of intangible assets for the next five years is as follows: (Dollars in thousands) Amortization Expense 2018 $ 1,097 2019 1,020 2020 788 2021 636 2022 189

DEPOSITS

DEPOSITS	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposit Liabilities Disclosures [Text Block]	Deposits Time deposits that meet or exceed the FDIC insurance limit of $250,000 at December 31, 2017 and 2016 were $174.8 million and $190.9 million , respectively. Scheduled maturities of time deposits for the next five years were as follows: (Dollars in thousands) Total 2018 $ 783,451 2019 315,274 2020 122,165 2021 68,532 2022 27,394 Thereafter 289 Total $ 1,317,105

BORROWINGS

BORROWINGS	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
BORROWINGS	Borrowings Short-term borrowings on the Consolidated Balance Sheets include repurchase agreements utilized for corporate sweep accounts with cash management account agreements in place, overnight advances from the FHLB and a short-term line of credit. All repurchase agreements are subject to terms and conditions of repurchase/security agreements between the Bank and the client. The Bank is authorized to sell or repurchase U.S. Treasury, government agency and mortgage-backed securities to secure its liability to the client. First Financial has a $15.0 million short-term credit facility with an unaffiliated bank that matures on May 29, 2018. This facility can have a variable or fixed interest rate and provides First Financial additional liquidity for various corporate activities, including the repurchase of First Financial shares and the payment of dividends to shareholders. As of December 31, 2017 and December 31, 2016 , there was no outstanding balance. The credit agreement requires First Financial to comply with certain covenants including those related to asset quality and capital levels, and First Financial was in compliance with all covenants associated with this facility as of December 31, 2017 and December 31, 2016 . The following is a summary of short-term borrowings for the last three years: 2017 2016 2015 (Dollars in thousands) Amount Rate Amount Rate Amount Rate At December 31, Federal funds purchased and securities sold under agreements to repurchase $ 72,265 0.19 % $ 120,212 0.12 % $ 89,325 0.11 % FHLB borrowings 742,300 1.43 % 687,700 0.66 % 849,100 0.47 % Total $ 814,565 1.32 % $ 807,912 0.58 % $ 938,425 0.44 % Average for the year Federal funds purchased and securities sold under agreements to repurchase $ 69,766 0.19 % $ 89,157 0.05 % $ 73,191 0.07 % FHLB borrowings 760,558 1.05 % 791,259 0.55 % 552,360 0.24 % Other short-term borrowings 41 4.07 % 41 3.56 % 123 3.30 % Total $ 830,365 0.98 % $ 880,457 0.50 % $ 625,674 0.22 % Maximum month-end balances Federal funds purchased and securities sold under agreements to repurchase $ 130,633 $ 122,242 $ 123,374 FHLB borrowings 957,700 1,035,000 849,100 Other short-term borrowings 0 0 15,000 In 2015, First Financial issued $120.0 million of subordinated notes, which have a fixed interest rate of 5.13% payable semiannually and mature in August 2025. These notes are not redeemable by the Company or callable by the holders of the notes prior to maturity. The subordinated notes are treated as Tier 2 capital for regulatory capital purposes and are included in Long-term debt on the Consolidated Balance Sheets. Long-term debt also includes FHLB long-term advances as of December 31, 2017 and 2016 . These instruments are primarily utilized to reduce overnight liquidity risk and to mitigate interest rate sensitivity on the Consolidated Balance Sheets. FHLB advances, both short-term and long-term, must be collateralized with qualifying assets, typically certain commercial and residential real estate loans, as well as certain government and agency securities. For ease of borrowing execution, First Financial utilizes a blanket collateral agreement with the FHLB, and at December 31, 2017 , had collateral pledged with a book value of $3.6 billion . The following is a summary of First Financial's long-term debt: 2017 2016 (Dollars in thousands) Amount Average Rate Amount Average Rate Subordinated debt $ 120,000 5.13 % $ 120,000 5.13 % Unamortized debt issuance costs (1,362 ) n/a (1,537 ) n/a FHLB 241 1.09 % 351 1.43 % Capital loan with municipality 775 0.00 % 775 0.00 % Total long-term debt $ 119,654 5.14 % $ 119,589 5.15 % As of December 31, 2017 , First Financial's long-term debt matures as follows: (Dollars in thousands) Long-term debt 2018 $ 15 2019 226 2020 0 2021 0 2022 0 Thereafter 119,413 Total $ 119,654

DERIVATIVES

DERIVATIVES	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	Derivatives First Financial uses certain derivative instruments, including rate caps, floors and swaps, to meet the needs of its clients while managing the interest rate risk associated with certain transactions. First Financial does not use derivatives for speculative purposes. For discussion of First Financial's accounting for derivative instruments, see Note 1 – Summary of Significant Accounting Policies. First Financial primarily utilizes interest rate swaps as a means to offer borrowers credit-based products that meet their needs and may also utilize interest rate swaps to manage the interest rate risk profile of the Company. Interest rate payments are exchanged with counterparties, based on the notional amount as established in the swap agreement. As only interest rate payments are exchanged, the cash requirements and credit risk associated with interest rate swaps are significantly less than the notional amount and the Company’s credit risk exposure is limited to the market value of the instruments. First Financial manages this market value credit risk through counterparty credit policies, which 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 . The Company is currently below all single counterparty and portfolio limits. At December 31, 2017 , the Company had a total counterparty notional amount outstanding of $837.5 million , spread among thirteen counterparties, with an outstanding liability from these contracts of $1.3 million . At December 31, 2016 , the Company had a total counterparty notional amount outstanding of $677.8 million , spread among ten counterparties, with an outstanding liability from these contracts of $5.2 million . First Financial’s exposure to credit loss, in the event of nonperformance by a borrower, is limited to the market value of the derivative instrument associated with that borrower. First Financial monitors its derivative credit exposure to borrowers by monitoring the creditworthiness of the related loan customers through the normal credit review processes the Company performs on all borrowers. Additionally, the Company monitors derivative credit risk exposure related to problem loans through the Company's ALLL committee. First Financial considers the market value of a derivative instrument to be part of the carrying value of the related loan for these purposes as the borrower is contractually obligated to pay First Financial this amount in the event the derivative contract is terminated. Client derivatives. First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets. The following table details the location and amounts recognized in the Consolidated Balance Sheets for client derivatives: December 31, 2017 December 31, 2016 Estimated fair value Estimated fair value (Dollars in thousands) Balance Sheet Location Notional amount Gain Loss Notional amount Gain Loss Client derivatives Matched interest rate swaps with borrower Accrued interest and other assets and other liabilities $ 837,040 $ 7,153 $ (5,529 ) $ 677,028 $ 8,401 $ (4,158 ) Matched interest rate swaps with counterparty Accrued interest and other liabilities 837,040 5,529 (7,158 ) 677,028 4,158 (8,429 ) Total $ 1,674,080 $ 12,682 $ (12,687 ) $ 1,354,056 $ 12,559 $ (12,587 ) In connection with its use of derivative instruments, First Financial and its counterparties are required to post cash collateral to offset the market position of the derivative instruments under certain conditions. First Financial maintains the right to offset these derivative positions with the collateral posted against them by or with the relevant counterparties. First Financial classifies the derivative cash collateral outstanding with its counterparties as an adjustment to the fair value of the derivative contracts within Accrued interest and other assets or Accrued interest and other liabilities in the Consolidated Balance Sheets. The following table discloses the gross and net amounts of assets and liabilities recognized in the Consolidated Balance Sheets: December 31, 2017 December 31, 2016 (Dollars in thousands) Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of assets presented in the Consolidated Balance Sheets Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of assets presented in the Consolidated Balance Sheets Client derivatives Matched interest rate swaps $ 12,687 $ 2,279 $ 14,966 $ 12,587 $ (462 ) $ 12,125 The following table details the derivative financial instruments, the average remaining maturities and the weighted-average interest rates being paid and received by First Financial at December 31, 2017 : Weighted-Average Rate (Dollars in thousands) Notional amount Average maturity (years) Fair value Receive Pay Client derivatives Receive fixed, matched interest rate swaps with borrower $ 837,040 5.9 $ 1,624 4.37 % 3.66 % Pay fixed, matched interest rate swaps with counterparty 837,040 5.9 (1,629 ) 3.66 % 4.37 % Total client derivatives $ 1,674,080 5.9 $ (5 ) 4.01 % 4.01 % Credit derivatives. 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. The total notional value of these agreements totaled $95.9 million as of December 31, 2017 and $64.9 million as of December 31, 2016 . The fair value of these agreements were recorded in Accrued interest and other liabilities on the Consolidated Balance Sheets. Mortgage Derivatives. 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 an IRLC with First Financial and the loan is 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 and loans held for sale. At December 31, 2017 , the notional amount of the IRLCs was $12.3 million and the notional amount of forward commitments was $15.4 million . As of December 31, 2016 , the notional amount of IRLCs was $13.2 million and the notional amount of forward commitments was $17.8 million . The fair value of these agreements was recorded on the Consolidated Balance Sheets in Accrued interest and other assets and was $0.1 million at December 31, 2017 and $0.2 million at December 31, 2016 .

RELATED PARTIES TRANSACTIONS

RELATED PARTIES TRANSACTIONS	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Loans to Related Parties	Related Party Transactions Loans to directors, executive officers, principal holders of First Financial’s common stock and certain related persons were as follows: (Dollars in thousands) 2017 Beginning balance $ 6,930 Additions 3,904 Deductions (961 ) Ending balance $ 9,873 Loans 90 days or more past due $ 0 Related parties of First Financial, as defined for inclusion in the table above, were clients of, and had transactions with, subsidiaries of First Financial during the periods noted. Similar transactions with related parties may be expected in future periods.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	Commitments and Contingencies First Financial offers a variety of financial instruments with off-balance sheet risk to its clients to assist them in meeting their requirement 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 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 nonperformance, is represented by the contractual amounts of those instruments. First Financial utilizes the ALLL methodology to maintain a reserve that it considers sufficient to absorb probable losses incurred in standby letters of credit and outstanding loan commitments and records the reserve within Accrued interest and other liabilities on the Consolidated Balance Sheets. Loan commitments. Loan commitments are agreements to extend credit to a client absent any violation of any condition 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 are expected to expire without being 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. First Financial had commitments outstanding to extend credit, totaling $2.1 billion and $2.0 billion at December 31, 2017 and December 31, 2016 , respectively. As of December 31, 2017 , loan commitments with a fixed interest rate totaled $44.3 million while commitments with variable interest rates totaled $2.0 billion . The fixed rate loan commitments have interest rates ranging from 0.00% to 21.00% and maturities ranging from 1 to 29 years . Letters of credit. Letters of credit are conditional commitments issued by First Financial to guarantee the performance of a client to a third party. First Financial’s portfolio of standby letters of credit consists primarily 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. First Financial has issued letters of credit (including standby letters of credit) aggregating $25.3 million and $18.4 million at December 31, 2017 , and December 31, 2016 , respectively. Management conducts regular reviews of these instruments on an individual client basis. Investments in affordable housing projects. First Financial has investments in certain qualified affordable housing tax credits. These credits are an indirect federal subsidy that provide tax incentives to encourage investment in the development, acquisition and rehabilitation of affordable rental housing, and allow investors to claim tax credits and other tax benefits (such as deductions from taxable income for operating losses) on their federal income tax returns. The principal risk associated with qualified affordable housing investments is the potential for noncompliance with the tax code requirements, such as failure to rent property to qualified tenants, resulting in the unavailability or recapture of the tax credits and other tax benefits. First Financial's affordable housing commitments totaled $35.9 million and $32.7 million as of December 31, 2017 and December 31, 2016 , respectively. The Company recognized tax credits of $3.2 million and $2.1 million related to its investments in affordable housing projects for the years ended December 31, 2017 and 2016 , respectively. The Company recognized amortization expense which was included in income tax expense of $4.2 million and $2.7 million for the years ended December 31, 2017 and 2016 , respectively. First Financial had no affordable housing contingent commitments as of December 31, 2017 or December 31, 2016 . Investments in historic tax credits. First Financial has noncontrolling financial investments in private investment funds and partnerships which are not consolidated. These investments may generate a return through the realization of federal and state income tax credits, as well as other tax benefits, such as tax deductions from net operating losses of the investments over a period of time. The Company’s recorded investment in these entities was approximately $3.0 million at December 31, 2017 , and $4.9 million at December 31, 2016 . The maximum exposure to loss related to these investments was $3.0 million at December 31, 2017 and $13.7 million at December 31, 2016 , representing the Company’s investment balance and its unfunded commitments to invest additional amounts. Investments in historic tax credits resulted in $13.7 million and $0.6 million of tax credits for the years ended December 31, 2017 and 2016 , respectively. Recognition of a significant historic tax credit investment resulted in a $12.5 million reduction in income tax expense and $11.3 million of other noninterest expenses during 2017. Contingencies/Litigation. First Financial and its subsidiaries are engaged in various matters of litigation, assertions of improper or fraudulent loan practices or lending violations and other matters from time to time, and have a number of unresolved claims pending. Additionally, as part of the ordinary course of business, First Financial and its subsidiaries are parties to litigation involving claims to the ownership of funds in particular accounts, the collection of delinquent accounts, challenges to security interests in collateral and foreclosure interests, that is incidental to our regular business activities. While the ultimate liability with respect to these other litigation matters and claims cannot be determined at this time, First Financial believes that damages, if any, and other amounts relating to pending matters are not probable or cannot be reasonably estimated as of December 31, 2017 . Reserves are established for these various matters of litigation, when appropriate, under FASB ASC Topic 450, Contingencies, based in part upon the advice of legal counsel. First Financial had no reserves related to litigation matters as of December 31, 2017 or December 31, 2016 .

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	Income Taxes Income tax expense consisted of the following components: (Dollars in thousands) 2017 2016 2015 Current expense Federal $ 22,599 $ 40,537 $ 31,428 State 1,265 1,322 250 Total current expense 23,864 41,859 31,678 Deferred (benefit) expense Federal (4,657 ) 528 3,980 State 169 (182 ) 212 Total deferred (benefit) expense (4,488 ) 346 4,192 Income tax expense $ 19,376 $ 42,205 $ 35,870 The difference between the federal income tax rates, applied to income before income taxes, and the effective rates were due to the following: (Dollars in thousands) 2017 2016 2015 Income taxes computed at federal statutory rate (35%) on income before income taxes $ 40,657 $ 45,756 $ 38,827 Benefit from tax-exempt income (3,427 ) (2,911 ) (2,815 ) Tax credits (16,806 ) (2,691 ) (1,388 ) Tax rate reduction impact (8,191 ) 0 0 Basis reduction on historic tax credit 4,599 0 0 Tax benefit of equity compensation (1,449 ) (72 ) (35 ) State income taxes, net of federal tax benefit 932 741 301 Affordable housing investments 2,798 1,923 455 Other 263 (541 ) 525 Income tax expense $ 19,376 $ 42,205 $ 35,870 On December 22, 2017, the Tax Cuts and Jobs Act was signed into law. As a result, First Financial revalued its deferred tax assets and liabilities as well as its investments in affordable housing projects utilizing a 21% federal rate compared to a 35% rate in prior periods. As a result, the Company recorded an $8.2 million tax benefit in 2017. The major components of the temporary differences that give rise to deferred tax assets and liabilities at December 31, 2017 , and 2016 , were as follows: (Dollars in thousands) 2017 2016 Deferred tax assets Allowance for loan and lease losses $ 12,134 $ 20,955 Deferred compensation 384 627 Postretirement benefits other than pension liability 564 925 Accrued stock-based compensation 932 1,094 Other real estate owned write-downs 97 888 Interest on nonaccrual loans 616 844 Accrued expenses 3,051 5,081 Net unrealized losses on investment securities and derivatives 249 3,141 Other 708 453 Total deferred tax assets 18,735 34,008 Deferred tax liabilities Tax depreciation greater than book depreciation (2,510 ) (5,166 ) FHLB and FRB stock (3,384 ) (5,535 ) Mortgage-servicing rights (343 ) (530 ) Leasing activities (2,792 ) (4,933 ) Prepaid pension (8,888 ) (12,539 ) Intangible assets (11,559 ) (16,611 ) Deferred loan fees and costs (371 ) (1,238 ) Prepaid expenses (210 ) (348 ) Partnership investments (1,230 ) (1,218 ) Fair value adjustments on acquisitions 0 (1,404 ) Other (2,415 ) (852 ) Total deferred tax liabilities (33,702 ) (50,374 ) Total net deferred tax liability $ (14,967 ) $ (16,366 ) The realization of the Company’s deferred tax assets is dependent upon the Company’s ability to generate taxable income in future periods, the reversal of deferred tax liabilities during the same period and the ability to carryback any losses. The Company has evaluated the available evidence supporting the realization of its deferred tax assets and determined it is more likely than not that the assets will be realized and thus no valuation allowance was required at December 31, 2017 and 2016 . Unrecognized tax benefits At December 31, 2017 and 2016 , First Financial had $2.9 million and $2.4 million of unrecognized tax benefits, as determined in FASB ASC Topic 740-10, Income Taxes, that, if recognized, would favorably affect the effective income tax rate in future periods. A progression of unrecognized tax benefits as of December 31, 2017 and 2016 is as follows: (Dollars in thousands) 2017 2016 Balance at beginning of year $ 3,735 $ 0 Additions for tax positions of prior years 0 3,735 Balance at end of year $ 3,735 $ 3,735 The unrecognized tax benefits relate to state income tax exposures where First Financial believes it is likely that, upon examination, a state may take a position contrary to the position taken by the Company. The Company believes that resolution regarding our uncertain tax positions is reasonably possible within the next twelve months and could result in full, partial or no recognition of the benefit. First Financial recognizes interest accrued related to unrecognized tax benefits and penalties as income tax expense. At December 31, 2017 and 2016, the Company had no interest or penalties recorded. First Financial and its subsidiaries are subject to U.S. federal income tax as well as state and local income tax in several jurisdictions. Tax years prior to 2014 have been closed and are no longer subject to U.S. federal income tax examinations. Tax years 2014 through 2016 remain open to examination by the federal taxing authority. First Financial is no longer subject to state and local income tax examinations for years prior to 2011. Tax years 2011 through 2016 remain open to state and local examination by various other jurisdictions.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	Employee Benefit Plans Pension plan. First Financial sponsors a non-contributory defined benefit pension plan covering substantially all employees and uses a December 31 measurement date for the plan. Plan assets were primarily invested in equity mutual funds and fixed income mutual funds. The pension plan does not directly own any shares of First Financial common stock or any other First Financial security or product. The investment objective of the Plan is to structure the assets to mirror the liabilities of the Plan, with the fixed income component matching the identified near and long-term plan distributions and the equity component generating growth of capital to meet other future Plan liabilities. The determination of the overall expected long-term return on plan assets was based on the composition of plan assets and a consensus of estimates from similarly managed portfolios of expected future returns. As a result of the plan’s updated actuarial projections for 2017 , First Financial recorded income related to its pension plan of $0.6 million for 2017 , $1.2 million for 2016 and $1.0 million for 2015 . First Financial made no cash contributions to the pension plan in 2017 , 2016 or 2015 . The following tables set forth information concerning amounts recognized in First Financial's Consolidated Balance Sheets and Consolidated Statements of Income related to the Company's pension plan: December 31, (Dollars in thousands) 2017 2016 Change in benefit obligation Benefit obligation at beginning of year $ 62,729 $ 60,664 Service cost 4,894 5,034 Interest cost 2,325 2,262 Actuarial (gain) loss 6,107 142 Benefits paid, excluding settlement (4,901 ) (5,373 ) Benefit obligation at end of year 71,154 62,729 Change in plan assets Fair value of plan assets at beginning of year 131,011 125,714 Actual return on plan assets 18,239 10,670 Benefits paid, excluding settlement (4,901 ) (5,373 ) Fair value of plan assets at end of year 144,349 131,011 Amounts recognized in the Consolidated Balance Sheets Assets 73,195 68,282 Liabilities 0 0 Net amount recognized $ 73,195 $ 68,282 Amounts recognized in accumulated other comprehensive income (loss) Net actuarial loss $ 33,580 $ 38,278 Net prior service cost (1,921 ) (2,334 ) Deferred tax assets (12,028 ) (13,141 ) Net amount recognized $ 19,631 $ 22,803 Change in accumulated other comprehensive income (loss) $ (3,172 ) $ (1,245 ) Accumulated benefit obligation $ 69,678 $ 61,909 Components of net periodic benefit cost December 31, (Dollars in thousands) 2017 2016 2015 Service cost $ 4,894 $ 5,034 $ 4,807 Interest cost 2,325 2,262 2,120 Expected return on assets (9,358 ) (9,644 ) (9,444 ) Amortization of prior service cost (413 ) (413 ) (413 ) Recognized net actuarial loss 1,924 1,608 1,888 Net periodic benefit (income) cost (628 ) (1,153 ) (1,042 ) Other changes recognized in accumulated other comprehensive income (loss) Net actuarial (gain) loss (2,775 ) (884 ) 11,014 Prior service cost 0 0 0 Amortization of prior service cost 413 413 413 Amortization of gain (1,924 ) (1,608 ) (1,888 ) Total recognized in accumulated other comprehensive income (loss) (4,286 ) (2,079 ) 9,539 Total recognized in net periodic benefit cost and accumulated other comprehensive income (loss) $ (4,914 ) $ (3,232 ) $ 8,497 Amount expected to be recognized in net periodic pension expense in the coming year Amortization of (gain) loss $ 2,090 $ 1,754 $ 1,642 Amortization of prior service credit (413 ) (413 ) (413 ) Pension plan assumptions December 31, 2017 2016 2015 Benefit obligations Discount rate 3.43 % 3.88 % 4.05 % Rate of compensation increase 3.50 % 3.50 % 3.50 % Net periodic benefit cost Discount rate 3.88 % 4.05 % 3.76 % Expected return on plan assets 7.25 % 7.50 % 7.50 % Rate of compensation increase 3.50 % 3.50 % 3.50 % The fair value of the plan assets as of December 31, 2017 by asset category is shown in the table that follows: Fair Value Measurements (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Asset Category Cash $ 175 $ 175 $ 0 $ 0 U. S. Government agencies 6,853 0 6,853 0 Fixed income mutual funds 69,154 69,154 0 0 Equity mutual funds 68,167 68,167 0 0 Total $ 144,349 $ 137,496 $ 6,853 $ 0 The fair value of the plan assets as of December 31, 2016 by asset category is shown in the table that follows: Fair Value Measurements (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Asset Category Cash $ 190 $ 190 $ 0 $ 0 U. S. Government agencies 6,026 0 6,026 0 Fixed income mutual funds 66,483 66,483 0 0 Equity mutual funds 58,311 58,311 0 0 Total $ 131,010 $ 124,984 $ 6,026 $ 0 The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement. See Note 20 – Fair Value Disclosures for further information related to the framework for measuring fair value and the fair value hierarchy. The following benefit payments, which reflect expected future service, are expected to be paid: (Dollars in thousands) Retirement Benefits 2018 $ 4,758 2019 4,426 2020 5,417 2021 5,771 2022 5,016 Thereafter 29,825 401(k) thrift plan. First Financial sponsors a defined contribution 401(k) thrift plan which covers substantially all employees. Employees may contribute up to 50.0% of their earnings into the plan, not to exceed applicable limitations prescribed by the Internal Revenue Service. First Financial's contributions to the 401(k) plan are discretionary and vest immediately. First Financial measures the Company's performance compared to its identified peer group in determining whether to recommend a Company contribution, with the amount of the recommended contribution not to exceed 3% of the employee's annual earnings. First Financial recorded $1.9 million and $0.8 million of expense related to the Company's contributions to the 401(k) plan during the years ended December 31, 2017 and 2016 , respectively. First Financial made no contributions to the 401(k) plan during 2015 . Bank-owned life insurance. First Financial purchases life insurance policies on the lives of certain employees and is the owner and beneficiary of the policies. The Bank invests in these policies to provide an efficient form of funding for long-term retirement and other employee benefits costs. The policies are included within Accrued interest and other assets in the Consolidated Balance Sheets at each policy’s respective cash surrender value with changes recorded in Other noninterest income in the Consolidated Statements of Income. The carrying value of bank-owned life insurance policies was $102.3 million and $98.5 million at December 31, 2017 , and 2016 , respectively.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
	Dec. 31, 2017
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	Accumulated Other Comprehensive Income (Loss) Shareholders’ equity is affected by transactions and valuations of asset and liability positions that require adjustments to accumulated other comprehensive income (loss). The related tax effects allocated to other comprehensive income and accumulated other comprehensive income (loss) are as follows: December 31, 2017 Total other comprehensive income (loss) Total accumulated other (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 8,447 $ 1,649 $ 6,798 $ (2,431 ) $ 4,367 $ (4,549 ) $ 4,367 $ (182 ) Unrealized gain (loss) on derivatives 810 0 810 (296 ) 514 (1,091 ) 514 (577 ) Retirement obligation 2,775 (1,511 ) 4,286 (1,114 ) 3,172 (22,803 ) 3,172 (19,631 ) Total $ 12,032 $ 138 $ 11,894 $ (3,841 ) $ 8,053 $ (28,443 ) $ 8,053 $ (20,390 ) December 31, 2016 Total other comprehensive income (loss) Total accumulated other (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 751 $ 234 $ 517 $ (133 ) $ 384 $ (4,933 ) $ 384 $ (4,549 ) Unrealized gain (loss) on derivatives 809 0 809 (301 ) 508 (1,599 ) 508 (1,091 ) Retirement obligation 884 (1,195 ) 2,079 (834 ) 1,245 (24,048 ) 1,245 (22,803 ) Total $ 2,444 $ (961 ) $ 3,405 $ (1,268 ) $ 2,137 $ (30,580 ) $ 2,137 $ (28,443 ) December 31, 2015 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ (2,200 ) $ 1,505 $ (3,705 ) $ 1,278 $ (2,427 ) $ (2,506 ) $ (2,427 ) $ (4,933 ) Unrealized gain (loss) on derivatives (1,020 ) 0 (1,020 ) 370 (650 ) (949 ) (650 ) (1,599 ) Retirement obligation (11,014 ) (1,475 ) (9,539 ) 3,395 (6,144 ) (17,904 ) (6,144 ) (24,048 ) Foreign currency translation 50 0 50 0 50 (50 ) 50 0 Total $ (14,184 ) $ 30 $ (14,214 ) $ 5,043 $ (9,171 ) $ (21,409 ) $ (9,171 ) $ (30,580 ) The following table details the activity reclassified from accumulated other comprehensive income into income during the period: Amount Reclassified from Accumulated Other Comprehensive Income (1) December 31, (Dollars in thousands) 2017 2016 2015 Affected Line Item in the Consolidated Statements of Income Realized gains and losses on securities available-for-sale $ 1,649 $ 234 $ 1,505 Gains on sales of investments securities Defined benefit pension plan Amortization of prior service cost (2) 413 413 413 Salaries and employee benefits Recognized net actuarial loss (2) (1,924 ) (1,608 ) (1,888 ) Salaries and employee benefits Amortization and settlement charges of defined benefit pension items (1,511 ) (1,195 ) (1,475 ) Total reclassifications for the period, before tax $ 138 $ (961 ) $ 30 (1) Negative amounts are debits to profit/loss. (2) Included in the computation of net periodic pension cost (see Note 15 - Employee Benefit Plans for additional details).

CAPITAL

CAPITAL	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
CAPITAL	Capital Risk-based capital. First Financial and its subsidiary, First Financial Bank, are subject to regulatory capital requirements administered by federal banking agencies. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations involve quantitative measures of assets, liabilities and certain off-balance sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators. Failure to meet minimum capital requirements can initiate regulatory action. The Board of Governors of the Federal Reserve System approved a final rule implementing changes intended to strengthen the regulatory capital framework for all banking organizations (Basel III) which became effective January 1, 2015, subject to a phase-in period for certain provisions. Basel III establishes and defines quantitative measures to ensure capital adequacy which require First Financial to maintain minimum amounts and ratios of Common Equity tier 1 capital, total and tier 1 capital to risk-weighted assets and tier 1 capital to average assets (leverage ratio). The rule includes a new minimum ratio of common equity tier 1 capital to risk-weighted assets of 5.750% and a capital conservation buffer of 2.5% of risk-weighted assets that began on January 1, 2016 at 0.625% and will be phased in over a four-year period, increasing by the same amount each subsequent January 1, until fully phased-in on January 1, 2019. Further, Basel III increased the minimum ratio of tier 1 capital to risk-weighted assets increased from 4.00% to 7.250% and and all banks are now subject to a 4.0% minimum leverage ratio. The required total risk-based capital ratio is unchanged. Failure to maintain the required common equity Tier 1 capital conservation buffer will result in potential restrictions on a bank’s ability to pay dividends, repurchase stock and/or pay discretionary compensation to its employees. First Financial's Tier 1 capital is comprised of total shareholders' equity less unrealized gains and losses on investment securities available-for-sale, accounted for under FASB ASC Topic 320, Investments-Debt and Equity Securities, and any amounts resulting from the application of FASB ASC Topic 715, Compensation-Retirement Benefits, that are recorded within accumulated other comprehensive income (loss), intangible assets and any valuation related to mortgage servicing rights. Total risk-based capital consists of Tier 1 capital plus the qualifying allowance for loan and lease losses and gross unrealized gains on equity securities. For purposes of calculating the leverage ratio, average assets represents quarterly average assets less assets ineligible for total risk-based capital including all or portions of intangible assets, mortgage servicing assets and the ALLL. The revised capital requirements also provide strict eligibility criteria for regulatory capital instruments, and the method for calculating risk-weighted assets includes identification of riskier assets which require higher capital allocations, such as highly volatile commercial real estate and nonaccrual loans. The following tables present the actual and required capital amounts and ratios as of December 31, 2017 and 2016 under the Basel III Capital Rules. The minimum required capital amounts presented include the minimum required capital levels based on the phase-in provisions of the Basel III Capital Rules as well as the minimum required capital levels as of January 1, 2019 when the Basel III Capital Rules have been fully phased-in. Capital levels required to be considered "well capitalized" are based upon prompt corrective action regulations, as amended to reflect the changes under the Basel III Capital Rules. All First Financial's regulatory capital ratios exceeded the amounts necessary to be classified as “well capitalized,” and total regulatory capital exceeded the “minimum” requirement by $271.6 million on a consolidated basis. Actual Minimum capital Required to be Minimum capital (Dollars in thousands) Capital Ratio Capital Ratio Capital Ratio Capital Ratio December 31, 2017 Common equity tier 1 capital to risk-weighted assets Consolidated $ 755,735 10.63 % $ 408,746 5.750 % N/A N/A $ 497,604 7.00 % First Financial Bank 794,251 11.21 % 407,220 5.750 % $ 460,336 6.50 % 495,746 7.00 % Tier 1 capital to risk-weighted assets Consolidated 755,839 10.63 % 515,376 7.250 % N/A N/A 604,233 8.50 % First Financial Bank 794,355 11.22 % 513,452 7.250 % $ 566,567 8.00 % 601,978 8.50 % Total capital to risk-weighted assets Consolidated 929,148 13.07 % 657,548 9.250 % N/A N/A 746,406 10.50 % First Financial Bank 856,363 12.09 % 655,093 9.250 % 708,209 10.00 % 743,619 10.50 % Leverage Consolidated 755,839 8.84 % 342,198 4.00 % N/A N/A 342,198 4.00 % First Financial Bank 794,355 9.29 % 342,113 4.00 % 427,642 5.00 % 342,113 4.00 % Actual Minimum capital Required to be Minimum capital (Dollars in thousands) Capital Ratio Capital Ratio Capital Ratio Capital Ratio December 31, 2016 Common equity tier 1 capital to risk-weighted assets Consolidated $ 703,891 10.46 % $ 344,848 5.125 % N/A N/A $ 471,012 7.00 % First Financial Bank 747,151 11.13 % 344,038 5.125 % $ 436,341 6.50 % 469,906 7.00 % Tier 1 capital to risk-weighted assets Consolidated 703,995 10.46 % 445,779 6.625 % N/A N/A 571,943 8.50 % First Financial Bank 747,255 11.13 % 444,732 6.625 % 537,035 8.00 % 570,600 8.50 % Total capital to risk-weighted assets Consolidated 881,158 13.10 % 580,354 8.625 % N/A N/A 706,517 10.50 % First Financial Bank 813,433 12.12 % 578,991 8.625 % 671,294 10.00 % 704,859 10.50 % Leverage Consolidated 703,995 8.60 % 327,562 4.00 % N/A N/A 327,562 4.00 % First Financial Bank 747,255 9.13 % 327,392 4.00 % 409,240 5.00 % 327,392 4.00 % Share repurchases. In October 2012, First Financial's board of directors approved a share repurchase plan under which the Company has the ability to repurchase up to 5,000,000 common shares. The Company did not repurchase any shares under this plan during 2016 or 2017. The Company repurchased 239,967 shares under the 2012 share repurchase plan during 2015 at an average price of $18.75 per share. At December 31, 2017 , 3,509,133 common shares remained available for purchase under this repurchase plan. ATM Offering. In March 2017, First Financial initiated an "at-the-market" equity offering program to provide flexibility with respect to capital planning and to support future growth. First Financial was not active through the ATM program during the period.

STOCK OPTIONS AND AWARDS

STOCK OPTIONS AND AWARDS	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK OPTIONS AND AWARDS	Stock Options and Awards First Financial follows the provisions of FASB ASC Topic 718, Compensation-Stock Compensation, which requires measurement of compensation cost for all stock-based awards at fair value on the date of grant and recognition of compensation expense over the service period for all awards expected to vest. First Financial recorded share-based compensation expense of $5.4 million for the years ended December 31, 2017 and December 31, 2016 and $4.0 million for the year ended December 31, 2015, within salaries and employee benefits expense related to stock options and restricted stock awards. Total unrecognized compensation cost related to non-vested share-based compensation was $5.5 million at December 31, 2017 and is expected to be recognized over a weighted average period of 1.9 years . As of December 31, 2017 , First Financial had three active stock-based compensation plans: the 1999 Plan, the 2012 Stock Plan, and the Amended and Restated 2012 Stock Plan (each as described below), however additional awards may only be granted under the Amended and Restated 2012 Stock Plan. The 1999 Stock Incentive Plan for Officers and Employees (the 1999 Plan) provided incentive stock options, non-qualified stock options and stock awards to certain key employees of First Financial for up to 7,507,500 common shares. The options become exercisable at a rate of 25% per year on the anniversary date of the grant and remain outstanding for 10 years after the initial grant date with all options expiring at the end of the exercise period. No additional awards may be granted under the 1999 Plan. At December 31, 2017, 11,800 options were outstanding under the 1999 Plan, all of which expire on or before February 14, 2018 . On May 22, 2012, shareholders approved the First Financial Bancorp. 2012 Stock Plan and amendments to the 2009 Non-Employee Director Plan. At December 31, 2017 , there were no shares available for issuance under the 2012 stock plan. On May 23, 2017, the shareholders amended and restated the 2012 Stock Plan as the First Financial Bancorp. Amended and Restated 2012 Stock Plan. At December 31, 2017 , there were 2,154,251 shares available for issuance under the Amended and Restated 2012 Stock Plan. First Financial utilizes the Black-Scholes valuation model to determine the fair value of stock options granted. In addition to the stock option strike price, the Black-Scholes valuation model incorporates the following assumptions: the expected dividend yield based on historical dividend payouts; the expected stock price volatility based on the historical volatility of Company stock for a period approximating the expected life of the options; the risk-free rate based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option; and the expected option life represented by the period of time the options are expected to be outstanding, and is based on historical trends. No options were granted in 2017 , 2016 or 2015 . Stock option activity for the year ended December 31, 2017 , is summarized as follows: (Dollars in thousands, except share and per share data) Number of shares Weighted average exercise price Weighted average remaining contractual life Aggregate intrinsic value Outstanding at beginning of year 113,307 $ 12.08 Granted 0 0.00 Exercised (101,507 ) 12.13 Forfeited or expired 0 0.00 Outstanding at end of year 11,800 $ 11.64 0.12 $ 174 Exercisable at end of year 11,800 $ 11.64 0.12 $ 174 The intrinsic value of stock options is defined as the difference between the current market value and the exercise price. First Financial uses treasury shares purchased under the Company's share repurchase program to satisfy share-based exercises. 2017 2016 2015 Total intrinsic value of options exercised $ 1,533 $ 661 $ 492 Cash received from exercises $ 341 $ 801 $ 744 Tax benefit from exercises $ 1,991 $ 1,958 $ 1,488 Restricted stock awards are recorded at fair value as of the grant date as a component of shareholders' equity and amortized on a straight-line basis to salaries and benefits expense over the specified vesting periods, which is currently three years for employees and one year for non-employee directors. The vesting of these awards for employees and non-employee directors may require a service period to be met, and certain awards may also require performance measures to be met. Activity in restricted stock for the previous three years ended December 31 is summarized as follows: 2017 2016 2015 Number of shares Weighted average grant date fair value Number of shares Weighted average grant date fair value Number of shares Weighted average grant date fair value Nonvested at beginning of year 648,817 $ 17.82 643,641 $ 17.21 494,452 $ 16.43 Granted 234,529 27.36 317,695 18.13 439,674 17.65 Vested (307,825 ) 18.12 (263,713 ) 16.82 (227,905 ) 16.45 Forfeited (107,149 ) 21.18 (48,806 ) 17.37 (62,580 ) 16.58 Nonvested at end of year 468,372 $ 21.63 648,817 $ 17.82 643,641 $ 17.21 The fair value of restricted stock is determined based on the number of shares granted and the quoted price of First Financial's common stock. The fair value of restricted stock vested during 2017 , 2016 and 2015 was $5.6 million , $4.4 million and $3.8 million , respectively.

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	Earnings Per Common Share The following table sets forth the computation of basic and diluted earnings per share: (Dollars in thousands, except share and per share data) 2017 2016 2015 Numerator Net income $ 96,787 $ 88,526 $ 75,063 Denominator Basic earnings per common share - weighted average shares 61,529,460 61,206,093 61,062,657 Effect of dilutive securities Employee stock awards 581,329 729,335 670,282 Warrants 60,801 49,994 114,608 Diluted earnings per common share - adjusted weighted average shares 62,171,590 61,985,422 61,847,547 Earnings per share available to common shareholders Basic $ 1.57 $ 1.45 $ 1.23 Diluted $ 1.56 $ 1.43 $ 1.21 Warrants to purchase 104,200 , 114,678 and 322,312 shares of the Company's common stock were outstanding as of December 31, 2017 , 2016 and 2015 , respectively. These warrants, each representing the right to purchase one share of common stock, no par value per share, have an exercise price of $12.12 and expire on December 23, 2018. Stock options and warrants, with an exercise price greater than the average market price of the common shares, were not included in the computation of net income per diluted share as they would have been antidilutive. Using the period end price, there were no antidilutive options at December 31, 2017 , 2016 , or 2015 . As of December 31, 2017 , 2016 , and 2015 , no preferred shares were issued or outstanding.

FAIR VALUE DISCLOSURES

FAIR VALUE DISCLOSURES	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE DISCLOSURES	Fair Value Disclosures 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 classified in 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 values 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. Other investments. Other investments include holdings in FRB and FHLB stock, which are carried at cost due to the inability to determine the fair value resulting from transferability restrictions. Loans held for sale. Loans held for sale are carried at 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 market price or 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 on the Consolidated Statements of Income. Loans and leases. The fair value of C&I, lease financing, CRE, residential real estate and other consumer loans was 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 loans as Level 3 in the fair value hierarchy. Impaired loans are specifically reviewed for purposes of determining the appropriate amount of impairment to be allocated to the ALLL. 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 upon 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). Impaired loans 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. 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 declines 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. Accrued interest receivable and payable. The carrying amount of accrued interest receivable and accrued interest payable approximate their fair values and is aligned with the underlying assets or liabilities (Level 1, Level 2 or Level 3). Deposits. The fair value of demand deposits, savings accounts and certain money-market deposits represents the amount payable on demand at the reporting date. The carrying amounts for variable-rate CDs approximated their fair values at the reporting date. The fair value of fixed-rate CDs is estimated using a discounted cash flow calculation which applies the interest rates currently offered for deposits of similar remaining maturities. 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. The Company classifies the estimated fair value of long-term debt as Level 2 in the fair value hierarchy. 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 which represents the cost to terminate the swap if First Financial should choose to do so. This net present value is derived using primarily observable market inputs such as interest rate yield curves. 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. The estimated fair values of First Financial's financial instruments not measured at fair value on a recurring or nonrecurring basis in the consolidated financial statements were as follows: Carrying Estimated fair value (Dollars in thousands) value Total Level 1 Level 2 Level 3 December 31, 2017 Financial assets Cash and short-term investments $ 184,624 $ 184,624 $ 184,624 $ 0 $ 0 Investment securities held-to-maturity 654,008 653,101 0 653,101 0 Other investments 53,140 N/A N/A N/A N/A Loans held for sale 11,502 11,502 0 11,502 0 Loans and leases, net of ALLL 5,959,162 6,006,656 0 0 6,006,656 Accrued interest receivable 24,496 24,496 0 8,265 16,231 Financial liabilities Deposits Noninterest-bearing $ 1,662,058 $ 1,662,058 $ 0 $ 1,662,058 $ 0 Interest-bearing demand 1,453,463 1,453,463 0 1,453,463 0 Savings 2,462,420 2,462,420 0 2,462,420 0 Time 1,317,105 1,306,674 0 1,306,674 0 Total deposits 6,895,046 6,884,615 0 6,884,615 0 Short-term borrowings 814,565 814,565 814,565 0 0 Long-term debt 119,654 117,908 0 117,908 0 Accrued interest payable 5,104 5,104 204 4,900 0 Carrying Estimated Fair Value (Dollars in thousands) Value Total Level 1 Level 2 Level 3 December 31, 2016 Financial assets Cash and short-term investments $ 204,048 $ 204,048 $ 204,048 $ 0 $ 0 Investment securities held-to-maturity 763,254 763,575 0 763,575 0 Other investments 51,077 N/A N/A N/A N/A Loans held for sale 13,135 13,135 0 13,135 0 Loans and leases, net of ALLL 5,699,521 5,754,845 0 0 5,754,845 Accrued interest receivable 18,503 18,503 0 5,705 12,798 Financial liabilities Deposits Noninterest-bearing $ 1,547,985 $ 1,547,985 $ 0 $ 1,547,985 $ 0 Interest-bearing demand 1,513,771 1,513,771 0 1,513,771 0 Savings 2,142,189 2,142,189 0 2,142,189 0 Time 1,321,843 1,316,333 0 1,316,333 0 Total deposits 6,525,788 6,520,278 0 6,520,278 0 Short-term borrowings 807,912 807,912 807,912 0 0 Long-term debt 119,589 117,878 0 117,878 0 Accrued interest payable 5,049 5,049 410 4,639 0 The following table summarizes the financial assets and liabilities measured at fair value on a recurring basis: Fair Value Measurements Using Assets/Liabilities (Dollars in thousands) Level 1 Level 2 Level 3 at Fair Value December 31, 2017 Assets Derivatives $ 0 $ 12,757 $ 0 $ 12,757 Investment securities available-for-sale 2,969 1,346,439 0 1,349,408 Total $ 2,969 $ 1,359,196 $ 0 $ 1,362,165 Liabilities Derivatives $ 0 $ 12,755 $ 0 $ 12,755 Fair Value Measurements Using Assets/Liabilities (Dollars in thousands) Level 1 Level 2 Level 3 at Fair Value December 31, 2016 Assets Derivatives $ 0 $ 12,922 $ 0 $ 12,922 Investment securities available-for-sale 8,711 1,031,159 0 1,039,870 Total $ 8,711 $ 1,044,081 $ 0 $ 1,052,792 Liabilities Derivatives $ 0 $ 12,725 $ 0 $ 12,725 Certain financial assets and liabilities are measured at fair value on a nonrecurring basis. Adjustments to the fair market value of these assets and liabilities usually result from the write-downs of individual assets. The following table summarizes financial assets and liabilities measured at fair value on a nonrecurring basis: Fair Value Measurements Using (Dollars in thousands) Level 1 Level 2 Level 3 December 31, 2017 Assets Impaired loans $ 0 $ 0 $ 2,671 OREO 0 0 1,086 Fair Value Measurements Using (Dollars in thousands) Level 1 Level 2 Level 3 December 31, 2016 Assets Impaired loans $ 0 $ 0 $ 8,154 OREO 0 0 3,921

Pending Business Combination wi

Pending Business Combination with MainSource Financial Group	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event, Pro Forma Business Combinations or Disposals	Pending Business Combination (Unaudited) In July 2017, First Financial Bancorp and MainSource Financial Group, Inc. entered into a definitive merger agreement under which MainSource will merge into First Financial in a stock-for-stock transaction. MainSource Bank, a wholly owned subsidiary of MainSource, will merge into First Financial Bank. Under the terms of the merger agreement, shareholders of MainSource will receive 1.3875 common shares of First Financial common stock for each share of MainSource common stock. Including outstanding options and warrants on MainSource common stock, the transaction is valued at approximately $1.0 billion . Upon closing, First Financial shareholders will own approximately 65% of the combined company and MainSource shareholders will own approximately 35% , on a fully diluted basis. The merger will position the combined company to better serve the complimentary geographies of Ohio, Indiana and Kentucky, and create a higher performing bank with greater scale and capabilities. Pro forma information for the periods ended June 30, 2017 and December 31, 2016 was as follows: For the six For the year months ended ended June 30, 2017 December 31, 2016 (Dollars in thousands, except per share data) (Unaudited) (Unaudited) Pro Forma Condensed Combined Income Statement Information Net interest income $ 204,518 $ 387,725 Provision for loan and lease losses 834 10,140 Income before income taxes 92,591 170,132 Net income 65,884 119,661 As of (Unaudited) Pro Forma Condensed Combined Balance Sheet Information Loans and leases, net $ 8,818,392 Total assets 13,806,092 Deposits 9,987,298 Total shareholders' equity 1,913,682 The merger was approved by the FRB of Cleveland and the ODFI during the first quarter of 2018 and is expected to close on April 1, 2018. The selected pro forma financial data included in the preceding table is based on preliminary estimates, and is subject to change upon completion of the merger. In October 2017, the Company filed a registration statement on Form S-4 that included historical and pro forma information required in connection with the merger.

FIRST FINANCIAL BANCORP. (PAREN

FIRST FINANCIAL BANCORP. (PARENT COMPANY ONLY) FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure [Text Block]	First Financial Bancorp (Parent Company Only) Financial Information Balance Sheets December 31, (Dollars in thousands) 2017 2016 Assets Cash $ 57,719 $ 59,285 Investment securities, available for sale 442 386 Subordinated notes from subsidiaries 7,500 7,500 Investment in subsidiaries Commercial banks 970,290 909,798 Total investment in subsidiaries 970,290 909,798 Premises and equipment 1,378 1,395 Other assets 26,778 19,487 Total assets $ 1,064,107 $ 997,851 Liabilities Subordinated debentures $ 118,638 $ 118,463 Dividends payable 10,965 10,386 Other liabilities 3,840 3,778 Total liabilities 133,443 132,627 Shareholders’ equity 930,664 865,224 Total liabilities and shareholders’ equity $ 1,064,107 $ 997,851 Statements of Income Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Income Interest income $ 6 $ 48 $ 81 Noninterest income 86 2,596 253 Dividends from subsidiaries 54,600 52,700 17,250 Total income 54,692 55,344 17,584 Expenses Interest expense 6,152 6,151 2,157 Salaries and employee benefits 5,519 5,445 4,224 Miscellaneous professional services 970 711 723 Other 4,819 4,841 5,564 Total expenses 17,460 17,148 12,668 Income before income taxes and equity in undistributed net earnings of subsidiaries 37,232 38,196 4,916 Income tax benefit (7,080 ) (5,302 ) (4,563 ) Equity in undistributed earnings (loss) of subsidiaries 52,475 45,028 65,584 Net income $ 96,787 $ 88,526 $ 75,063 Statements of Cash Flows Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Operating activities Net income $ 96,787 $ 88,526 $ 75,063 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed (earnings) loss of subsidiaries (52,475 ) (45,028 ) (65,584 ) Depreciation and amortization 193 192 78 Stock-based compensation expense 5,446 5,354 4,049 Deferred income taxes (360 ) 584 (85 ) (Decrease) increase in dividends payable 579 135 2 (Decrease) increase in other liabilities (889 ) (389 ) 1,965 Decrease (increase) in other assets (6,951 ) (9,065 ) 1,459 Net cash provided by (used in) operating activities 42,330 40,309 16,947 Investing activities Capital contributions to subsidiaries 0 (53,000 ) (40,000 ) Proceeds from calls and maturities of investment securities 0 5,978 87 Purchases of investment securities 0 (333 ) (412 ) Net cash provided by (used in) investing activities 0 (47,355 ) (40,325 ) Financing activities Proceeds from long-term borrowings 0 0 120,000 Cash dividends paid on common stock (41,178 ) (39,125 ) (39,070 ) Treasury stock purchase 0 0 (4,498 ) Proceeds from exercise of stock options, net of shares purchased 341 801 744 Excess tax benefit on share-based compensation 0 264 146 Other (3,059 ) (1,681 ) (3,064 ) Net cash provided by (used in) financing activities (43,896 ) (39,741 ) 74,258 Net increase (decrease) in cash (1,566 ) (46,787 ) 50,880 Cash at beginning of year 59,285 106,072 55,192 Cash at end of year $ 57,719 $ 59,285 $ 106,072

SUMMARY OF SIGNIFICANT ACCOUN31

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2017
Basis of Presentation Policy	Basis of presentation. The Consolidated Financial Statements of First Financial Bancorp., 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. All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior years' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings.
Use of Estimates, Policy	Use of estimates. The preparation of Consolidated 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. Actual realized amounts could differ materially from those estimates.
Investment, Policy	Investment securities. First Financial classifies debt and equity securities into three categories: held-to-maturity, trading and available-for-sale. Management classifies investment securities into the appropriate category at the time of purchase and re-evaluates that classification as deemed appropriate. Investment securities are classified as held-to-maturity when First Financial has the positive intent and ability to hold the securities to maturity. Held-to-maturity securities are recorded at amortized cost. Investment securities classified as trading are held principally for resale in the near-term and are recorded at fair value. Fair value is determined using quoted market prices. Gains or losses on trading securities, both realized and unrealized, are reported in noninterest income. Investment securities not classified as either held-to-maturity or trading are classified as available-for-sale. Available-for-sale securities are recorded at fair value, with the unrealized gains and losses, net of tax, reported as a separate component of accumulated other comprehensive income (loss) in shareholders' equity. The amortized cost of investment securities classified as either held-to-maturity or available-for-sale is adjusted for amortization of premiums and accretion of discounts to maturity, or in the case of mortgage-backed securities, over the estimated life of the security. Such amortization and accretion are considered an adjustment to the yield on the security and included in interest income from investments. Interest and dividends are included in interest income from investment securities in the Consolidated Statements of Income. Realized gains and losses are based on the amortized cost of the security sold using the specific identification method. Available-for-sale and held-to-maturity securities are reviewed quarterly for potential impairment. In performing this review, management considers the length of time and extent to which the fair value of the security has been less than amortized cost, the financial condition and near-term prospects of the issuer and the ability and intent of First Financial to hold the security for a period sufficient to allow for any anticipated recovery in fair value. If the fair value of a security is less than the amortized cost and the impairment is determined to be other-than-temporary, the security is written down, establishing a new and reduced cost basis. The related charge is recorded in the Consolidated Statements of Income. Other investments. Other investments include holdings in FRB stock and FHLB stock, which are both carried at cost.
Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block]	Loans held for sale. Loans held for sale consists of residential real estate loans newly originated for the purpose of sale to third parties, and in certain circumstances, loans previously originated that have been specifically identified by management for sale based on predetermined criteria. Loans transferred to held for sale status are carried at the lower of cost or fair value. Any subsequent change in the carrying value of transferred loans, not to exceed original cost, is recorded in the Consolidated Statements of Income. The Bank sells loans with servicing retained or released depending on pricing and market conditions.
Finance, Loans and Leases Receivable, Policy	Loans and leases, excluding purchased impaired loans. Loans and leases for which First Financial has the intent and ability to hold for the foreseeable future, or until maturity or payoff, are classified in the Consolidated Balance Sheets as loans and leases. Loans and leases are carried at the principal amount outstanding, net of unamortized deferred loan origination fees and costs, and net of unearned income, with the exception of loans subject to fair value requirements. Loan origination and commitment fees received, as well as certain direct loan origination costs paid, are deferred, and the net amount is amortized as an adjustment to the related loan's yield. Interest income on loans and leases is recorded on an accrual basis. 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 classified as nonaccrual are applied as a reduction to the carrying value of the loan. A loan may return to accrual status if collection of future principal and interest payments is no longer doubtful. Acquired loans. Acquired loans are recorded at their estimated fair value at the time of acquisition. Estimated fair values for acquired loans are based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, interest rate, term of loan, whether or not the loan was amortizing and a discount rate reflecting the Company's assessment of risk inherent in the cash flow estimates. Acquired loans are grouped together according to similar characteristics and treated in the aggregate when applying various valuation techniques. First Financial evaluates acquired loans for impairment in accordance with the provisions of FASB ASC Topic 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality. Acquired loans with evidence of credit deterioration since origination are accounted for under FASB ASC Topic 310-30 and are referred to as purchased impaired loans. 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 purchased impaired loans. Acquired loans outside of the scope of FASB ASC Topic 310-30 are accounted for under FASB ASC Topic 310-20, Receivables-Nonrefundable Fees and Costs. Discounts created when the loans were recorded at their estimated fair values at acquisition are amortized over the remaining term of the loan as an adjustment to the related loan's yield. The accrual of interest income is discontinued when the collection of a loan or interest, in whole or in part, is doubtful. Certain loans acquired in FDIC-assisted transactions were initially covered under loss sharing agreements and are referred to as covered loans during the indemnification period. Subsequent to the indemnification period, they are referred to as formerly covered loans.
Loans and Leases Receivable, Allowance for Loan Losses Policy	Allowance for loan and lease losses. For each reporting period, management maintains the ALLL at a level that it considers sufficient to absorb probable incurred loan and lease losses inherent in the portfolio. Management determines the adequacy of the ALLL 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. Management's determination of the adequacy of the ALLL is based on an assessment of the probable incurred loan and lease losses inherent in the portfolio given the conditions at the time. The ALLL 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 from the liquidation of collateral. Commercial loan and lease relationships (including time and demand notes, tax-exempt loans, C&I, construction, commercial real estate, mezzanine loans and lease financing) greater than $250,000 that are considered impaired, or designated as a TDR, are evaluated to determine the need for a specific allowance based on the borrower's overall financial condition, resources, payment record, guarantor support and the realizable value of any collateral. The allowance for non-impaired commercial loans and leases, as well as impaired commercial loan and lease relationships less than $250,000 , includes a process of estimating the probable losses incurred in the portfolio by loan type, based on First Financial's internal system of credit risk ratings and historical loss data. These estimates may also be adjusted based upon trends in the values of the underlying collateral, delinquent and nonaccrual loans, prevailing economic conditions and changes in lending strategies, among other influencing factors. Consumer loans are generally evaluated by loan type, 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 probable losses incurred 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 greater than $250,000 classified as TDRs are individually evaluated to determine an appropriate allowance. For purchased impaired loans, expected cash flows are re-estimated periodically with declines in gross expected cash flows recorded as provision expense during the period. The related, estimated reimbursement for loan losses due from the FDIC under loss sharing agreements, if applicable, is recorded as FDIC loss sharing income.
Commitments and Contingencies, Policy	Reserve for unfunded commitments . First Financial maintains a reserve that it considers sufficient to absorb probable losses incurred in standby letters of credit and outstanding loan commitments. This reserve is included in Accrued interest and other liabilities on the Consolidated Balance Sheets, First Financial determines the adequacy of the reserve based upon an evaluation of the unfunded credit facilities, which includes consideration of historical commitment utilization experience, credit risk ratings and historical loss rates, consistent with the Company's ALLL methodology. Adjustments to the reserve for unfunded commitments are included in Other noninterest expense in the Consolidated Statements of Income. First Financial offers a variety of financial instruments with off-balance sheet risk to its clients to assist them in meeting their requirement 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 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 nonperformance, is represented by the contractual amounts of those instruments. First Financial utilizes the ALLL methodology to maintain a reserve that it considers sufficient to absorb probable losses incurred in standby letters of credit and outstanding loan commitments and records the reserve within Accrued interest and other liabilities on the Consolidated Balance Sheets.
FDIC Indemnification Assets Policy	FDIC indemnification asset. The FDIC indemnification asset results from the loss sharing agreements entered into in conjunction with First Financial's FDIC-assisted transactions, and represents expected reimbursements from the FDIC for losses on covered assets. The FDIC indemnification asset is measured separately from the related assets covered by loss sharing agreements with the FDIC as it is not contractually embedded in those assets and is not transferable should First Financial choose to dispose of the covered assets. Pursuant to the terms of the loss sharing agreements, covered assets are subject to stated loss thresholds whereby the FDIC will reimburse First Financial for 80% of losses up to the stated loss thresholds, and 95% of losses in excess of the thresholds. The FDIC indemnification asset was recorded at its estimated fair value at the time of the FDIC-assisted transactions. Fair values were estimated using projected cash flows related to the loss sharing agreements based on the expected reimbursements for losses and the applicable loss sharing percentages. These cash flows were discounted to reflect the uncertainty of the timing of the loss sharing reimbursement from the FDIC. The accounting for the FDIC indemnification asset is closely related to the accounting for the underlying, indemnified assets as well as ongoing assessment of the collectibility of the indemnification asset. The primary activities impacting the FDIC indemnification asset are FDIC claims, amortization, FDIC loss sharing income and accelerated discount.
Property, Plant and Equipment, Policy	Premises and equipment. Premises and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are principally computed on the straight-line method over the estimated useful lives of the assets. Useful lives generally range from 10 to 40 years for building and building improvements; 3 to 10 years for furniture, fixtures and equipment; and 3 to 5 years for software, hardware and data handling equipment. Land improvements are depreciated over 20 years and leasehold improvements are depreciated over the lesser of the term of the respective lease or the useful life of the asset. Premises and equipment are evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Maintenance and repairs are expensed as incurred.
Goodwill and Intangible Assets, Policy	Goodwill and other indefinite lived intangible assets. Under accounting for business combinations, the net assets of entities acquired by First Financial are recorded at their estimated fair value at the date of acquisition. The excess cost of the acquisition over the fair value of net assets acquired is recorded as goodwill. Goodwill and intangible assets deemed to have indefinite lives, if any, are not amortized, but are subject to annual impairment tests. The Company is required to evaluate goodwill for impairment on an annual basis or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. First Financial performs its annual impairment test effective October 1, absent events or changes in circumstances that indicate the carrying value of goodwill may not be recoverable. The Company’s goodwill is accounted for in a single reporting unit representing the consolidated entity. Fair value is estimated using the market capitalization of the Company as of the annual impairment testing date. First Financial also utilizes additional information and analyses to corroborate the use of the Company’s market capitalization as a proper indicator of fair value for purposes of the annual goodwill impairment test.
Goodwill and Intangible Assets, Goodwill, Policy	Goodwill. Assets and liabilities acquired in a business combination 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 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. First Financial performed its annual impairment test of goodwill as of October 1, 2017 and no impairment was indicated. As of December 31, 2017 , no events or changes in circumstances indicated that the fair value of a reporting unit was below its carrying value.
Core Deposit Intangibles Policy	Core deposit intangibles. CDI represent the estimated value of acquired customer deposit relationships. CDI are recorded at fair value at the date of acquisition and are based on a discounted cash flow methodology that gives appropriate consideration to expected customer attrition rates, cost of the deposit base, reserve requirements and the net maintenance cost attributable to customer deposits. Core deposit intangibles are amortized on an accelerated basis over their estimated useful lives.
Other Real Estate Owned Policy	Other real estate owned. OREO consists of properties acquired by the Company primarily through the loan foreclosure or repossession process, or other resolution activity that results in partial or total satisfaction of problem loans. OREO properties are recorded at fair value, less estimated disposal costs (net realizable value). Losses arising at the time of acquisition of such properties are charged against the ALLL. Management performs periodic valuations to assess the adequacy of recorded OREO balances and subsequent write-downs in the carrying value of OREO properties are expensed as incurred. Improvements to OREO 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. When management disposes of an OREO property, any gains or losses realized at the time of disposal are reflected in the Consolidated Statements of Income.
Affordable Housing Program Policy	Affordable housing projects. First Financial has investment in certain qualified affordable housing projects. These projects are indirect federal subsidies that provide tax incentives to encourage investment in the development, acquisition and rehabilitation of affordable rental housing, and allow investors to claim tax credits and other tax benefits (such as deductions from taxable income for operating losses) on their federal income tax returns. The principal risk associated with qualified affordable housing investments is the potential for noncompliance with the tax code requirements, such as, failure to rent properties to qualified tenants, resulting in unavailability or recapture of the tax credits and other tax benefits. Investments in affordable housing projects are accounted for under the proportional amortization method and are included in Accrued interest and other assets in the Consolidated Balance Sheets.
Investments in Historic Tax Credits [Policy Text Block]	Investments in historic tax credits. First Financial has noncontrolling financial investments in private investment funds and partnerships which are not consolidated. These investments may generate a return through the realization of federal and state income tax credits, as well as other tax benefits, such as tax deductions from net operating losses of the investments over a period of time. Investments in historic tax credits are accounted for under the equity method of accounting. The Company’s recorded investment in these entities is carried in Accrued interest and other assets on the Consolidated Balance Sheets.
Income Tax, Policy	Income taxes. First Financial and its subsidiaries file a consolidated federal income tax return. Each subsidiary provides for income taxes on a separate return basis, and remits to First Financial amounts determined to be currently payable. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Interest and penalties on income tax assessments or income tax refunds are recognized as a component of noninterest expense in the Consolidated Statements of Income.
Pension and Other Postretirement Plans, Pensions, Policy	Pension. First Financial sponsors a non-contributory defined benefit pension plan covering substantially all employees. The measurement of the accrued benefit liability and the annual pension expense involves actuarial and economic assumptions, which include the discount rate, the expected return on plan assets and the rate of compensation increase.
Derivatives, Policy	Derivative instruments. First Financial accounts for its derivative financial instruments in accordance with FASB ASC Topic 815, Derivatives and Hedging. FASB ASC Topic 815 requires all derivative instruments to be carried at fair value on the balance sheet. The accounting for changes in the fair value of derivatives is based on the intended use of the derivative and the resulting designation. Derivatives used to hedge the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives used to hedge the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Client derivatives - First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets. Upon entering into an interest rate swap with a borrower, the Bank simultaneously enters into an offsetting swap agreement with an institutional counterparty, with substantially matching terms. These matched interest rate swap agreements generally involve the receipt by First Financial of floating rate amounts from the 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. First Financial's matched interest rate swaps qualify as derivatives, but are not designated as hedging instruments. The net interest receivable or payable on matched interest rate swaps is accrued and recognized as an adjustment to interest income. The fair values of back to back swaps are included within Accrued interest and other assets and Accrued interest and other liabilities on the Consolidated Balance Sheets. Credit derivatives - 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. The fair value of these agreements is recorded on the Consolidated Balance Sheets in Accrued interest and other liabilities. Mortgage derivatives - 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 an IRLC with First Financial and the loan is 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 and Loans held for sale. The fair value of these agreements is recorded on the Consolidated Balance Sheets in Accrued interest and other assets.
Share-based Compensation, Option and Incentive Plans Policy	Stock-based compensation. First Financial grants stock-based awards, including restricted stock awards and options to purchase the Company’s common stock. Stock option grants are for a fixed number of shares to employees and directors with an exercise price equal to the fair value of the shares at the date of grant. Stock-based compensation expense is recognized in the Consolidated Statements of Income on a straight-line basis over the vesting period. As compensation expense is recognized, a deferred tax asset is recorded that represents an estimate of the future tax deduction from exercise. At the time stock-based awards are exercised, canceled or expire, First Financial may be required to recognize an adjustment to tax expense.
Earnings Per Share, Policy	Earnings per share. Basic earnings per common share is computed by dividing net income available to common shareholders by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding, unvested shares and dilutive common stock equivalents outstanding during the period. Common stock equivalents, which consist of common stock issuable under the assumed exercise of stock options granted under First Financial's stock-based compensation plans and the assumed conversion of common stock warrants, are calculated using the treasury stock method.
Cash and Cash Equivalents, Policy	Cash and due from banks. Cash and due from banks consist of currency, coin and cash items due from banks. Cash items due from banks include noninterest bearing deposits held at other banks.
Loans and Leases Receivable, Nonaccrual Loan and Lease Status, Policy	Nonaccrual. 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 collection of future principal and interest payments is no longer doubtful. 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 provision for loan and lease losses or prospective yield adjustments.
Impaired Financing Receivable, Policy	Loans classified as nonaccrual and loans modified as TDRs are considered impaired.
Loans and Leases Receivable, Real Estate Acquired Through Foreclosure, Policy	OREO is comprised of properties acquired by the Company primarily through the loan foreclosure or repossession process, or other resolution activities that result in partial or total satisfaction of problem 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 classified in 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 values 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. Other investments. Other investments include holdings in FRB and FHLB stock, which are carried at cost due to the inability to determine the fair value resulting from transferability restrictions. Loans held for sale. Loans held for sale are carried at 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 market price or 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 on the Consolidated Statements of Income. Loans and leases. The fair value of C&I, lease financing, CRE, residential real estate and other consumer loans was 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 loans as Level 3 in the fair value hierarchy. Impaired loans are specifically reviewed for purposes of determining the appropriate amount of impairment to be allocated to the ALLL. 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 upon 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). Impaired loans 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. 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 declines 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. Accrued interest receivable and payable. The carrying amount of accrued interest receivable and accrued interest payable approximate their fair values and is aligned with the underlying assets or liabilities (Level 1, Level 2 or Level 3). Deposits. The fair value of demand deposits, savings accounts and certain money-market deposits represents the amount payable on demand at the reporting date. The carrying amounts for variable-rate CDs approximated their fair values at the reporting date. The fair value of fixed-rate CDs is estimated using a discounted cash flow calculation which applies the interest rates currently offered for deposits of similar remaining maturities. 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. The Company classifies the estimated fair value of long-term debt as Level 2 in the fair value hierarchy. 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 which represents the cost to terminate the swap if First Financial should choose to do so. This net present value is derived using primarily observable market inputs such as interest rate yield curves. 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.
Segment Reporting, Policy	Segments and related information. While the Company monitors the operating results of its four lines of business, operations are managed and financial performance is evaluated on a consolidated basis. Accordingly, and consistent with prior years, all of the Company's operations are considered by management to be aggregated in one reportable operating segment.
Credit Risk
Derivatives, Methods of Accounting, Hedging Derivatives	First Financial manages this market value credit risk through counterparty credit policies, which 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 .
Fair Value Hedges
Derivatives, Methods of Accounting, Hedging Derivatives	First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets.

INVESTMENTS (Tables)

INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Summary of Held-To-Maturity and Available-For-Sale Investment Securities	The following is a summary of held-to-maturity and available-for-sale investment securities as of December 31, 2017 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized cost Unrecognized gain Unrecognized loss Fair value Amortized cost Unrealized gain Unrealized loss Fair value U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (1 ) $ 97 Securities of U.S. government agencies and corporations 11,168 0 (76 ) 11,092 15,695 220 0 15,915 Mortgage-backed securities - residential 162,093 2,042 (1,535 ) 162,600 290,793 849 (2,599 ) 289,043 Mortgage-backed securities - commercial 255,027 1,372 (3,000 ) 253,399 150,356 164 (1,417 ) 149,103 Collateralized mortgage obligations 143,545 354 (1,602 ) 142,297 306,095 1,158 (1,861 ) 305,392 Obligations of state and other political subdivisions 82,175 1,804 (266 ) 83,713 124,269 2,162 (676 ) 125,755 Asset-backed securities 0 0 0 0 377,655 1,628 (306 ) 378,977 Other securities 0 0 0 0 83,266 2,147 (287 ) 85,126 Total $ 654,008 $ 5,572 $ (6,479 ) $ 653,101 $ 1,348,227 $ 8,328 $ (7,147 ) $ 1,349,408 The following is a summary of held-to-maturity and available-for-sale investment securities as of December 31, 2016 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized Unrecognized Unrecognized Fair Amortized Unrealized Unrealized Fair U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (1 ) $ 97 Securities of U.S. government agencies and corporations 13,011 0 (110 ) 12,901 7,056 0 (40 ) 7,016 Mortgage-backed securities - residential 205,522 1,740 (1,166 ) 206,096 184,960 1,175 (2,740 ) 183,395 Mortgage-backed securities - commercial 278,728 3,254 (1,817 ) 280,165 154,239 188 (826 ) 153,601 Collateralized mortgage obligations 195,408 1,125 (1,476 ) 195,057 232,701 634 (2,321 ) 231,014 Obligations of state and other political subdivisions 70,585 117 (1,346 ) 69,356 96,934 1,461 (1,514 ) 96,881 Asset-backed securities 0 0 0 0 322,708 517 (2,013 ) 321,212 Other securities 0 0 0 0 46,641 741 (728 ) 46,654 Total $ 763,254 $ 6,236 $ (5,915 ) $ 763,575 $ 1,045,337 $ 4,716 $ (10,183 ) $ 1,039,870
Summary of Investment Securities by Estimated Maturity	The following table provides a summary of investment securities by contractual maturity as of December 31, 2017 , except for residential and commercial mortgage-backed securities, collateralized mortgage obligations and asset-backed securities, which are shown as single totals, due to the unpredictability of the timing in principal repayments: Held-to-maturity Available-for-sale (Dollars in thousands) Amortized cost Fair value Amortized cost Fair value Due in one year or less $ 165 $ 165 $ 2,422 $ 2,423 Due after one year through five years 4,492 4,494 37,064 37,149 Due after five years through ten years 2,500 2,723 82,404 84,168 Due after ten years 86,186 87,423 101,438 103,153 Mortgage-backed securities - residential 162,093 162,600 290,793 289,043 Mortgage-backed securities - commercial 255,027 253,399 150,356 149,103 Collateralized mortgage obligations 143,545 142,297 306,095 305,392 Asset-backed securities 0 0 377,655 378,977 Total $ 654,008 $ 653,101 $ 1,348,227 $ 1,349,408
Age of Gross Unrealized Losses and Associated Fair Value by Investment Category	The following tables provide the fair value and gross unrealized losses on investment securities in an unrealized loss position, aggregated by investment category and the length of time the individual securities have been in a continuous loss position: December 31, 2017 Less than 12 months 12 months or more Total (Dollars in thousands) Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss U.S. Treasuries $ 97 $ (1 ) $ 0 $ 0 $ 97 $ (1 ) Securities of U.S. government agencies and corporations 11,092 (76 ) 0 0 11,092 (76 ) Mortgage-backed securities - residential 175,183 (1,109 ) 108,782 (3,025 ) 283,965 (4,134 ) Mortgage-backed securities - commercial 132,818 (1,713 ) 72,139 (2,704 ) 204,957 (4,417 ) Collateralized mortgage obligations 164,909 (1,138 ) 101,436 (2,325 ) 266,345 (3,463 ) Obligations of state and other political subdivisions 38,450 (507 ) 21,639 (435 ) 60,089 (942 ) Asset-backed securities 44,941 (200 ) 24,396 (106 ) 69,337 (306 ) Other securities 2,605 (1 ) 7,124 (286 ) 9,729 (287 ) Total $ 570,095 $ (4,745 ) $ 335,516 $ (8,881 ) $ 905,611 $ (13,626 ) December 31, 2016 Less than 12 months 12 months or more Total (Dollars in thousands) Fair Unrealized Fair Unrealized Fair Unrealized U.S. Treasuries $ 97 $ (1 ) $ 0 $ 0 $ 97 $ (1 ) Securities of U.S. Government agencies and corporations 19,917 (150 ) 0 0 19,917 (150 ) Mortgage-backed securities - residential 180,654 (3,621 ) 9,890 (285 ) 190,544 (3,906 ) Mortgage-backed securities - commercial 123,122 (1,200 ) 65,007 (1,443 ) 188,129 (2,643 ) Collateralized mortgage obligations 201,305 (2,882 ) 42,314 (915 ) 243,619 (3,797 ) Obligations of state and other political subdivisions 94,632 (2,710 ) 12,023 (150 ) 106,655 (2,860 ) Asset-backed securities 116,057 (764 ) 92,629 (1,249 ) 208,686 (2,013 ) Other securities 7,746 (237 ) 21,357 (491 ) 29,103 (728 ) Total $ 743,530 $ (11,565 ) $ 243,220 $ (4,533 ) $ 986,750 $ (16,098 )

LOANS (Tables)

LOANS (Tables)	12 Months Ended
	Dec. 31, 2017
LOANS - Carrying Amount of Accretable Yield for Purchased Impaired and Nonimpaired Loans [Abstract]
Commercial and Consumer Credit Exposure by Risk Attribute	Commercial and consumer credit exposure by risk attribute was as follows: As of December 31, 2017 Real Estate (Dollars in thousands) Commercial and industrial Construction Commercial Lease financing Total Pass $ 1,882,464 $ 467,687 $ 2,446,999 $ 88,078 $ 4,885,228 Special Mention 6,226 0 4,436 0 10,662 Substandard 24,053 43 38,656 1,269 64,021 Doubtful 0 0 0 0 0 Total $ 1,912,743 $ 467,730 $ 2,490,091 $ 89,347 $ 4,959,911 Residential real estate Home Equity Installment Credit card Total Performing $ 463,459 $ 489,148 $ 41,331 $ 46,691 $ 1,040,629 Nonperforming 7,932 4,456 255 0 12,643 Total $ 471,391 $ 493,604 $ 41,586 $ 46,691 $ 1,053,272 As of December 31, 2016 Real Estate (Dollars in thousands) Commercial and industrial Construction Commercial Lease financing Total Pass $ 1,725,451 $ 398,155 $ 2,349,662 $ 92,540 $ 4,565,808 Special Mention 18,256 1,258 15,584 108 35,206 Substandard 38,241 21 62,331 460 101,053 Doubtful 0 0 0 0 0 Total $ 1,781,948 $ 399,434 $ 2,427,577 $ 93,108 $ 4,702,067 Residential real estate Home equity Installment Credit card Total Performing $ 491,380 $ 456,314 $ 50,202 $ 43,408 $ 1,041,304 Nonperforming 9,600 4,074 437 0 14,111 Total $ 500,980 $ 460,388 $ 50,639 $ 43,408 $ 1,055,415
Loan Delinquency, including Nonaccrual Loans	Loan delinquency, including nonaccrual loans, was as follows: As of December 31, 2017 (Dollars in thousands) 30 – 59 days past due 60 – 89 days past due > 90 days past due Total past due Current Subtotal Purchased impaired Total > 90 days past due and still accruing Loans Commercial and industrial $ 755 $ 1,657 $ 5,078 $ 7,490 $ 1,901,821 $ 1,909,311 $ 3,432 $ 1,912,743 $ 0 Lease financing 485 0 0 485 88,862 89,347 0 89,347 0 Construction real estate 234 0 0 234 467,216 467,450 280 467,730 0 Commercial real estate 1,716 201 8,777 10,694 2,419,969 2,430,663 59,428 2,490,091 0 Residential real estate 526 811 1,992 3,329 430,500 433,829 37,562 471,391 0 Home equity 2,716 394 1,753 4,863 485,127 489,990 3,614 493,604 0 Installment 179 29 205 413 40,529 40,942 644 41,586 0 Credit card 285 87 62 434 46,257 46,691 0 46,691 62 Total $ 6,896 $ 3,179 $ 17,867 $ 27,942 $ 5,880,281 $ 5,908,223 $ 104,960 $ 6,013,183 $ 62 As of December 31, 2016 (Dollars in thousands) 30 - 59 days past due 60 - 89 days past due > 90 days past due Total past due Current Subtotal Purchased impaired Total > 90 days past due and still accruing Loans Commercial and industrial $ 1,257 $ 208 $ 1,339 $ 2,804 $ 1,773,939 $ 1,776,743 $ 5,205 $ 1,781,948 $ 0 Lease financing 137 0 115 252 92,856 93,108 0 93,108 0 Construction real estate 0 0 0 0 398,877 398,877 557 399,434 0 Commercial real estate 777 134 5,589 6,500 2,339,327 2,345,827 81,750 2,427,577 2,729 Residential real estate 821 37 2,381 3,239 450,631 453,870 47,110 500,980 0 Home equity 195 145 1,776 2,116 456,143 458,259 2,129 460,388 0 Installment 24 1 258 283 49,058 49,341 1,298 50,639 0 Credit card 457 177 142 776 42,632 43,408 0 43,408 142 Total $ 3,668 $ 702 $ 11,600 $ 15,970 $ 5,603,463 $ 5,619,433 $ 138,049 $ 5,757,482 $ 2,871
Loans Restructured During Period	The following table provides information on loan modifications classified as TDRs during the years ended December 31, 2017 , 2016 and 2015 : Years ended December 31, 2017 2016 2015 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial and industrial 7 $ 5,724 $ 5,661 18 $ 3,402 $ 3,508 33 $ 9,035 $ 8,203 Construction real estate 0 0 0 0 0 0 0 0 0 Commercial real estate 8 1,816 1,758 16 5,200 4,752 18 20,249 16,474 Residential real estate 6 416 315 5 840 787 10 1,292 1,238 Home equity 1 39 39 5 165 156 25 2,859 2,221 Installment 0 0 0 3 9 9 10 97 97 Total 22 $ 7,995 $ 7,773 47 $ 9,616 $ 9,212 96 $ 33,532 $ 28,233
Loans Restructured, Modifications	The following table provides information on how TDRs were modified during the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Extended maturities $ 3,261 $ 2,571 $ 12,883 Adjusted interest rates 2,767 0 0 Combination of rate and maturity changes 489 3,046 1,244 Forbearance 1,181 88 260 Other (1) 75 3,507 13,846 Total $ 7,773 $ 9,212 $ 28,233 (1) Other includes covenant modifications and other concessions or combination of concessions that do not consist of interest rate adjustments, forbearance and maturity extensions.
Loan Restructuring, Loans with a Payment Default Within 12 Months of Loan Modification
Nonaccrual, Restructured and Impaired Loans	The following table provides information on impaired loans, excluding purchased impaired loans, as of December 31: (Dollars in thousands) 2017 2016 2015 Impaired loans Nonaccrual loans (1) Commercial and industrial $ 5,229 $ 2,419 $ 8,405 Lease financing 82 195 122 Construction real estate 29 0 0 Commercial real estate 10,616 6,098 9,418 Residential real estate 4,140 5,251 5,027 Home equity 3,743 3,400 4,898 Installment 243 367 127 Total nonaccrual loans 24,082 17,730 27,997 Accruing troubled debt restructurings 17,545 30,240 28,876 Total impaired loans $ 41,627 $ 47,970 $ 56,873 Interest income effect Gross amount of interest that would have been recorded under original terms $ 3,397 $ 2,848 $ 3,595 Interest included in income Nonaccrual loans 535 375 475 Troubled debt restructurings 710 876 682 Total interest included in income 1,245 1,251 1,157 Net impact on interest income $ 2,152 $ 1,597 $ 2,438 Commitments outstanding to borrowers with nonaccrual loans $ 0 $ 0 $ 1 (1) Nonaccrual loans include nonaccrual TDRs of $6.4 million , $5.1 million and $9.3 million as of December 31, 2017 , 2016 and 2015 , respectively.
Investment in Impaired Loans	First Financial's investment in impaired loans, excluding purchased impaired loans, is as follows: December 31, 2017 December 31, 2016 (Dollars in thousands) Current balance Contractual principal balance Related allowance Current balance Contractual Related Loans with no related allowance recorded Commercial and industrial $ 7,162 $ 8,460 $ 0 $ 12,134 $ 12,713 $ 0 Lease financing 82 82 0 195 195 0 Construction real estate 29 60 0 0 0 0 Commercial real estate 18,423 20,837 0 12,232 14,632 0 Residential real estate 6,876 8,145 0 8,412 9,648 0 Home equity 4,356 5,399 0 3,973 5,501 0 Installment 255 422 0 437 603 0 Total 37,183 43,405 0 37,383 43,292 0 Loans with an allowance recorded Commercial and industrial 169 169 169 1,069 1,071 550 Lease financing 0 0 0 0 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 3,119 3,120 448 8,228 8,277 593 Residential real estate 1,056 1,063 160 1,189 1,189 179 Home equity 100 100 2 101 101 2 Installment 0 0 0 0 0 0 Total 4,444 4,452 779 10,587 10,638 1,324 Total Commercial and industrial 7,331 8,629 169 13,203 13,784 550 Lease financing 82 82 0 195 195 0 Construction real estate 29 60 0 0 0 0 Commercial real estate 21,542 23,957 448 20,460 22,909 593 Residential real estate 7,932 9,208 160 9,601 10,837 179 Home equity 4,456 5,499 2 4,074 5,602 2 Installment 255 422 0 437 603 0 Total $ 41,627 $ 47,857 $ 779 $ 47,970 $ 53,930 $ 1,324 Years ended December 31, 2017 2016 2015 (Dollars in thousands) Average balance Interest Average balance Interest income recognized Average Interest Loans with no related allowance recorded Commercial and industrial $ 13,167 $ 280 $ 13,619 $ 309 $ 10,468 $ 258 Lease financing 112 4 150 3 24 0 Construction real estate 601 1 0 0 150 0 Commercial real estate 20,935 563 14,252 357 19,363 344 Residential real estate 7,616 196 7,752 199 8,143 184 Home equity 4,032 99 4,830 86 5,648 82 Installment 332 4 366 7 380 7 Total 46,795 1,147 40,969 961 44,176 875 Loans with an allowance recorded Commercial and industrial 1,204 28 1,098 37 1,409 26 Lease financing 0 0 214 8 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 2,634 40 7,792 211 12,928 213 Residential real estate 1,112 26 1,374 30 1,696 40 Home equity 101 4 101 4 101 3 Installment 0 0 0 0 0 0 Total 5,051 98 10,579 290 16,134 282 Total Commercial and industrial 14,371 308 14,717 346 11,877 284 Lease financing 112 4 364 11 24 0 Construction real estate 601 1 0 0 150 0 Commercial real estate 23,569 603 22,044 568 32,291 557 Residential real estate 8,728 222 9,126 229 9,839 224 Home equity 4,133 103 4,931 90 5,749 85 Installment 332 4 366 7 380 7 Total $ 51,846 $ 1,245 $ 51,548 $ 1,251 $ 60,310 $ 1,157
Changes in Other Real Estate Owned	Changes in OREO were as follows: Years ended December 31, (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 6,284 $ 13,254 $ 22,674 Additions Commercial 1,732 1,850 5,187 Residential 2,387 1,022 3,211 Total additions 4,119 2,872 8,398 Disposals Commercial (5,409 ) (6,993 ) (12,722 ) Residential (1,574 ) (2,363 ) (3,095 ) Total disposals (6,983 ) (9,356 ) (15,817 ) Valuation adjustments Commercial (439 ) (345 ) (1,617 ) Residential (200 ) (141 ) (384 ) Total valuation adjustments (639 ) (486 ) (2,001 ) Balance at end of year $ 2,781 $ 6,284 $ 13,254

ALLOWANCE FOR LOAN AND LEASE 34

ALLOWANCE FOR LOAN AND LEASE LOSSES (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Changes in the Allowance for Loan and Lease Losses for the Previous Three Years	Changes in the ALLL for the three years ended December 31 were as follows: (Dollars in thousands) 2017 2016 2015 Changes in the ALLL, excluding covered/formerly covered loans Balance at beginning of year $ 49,422 $ 43,149 $ 42,820 Provision for loan and lease losses 8,038 9,322 7,926 Loans charged-off (12,712 ) (6,652 ) (11,660 ) Recoveries 4,124 3,603 4,063 Balance at end of year $ 48,872 $ 49,422 $ 43,149 Changes in the ALLL for covered/formerly covered loans Balance at beginning of year $ 8,539 $ 10,249 $ 10,038 Provision for loan and lease losses (4,456 ) 818 1,715 Loans charged-off (951 ) (4,462 ) (8,896 ) Recoveries 2,017 1,934 7,392 Balance at end of year $ 5,149 $ 8,539 $ 10,249 Total changes in the ALLL Balance at beginning of year $ 57,961 $ 53,398 $ 52,858 Provision for loan and lease losses 3,582 10,140 9,641 Loans charged-off (13,663 ) (11,114 ) (20,556 ) Recoveries 6,141 5,537 11,455 Balance at end of year $ 54,021 $ 57,961 $ 53,398
Allowance for Loan and Lease Losses by Classification	Changes in the ALLL by loan category as of December 31 were as follows: 2017 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Provision for loan and lease losses 6,917 (42 ) 207 (7,291 ) 1,695 1,778 (90 ) 408 3,582 Gross charge-offs (10,194 ) 0 (1 ) (1,038 ) (435 ) (913 ) (225 ) (857 ) (13,663 ) Recoveries 1,650 1 89 2,719 215 1,027 234 206 6,141 Total net charge-offs (8,544 ) 1 88 1,681 (220 ) 114 9 (651 ) (7,522 ) Ending allowance for loan and lease losses $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 2016 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 16,995 $ 821 $ 1,810 $ 23,656 $ 4,014 $ 3,943 $ 386 $ 1,773 $ 53,398 Provision for loan and lease losses 3,705 (106 ) 1,280 5,365 (655 ) (175 ) 53 673 10,140 Gross charge-offs (2,630 ) 0 (93 ) (4,983 ) (387 ) (1,445 ) (386 ) (1,190 ) (11,114 ) Recoveries 1,155 1 285 2,502 236 720 335 303 5,537 Total net charge-offs (1,475 ) 1 192 (2,481 ) (151 ) (725 ) (51 ) (887 ) (5,577 ) Ending allowance for loan and lease losses $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 2015 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Allowance for loan and lease losses Balance at beginning of year $ 13,870 $ 435 $ 1,045 $ 27,086 $ 3,753 $ 4,260 $ 407 $ 2,002 $ 52,858 Provision for loan and lease losses 4,809 384 597 1,439 1,234 573 25 580 9,641 Gross charge-offs (5,408 ) 0 (85 ) (10,083 ) (1,531 ) (1,891 ) (509 ) (1,049 ) (20,556 ) Recoveries 3,724 2 253 5,214 558 1,001 463 240 11,455 Total net charge-offs (1,684 ) 2 168 (4,869 ) (973 ) (890 ) (46 ) (809 ) (9,101 ) Ending allowance for loan and lease losses $ 16,995 $ 821 $ 1,810 $ 23,656 $ 4,014 $ 3,943 $ 386 $ 1,773 $ 53,398 The ALLL balance and the recorded investment in loans by portfolio segment and based on impairment method as of December 31 were as follows: December 31, 2017 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home Equity Installment Credit card Total Ending allowance on loans individually evaluated for impairment $ 169 $ 0 $ 0 $ 448 $ 160 $ 2 $ 0 $ 0 $ 779 Ending allowance on loans collectively evaluated for impairment 17,429 675 3,577 20,482 4,523 4,933 307 1,316 53,242 Ending allowance for loan and lease losses $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 Loans and Leases Ending balance of loans individually evaluated for impairment $ 7,331 $ 82 $ 29 $ 21,542 $ 7,932 $ 4,456 $ 255 $ 0 $ 41,627 Ending balance of loans collectively evaluated for impairment 1,905,412 89,265 467,701 2,468,549 463,459 489,148 41,331 46,691 5,971,556 Total loans $ 1,912,743 $ 89,347 $ 467,730 $ 2,490,091 $ 471,391 $ 493,604 $ 41,586 $ 46,691 $ 6,013,183 December 31, 2016 Real Estate (Dollars in thousands) Commercial and industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance on loans individually evaluated for impairment $ 550 $ 0 $ 0 $ 593 $ 179 $ 2 $ 0 $ 0 $ 1,324 Ending allowance on loans collectively evaluated for impairment 18,675 716 3,282 25,947 3,029 3,041 388 1,559 56,637 Ending allowance for loan and lease losses $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Loans and Leases Ending balance of loans individually evaluated for impairment $ 13,203 $ 195 $ 0 $ 20,460 $ 9,601 $ 4,074 $ 437 $ 0 $ 47,970 Ending balance of loans collectively evaluated for impairment 1,768,745 92,913 399,434 2,407,117 491,379 456,314 50,202 43,408 5,709,512 Total loans $ 1,781,948 $ 93,108 $ 399,434 $ 2,427,577 $ 500,980 $ 460,388 $ 50,639 $ 43,408 $ 5,757,482

PREMISES AND EQUIPMENT (Tables)

PREMISES AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	Premises and equipment at December 31 were as follows: (Dollars in thousands) 2017 2016 Land and land improvements $ 41,711 $ 41,112 Buildings 104,576 107,918 Furniture and fixtures 55,165 55,368 Leasehold improvements 19,377 19,544 Construction in progress 1,721 3,791 222,550 227,733 Less: Accumulated depreciation and amortization 97,514 96,154 Total $ 125,036 $ 131,579
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	First Financial's future minimum lease payments for operating leases are as follows: (Dollars in thousands) 2018 $ 6,468 2019 6,212 2020 5,962 2021 5,161 2022 3,112 Thereafter 8,346 Total $ 35,261

GOODWILL AND OTHER INTANGIBLE36

GOODWILL AND OTHER INTANGIBLE ASSETS GOODWILL(Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	Changes in the carrying amount of goodwill for the years ended December 31, 2017 , 2016 and 2015 are shown below. (Dollars in thousands) 2017 2016 2015 Balance at beginning of year $ 204,084 $ 204,084 $ 137,739 Goodwill resulting from business combinations 0 0 66,345 Balance at end of year $ 204,084 $ 204,084 $ 204,084
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	The estimated amortization expense of intangible assets for the next five years is as follows: (Dollars in thousands) Amortization Expense 2018 $ 1,097 2019 1,020 2020 788 2021 636 2022 189

DEPOSITS (Tables)

DEPOSITS (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Maturities of time deposits [Table Text Block]	Scheduled maturities of time deposits for the next five years were as follows: (Dollars in thousands) Total 2018 $ 783,451 2019 315,274 2020 122,165 2021 68,532 2022 27,394 Thereafter 289 Total $ 1,317,105

BORROWINGS (Tables)

BORROWINGS (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Short-term Debt [Table Text Block]	The following is a summary of short-term borrowings for the last three years: 2017 2016 2015 (Dollars in thousands) Amount Rate Amount Rate Amount Rate At December 31, Federal funds purchased and securities sold under agreements to repurchase $ 72,265 0.19 % $ 120,212 0.12 % $ 89,325 0.11 % FHLB borrowings 742,300 1.43 % 687,700 0.66 % 849,100 0.47 % Total $ 814,565 1.32 % $ 807,912 0.58 % $ 938,425 0.44 % Average for the year Federal funds purchased and securities sold under agreements to repurchase $ 69,766 0.19 % $ 89,157 0.05 % $ 73,191 0.07 % FHLB borrowings 760,558 1.05 % 791,259 0.55 % 552,360 0.24 % Other short-term borrowings 41 4.07 % 41 3.56 % 123 3.30 % Total $ 830,365 0.98 % $ 880,457 0.50 % $ 625,674 0.22 % Maximum month-end balances Federal funds purchased and securities sold under agreements to repurchase $ 130,633 $ 122,242 $ 123,374 FHLB borrowings 957,700 1,035,000 849,100 Other short-term borrowings 0 0 15,000
Summary of Long-term Debt [Table Text Block]	The following is a summary of First Financial's long-term debt: 2017 2016 (Dollars in thousands) Amount Average Rate Amount Average Rate Subordinated debt $ 120,000 5.13 % $ 120,000 5.13 % Unamortized debt issuance costs (1,362 ) n/a (1,537 ) n/a FHLB 241 1.09 % 351 1.43 % Capital loan with municipality 775 0.00 % 775 0.00 % Total long-term debt $ 119,654 5.14 % $ 119,589 5.15 %
Schedule of Maturities of Long-term Debt [Table Text Block]	As of December 31, 2017 , First Financial's long-term debt matures as follows: (Dollars in thousands) Long-term debt 2018 $ 15 2019 226 2020 0 2021 0 2022 0 Thereafter 119,413 Total $ 119,654

DERIVATIVES (Tables)

DERIVATIVES (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Derivative Financial Instruments and Balances	The following table details the location and amounts recognized in the Consolidated Balance Sheets for client derivatives: December 31, 2017 December 31, 2016 Estimated fair value Estimated fair value (Dollars in thousands) Balance Sheet Location Notional amount Gain Loss Notional amount Gain Loss Client derivatives Matched interest rate swaps with borrower Accrued interest and other assets and other liabilities $ 837,040 $ 7,153 $ (5,529 ) $ 677,028 $ 8,401 $ (4,158 ) Matched interest rate swaps with counterparty Accrued interest and other liabilities 837,040 5,529 (7,158 ) 677,028 4,158 (8,429 ) Total $ 1,674,080 $ 12,682 $ (12,687 ) $ 1,354,056 $ 12,559 $ (12,587 )
Disclosure by Type of Financial Instrument [Table Text Block]	The following table discloses the gross and net amounts of assets and liabilities recognized in the Consolidated Balance Sheets: December 31, 2017 December 31, 2016 (Dollars in thousands) Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of assets presented in the Consolidated Balance Sheets Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of assets presented in the Consolidated Balance Sheets Client derivatives Matched interest rate swaps $ 12,687 $ 2,279 $ 14,966 $ 12,587 $ (462 ) $ 12,125
Derivative Financial Instruments, Average Remaining Maturity and the Weighted-Average Interest Rates being Paid and Received	The following table details the derivative financial instruments, the average remaining maturities and the weighted-average interest rates being paid and received by First Financial at December 31, 2017 : Weighted-Average Rate (Dollars in thousands) Notional amount Average maturity (years) Fair value Receive Pay Client derivatives Receive fixed, matched interest rate swaps with borrower $ 837,040 5.9 $ 1,624 4.37 % 3.66 % Pay fixed, matched interest rate swaps with counterparty 837,040 5.9 (1,629 ) 3.66 % 4.37 % Total client derivatives $ 1,674,080 5.9 $ (5 ) 4.01 % 4.01 %

RELATED PARTIES TRANSACTIONS (T

RELATED PARTIES TRANSACTIONS (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Schedule of Loans to Related Parties [Table Text Block]	Loans to directors, executive officers, principal holders of First Financial’s common stock and certain related persons were as follows: (Dollars in thousands) 2017 Beginning balance $ 6,930 Additions 3,904 Deductions (961 ) Ending balance $ 9,873 Loans 90 days or more past due $ 0

INCOME TAXES INCOME TAXES (Tabl

INCOME TAXES INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Income tax expense consisted of the following components: (Dollars in thousands) 2017 2016 2015 Current expense Federal $ 22,599 $ 40,537 $ 31,428 State 1,265 1,322 250 Total current expense 23,864 41,859 31,678 Deferred (benefit) expense Federal (4,657 ) 528 3,980 State 169 (182 ) 212 Total deferred (benefit) expense (4,488 ) 346 4,192 Income tax expense $ 19,376 $ 42,205 $ 35,870
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The difference between the federal income tax rates, applied to income before income taxes, and the effective rates were due to the following: (Dollars in thousands) 2017 2016 2015 Income taxes computed at federal statutory rate (35%) on income before income taxes $ 40,657 $ 45,756 $ 38,827 Benefit from tax-exempt income (3,427 ) (2,911 ) (2,815 ) Tax credits (16,806 ) (2,691 ) (1,388 ) Tax rate reduction impact (8,191 ) 0 0 Basis reduction on historic tax credit 4,599 0 0 Tax benefit of equity compensation (1,449 ) (72 ) (35 ) State income taxes, net of federal tax benefit 932 741 301 Affordable housing investments 2,798 1,923 455 Other 263 (541 ) 525 Income tax expense $ 19,376 $ 42,205 $ 35,870
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The major components of the temporary differences that give rise to deferred tax assets and liabilities at December 31, 2017 , and 2016 , were as follows: (Dollars in thousands) 2017 2016 Deferred tax assets Allowance for loan and lease losses $ 12,134 $ 20,955 Deferred compensation 384 627 Postretirement benefits other than pension liability 564 925 Accrued stock-based compensation 932 1,094 Other real estate owned write-downs 97 888 Interest on nonaccrual loans 616 844 Accrued expenses 3,051 5,081 Net unrealized losses on investment securities and derivatives 249 3,141 Other 708 453 Total deferred tax assets 18,735 34,008 Deferred tax liabilities Tax depreciation greater than book depreciation (2,510 ) (5,166 ) FHLB and FRB stock (3,384 ) (5,535 ) Mortgage-servicing rights (343 ) (530 ) Leasing activities (2,792 ) (4,933 ) Prepaid pension (8,888 ) (12,539 ) Intangible assets (11,559 ) (16,611 ) Deferred loan fees and costs (371 ) (1,238 ) Prepaid expenses (210 ) (348 ) Partnership investments (1,230 ) (1,218 ) Fair value adjustments on acquisitions 0 (1,404 ) Other (2,415 ) (852 ) Total deferred tax liabilities (33,702 ) (50,374 ) Total net deferred tax liability $ (14,967 ) $ (16,366 )
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	A progression of unrecognized tax benefits as of December 31, 2017 and 2016 is as follows: (Dollars in thousands) 2017 2016 Balance at beginning of year $ 3,735 $ 0 Additions for tax positions of prior years 0 3,735 Balance at end of year $ 3,735 $ 3,735

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Amounts Recognized in Balance Sheet and Income Statement [Table Text Block]	The following tables set forth information concerning amounts recognized in First Financial's Consolidated Balance Sheets and Consolidated Statements of Income related to the Company's pension plan: December 31, (Dollars in thousands) 2017 2016 Change in benefit obligation Benefit obligation at beginning of year $ 62,729 $ 60,664 Service cost 4,894 5,034 Interest cost 2,325 2,262 Actuarial (gain) loss 6,107 142 Benefits paid, excluding settlement (4,901 ) (5,373 ) Benefit obligation at end of year 71,154 62,729 Change in plan assets Fair value of plan assets at beginning of year 131,011 125,714 Actual return on plan assets 18,239 10,670 Benefits paid, excluding settlement (4,901 ) (5,373 ) Fair value of plan assets at end of year 144,349 131,011 Amounts recognized in the Consolidated Balance Sheets Assets 73,195 68,282 Liabilities 0 0 Net amount recognized $ 73,195 $ 68,282 Amounts recognized in accumulated other comprehensive income (loss) Net actuarial loss $ 33,580 $ 38,278 Net prior service cost (1,921 ) (2,334 ) Deferred tax assets (12,028 ) (13,141 ) Net amount recognized $ 19,631 $ 22,803 Change in accumulated other comprehensive income (loss) $ (3,172 ) $ (1,245 ) Accumulated benefit obligation $ 69,678 $ 61,909
Schedule of Components of Net Periodic Benefit Cost [Table Text Block]	Components of net periodic benefit cost December 31, (Dollars in thousands) 2017 2016 2015 Service cost $ 4,894 $ 5,034 $ 4,807 Interest cost 2,325 2,262 2,120 Expected return on assets (9,358 ) (9,644 ) (9,444 ) Amortization of prior service cost (413 ) (413 ) (413 ) Recognized net actuarial loss 1,924 1,608 1,888 Net periodic benefit (income) cost (628 ) (1,153 ) (1,042 ) Other changes recognized in accumulated other comprehensive income (loss) Net actuarial (gain) loss (2,775 ) (884 ) 11,014 Prior service cost 0 0 0 Amortization of prior service cost 413 413 413 Amortization of gain (1,924 ) (1,608 ) (1,888 ) Total recognized in accumulated other comprehensive income (loss) (4,286 ) (2,079 ) 9,539 Total recognized in net periodic benefit cost and accumulated other comprehensive income (loss) $ (4,914 ) $ (3,232 ) $ 8,497 Amount expected to be recognized in net periodic pension expense in the coming year Amortization of (gain) loss $ 2,090 $ 1,754 $ 1,642 Amortization of prior service credit (413 ) (413 ) (413 )
Schedule of Assumptions Used [Table Text Block]	Pension plan assumptions December 31, 2017 2016 2015 Benefit obligations Discount rate 3.43 % 3.88 % 4.05 % Rate of compensation increase 3.50 % 3.50 % 3.50 % Net periodic benefit cost Discount rate 3.88 % 4.05 % 3.76 % Expected return on plan assets 7.25 % 7.50 % 7.50 % Rate of compensation increase 3.50 % 3.50 % 3.50 %
Schedule of Changes in Fair Value of Plan Assets [Table Text Block]	The fair value of the plan assets as of December 31, 2017 by asset category is shown in the table that follows: Fair Value Measurements (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Asset Category Cash $ 175 $ 175 $ 0 $ 0 U. S. Government agencies 6,853 0 6,853 0 Fixed income mutual funds 69,154 69,154 0 0 Equity mutual funds 68,167 68,167 0 0 Total $ 144,349 $ 137,496 $ 6,853 $ 0 The fair value of the plan assets as of December 31, 2016 by asset category is shown in the table that follows: Fair Value Measurements (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Asset Category Cash $ 190 $ 190 $ 0 $ 0 U. S. Government agencies 6,026 0 6,026 0 Fixed income mutual funds 66,483 66,483 0 0 Equity mutual funds 58,311 58,311 0 0 Total $ 131,010 $ 124,984 $ 6,026 $ 0
Schedule of Expected Benefit Payments [Table Text Block]	The following benefit payments, which reflect expected future service, are expected to be paid: (Dollars in thousands) Retirement Benefits 2018 $ 4,758 2019 4,426 2020 5,417 2021 5,771 2022 5,016 Thereafter 29,825

ACCUMULATED OTHER COMPREHENSI43

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Related Tax Effects Allocated to Other Comprehensive Income and Accumulated Other Comprehensive Income (Loss)	The related tax effects allocated to other comprehensive income and accumulated other comprehensive income (loss) are as follows: December 31, 2017 Total other comprehensive income (loss) Total accumulated other (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 8,447 $ 1,649 $ 6,798 $ (2,431 ) $ 4,367 $ (4,549 ) $ 4,367 $ (182 ) Unrealized gain (loss) on derivatives 810 0 810 (296 ) 514 (1,091 ) 514 (577 ) Retirement obligation 2,775 (1,511 ) 4,286 (1,114 ) 3,172 (22,803 ) 3,172 (19,631 ) Total $ 12,032 $ 138 $ 11,894 $ (3,841 ) $ 8,053 $ (28,443 ) $ 8,053 $ (20,390 ) December 31, 2016 Total other comprehensive income (loss) Total accumulated other (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 751 $ 234 $ 517 $ (133 ) $ 384 $ (4,933 ) $ 384 $ (4,549 ) Unrealized gain (loss) on derivatives 809 0 809 (301 ) 508 (1,599 ) 508 (1,091 ) Retirement obligation 884 (1,195 ) 2,079 (834 ) 1,245 (24,048 ) 1,245 (22,803 ) Total $ 2,444 $ (961 ) $ 3,405 $ (1,268 ) $ 2,137 $ (30,580 ) $ 2,137 $ (28,443 ) December 31, 2015 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclassification Reclassification from Pre-tax Tax-effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ (2,200 ) $ 1,505 $ (3,705 ) $ 1,278 $ (2,427 ) $ (2,506 ) $ (2,427 ) $ (4,933 ) Unrealized gain (loss) on derivatives (1,020 ) 0 (1,020 ) 370 (650 ) (949 ) (650 ) (1,599 ) Retirement obligation (11,014 ) (1,475 ) (9,539 ) 3,395 (6,144 ) (17,904 ) (6,144 ) (24,048 ) Foreign currency translation 50 0 50 0 50 (50 ) 50 0 Total $ (14,184 ) $ 30 $ (14,214 ) $ 5,043 $ (9,171 ) $ (21,409 ) $ (9,171 ) $ (30,580 )
Other Accumulated Comprehensive income reclassified from AOCI [Table Text Block]	The following table details the activity reclassified from accumulated other comprehensive income into income during the period: Amount Reclassified from Accumulated Other Comprehensive Income (1) December 31, (Dollars in thousands) 2017 2016 2015 Affected Line Item in the Consolidated Statements of Income Realized gains and losses on securities available-for-sale $ 1,649 $ 234 $ 1,505 Gains on sales of investments securities Defined benefit pension plan Amortization of prior service cost (2) 413 413 413 Salaries and employee benefits Recognized net actuarial loss (2) (1,924 ) (1,608 ) (1,888 ) Salaries and employee benefits Amortization and settlement charges of defined benefit pension items (1,511 ) (1,195 ) (1,475 ) Total reclassifications for the period, before tax $ 138 $ (961 ) $ 30 (1) Negative amounts are debits to profit/loss. (2) Included in the computation of net periodic pension cost (see Note 15 - Employee Benefit Plans for additional details).

CAPITAL (Tables)

CAPITAL (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]	Actual Minimum capital Required to be Minimum capital (Dollars in thousands) Capital Ratio Capital Ratio Capital Ratio Capital Ratio December 31, 2017 Common equity tier 1 capital to risk-weighted assets Consolidated $ 755,735 10.63 % $ 408,746 5.750 % N/A N/A $ 497,604 7.00 % First Financial Bank 794,251 11.21 % 407,220 5.750 % $ 460,336 6.50 % 495,746 7.00 % Tier 1 capital to risk-weighted assets Consolidated 755,839 10.63 % 515,376 7.250 % N/A N/A 604,233 8.50 % First Financial Bank 794,355 11.22 % 513,452 7.250 % $ 566,567 8.00 % 601,978 8.50 % Total capital to risk-weighted assets Consolidated 929,148 13.07 % 657,548 9.250 % N/A N/A 746,406 10.50 % First Financial Bank 856,363 12.09 % 655,093 9.250 % 708,209 10.00 % 743,619 10.50 % Leverage Consolidated 755,839 8.84 % 342,198 4.00 % N/A N/A 342,198 4.00 % First Financial Bank 794,355 9.29 % 342,113 4.00 % 427,642 5.00 % 342,113 4.00 % Actual Minimum capital Required to be Minimum capital (Dollars in thousands) Capital Ratio Capital Ratio Capital Ratio Capital Ratio December 31, 2016 Common equity tier 1 capital to risk-weighted assets Consolidated $ 703,891 10.46 % $ 344,848 5.125 % N/A N/A $ 471,012 7.00 % First Financial Bank 747,151 11.13 % 344,038 5.125 % $ 436,341 6.50 % 469,906 7.00 % Tier 1 capital to risk-weighted assets Consolidated 703,995 10.46 % 445,779 6.625 % N/A N/A 571,943 8.50 % First Financial Bank 747,255 11.13 % 444,732 6.625 % 537,035 8.00 % 570,600 8.50 % Total capital to risk-weighted assets Consolidated 881,158 13.10 % 580,354 8.625 % N/A N/A 706,517 10.50 % First Financial Bank 813,433 12.12 % 578,991 8.625 % 671,294 10.00 % 704,859 10.50 % Leverage Consolidated 703,995 8.60 % 327,562 4.00 % N/A N/A 327,562 4.00 % First Financial Bank 747,255 9.13 % 327,392 4.00 % 409,240 5.00 % 327,392 4.00 %

STOCK OPTIONS AND AWARDS (Table

STOCK OPTIONS AND AWARDS (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation, Stock Options, Activity [Table Text Block]	Stock option activity for the year ended December 31, 2017 , is summarized as follows: (Dollars in thousands, except share and per share data) Number of shares Weighted average exercise price Weighted average remaining contractual life Aggregate intrinsic value Outstanding at beginning of year 113,307 $ 12.08 Granted 0 0.00 Exercised (101,507 ) 12.13 Forfeited or expired 0 0.00 Outstanding at end of year 11,800 $ 11.64 0.12 $ 174 Exercisable at end of year 11,800 $ 11.64 0.12 $ 174
Schedule of Cash Proceeds Received from Share-based Payment Awards [Table Text Block] (Deprecated 2017-01-31)	First Financial uses treasury shares purchased under the Company's share repurchase program to satisfy share-based exercises. 2017 2016 2015 Total intrinsic value of options exercised $ 1,533 $ 661 $ 492 Cash received from exercises $ 341 $ 801 $ 744 Tax benefit from exercises $ 1,991 $ 1,958 $ 1,488
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]	Activity in restricted stock for the previous three years ended December 31 is summarized as follows: 2017 2016 2015 Number of shares Weighted average grant date fair value Number of shares Weighted average grant date fair value Number of shares Weighted average grant date fair value Nonvested at beginning of year 648,817 $ 17.82 643,641 $ 17.21 494,452 $ 16.43 Granted 234,529 27.36 317,695 18.13 439,674 17.65 Vested (307,825 ) 18.12 (263,713 ) 16.82 (227,905 ) 16.45 Forfeited (107,149 ) 21.18 (48,806 ) 17.37 (62,580 ) 16.58 Nonvested at end of year 468,372 $ 21.63 648,817 $ 17.82 643,641 $ 17.21

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share: (Dollars in thousands, except share and per share data) 2017 2016 2015 Numerator Net income $ 96,787 $ 88,526 $ 75,063 Denominator Basic earnings per common share - weighted average shares 61,529,460 61,206,093 61,062,657 Effect of dilutive securities Employee stock awards 581,329 729,335 670,282 Warrants 60,801 49,994 114,608 Diluted earnings per common share - adjusted weighted average shares 62,171,590 61,985,422 61,847,547 Earnings per share available to common shareholders Basic $ 1.57 $ 1.45 $ 1.23 Diluted $ 1.56 $ 1.43 $ 1.21

FAIR VALUE DISCLOSURES (Tables)

FAIR VALUE DISCLOSURES (Tables)	12 Months Ended
	Dec. 31, 2017
Estimated Fair Values of Financial Instruments	The estimated fair values of First Financial's financial instruments not measured at fair value on a recurring or nonrecurring basis in the consolidated financial statements were as follows: Carrying Estimated fair value (Dollars in thousands) value Total Level 1 Level 2 Level 3 December 31, 2017 Financial assets Cash and short-term investments $ 184,624 $ 184,624 $ 184,624 $ 0 $ 0 Investment securities held-to-maturity 654,008 653,101 0 653,101 0 Other investments 53,140 N/A N/A N/A N/A Loans held for sale 11,502 11,502 0 11,502 0 Loans and leases, net of ALLL 5,959,162 6,006,656 0 0 6,006,656 Accrued interest receivable 24,496 24,496 0 8,265 16,231 Financial liabilities Deposits Noninterest-bearing $ 1,662,058 $ 1,662,058 $ 0 $ 1,662,058 $ 0 Interest-bearing demand 1,453,463 1,453,463 0 1,453,463 0 Savings 2,462,420 2,462,420 0 2,462,420 0 Time 1,317,105 1,306,674 0 1,306,674 0 Total deposits 6,895,046 6,884,615 0 6,884,615 0 Short-term borrowings 814,565 814,565 814,565 0 0 Long-term debt 119,654 117,908 0 117,908 0 Accrued interest payable 5,104 5,104 204 4,900 0 Carrying Estimated Fair Value (Dollars in thousands) Value Total Level 1 Level 2 Level 3 December 31, 2016 Financial assets Cash and short-term investments $ 204,048 $ 204,048 $ 204,048 $ 0 $ 0 Investment securities held-to-maturity 763,254 763,575 0 763,575 0 Other investments 51,077 N/A N/A N/A N/A Loans held for sale 13,135 13,135 0 13,135 0 Loans and leases, net of ALLL 5,699,521 5,754,845 0 0 5,754,845 Accrued interest receivable 18,503 18,503 0 5,705 12,798 Financial liabilities Deposits Noninterest-bearing $ 1,547,985 $ 1,547,985 $ 0 $ 1,547,985 $ 0 Interest-bearing demand 1,513,771 1,513,771 0 1,513,771 0 Savings 2,142,189 2,142,189 0 2,142,189 0 Time 1,321,843 1,316,333 0 1,316,333 0 Total deposits 6,525,788 6,520,278 0 6,520,278 0 Short-term borrowings 807,912 807,912 807,912 0 0 Long-term debt 119,589 117,878 0 117,878 0 Accrued interest payable 5,049 5,049 410 4,639 0
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table summarizes the financial assets and liabilities measured at fair value on a recurring basis: Fair Value Measurements Using Assets/Liabilities (Dollars in thousands) Level 1 Level 2 Level 3 at Fair Value December 31, 2017 Assets Derivatives $ 0 $ 12,757 $ 0 $ 12,757 Investment securities available-for-sale 2,969 1,346,439 0 1,349,408 Total $ 2,969 $ 1,359,196 $ 0 $ 1,362,165 Liabilities Derivatives $ 0 $ 12,755 $ 0 $ 12,755 Fair Value Measurements Using Assets/Liabilities (Dollars in thousands) Level 1 Level 2 Level 3 at Fair Value December 31, 2016 Assets Derivatives $ 0 $ 12,922 $ 0 $ 12,922 Investment securities available-for-sale 8,711 1,031,159 0 1,039,870 Total $ 8,711 $ 1,044,081 $ 0 $ 1,052,792 Liabilities Derivatives $ 0 $ 12,725 $ 0 $ 12,725
Summary of Financial Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis	The following table summarizes financial assets and liabilities measured at fair value on a nonrecurring basis: Fair Value Measurements Using (Dollars in thousands) Level 1 Level 2 Level 3 December 31, 2017 Assets Impaired loans $ 0 $ 0 $ 2,671 OREO 0 0 1,086 Fair Value Measurements Using (Dollars in thousands) Level 1 Level 2 Level 3 December 31, 2016 Assets Impaired loans $ 0 $ 0 $ 8,154 OREO 0 0 3,921

Pending Business Combination (T

Pending Business Combination (Tables)	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Business Acquisition, Pro Forma Information	Pro forma information for the periods ended June 30, 2017 and December 31, 2016 was as follows: For the six For the year months ended ended June 30, 2017 December 31, 2016 (Dollars in thousands, except per share data) (Unaudited) (Unaudited) Pro Forma Condensed Combined Income Statement Information Net interest income $ 204,518 $ 387,725 Provision for loan and lease losses 834 10,140 Income before income taxes 92,591 170,132 Net income 65,884 119,661 As of (Unaudited) Pro Forma Condensed Combined Balance Sheet Information Loans and leases, net $ 8,818,392 Total assets 13,806,092 Deposits 9,987,298 Total shareholders' equity 1,913,682

FIRST FINANCIAL BANCORP. (PAR49

FIRST FINANCIAL BANCORP. (PARENT COMPANY ONLY) FINANCIAL INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule of Condensed Balance Sheet	Balance Sheets December 31, (Dollars in thousands) 2017 2016 Assets Cash $ 57,719 $ 59,285 Investment securities, available for sale 442 386 Subordinated notes from subsidiaries 7,500 7,500 Investment in subsidiaries Commercial banks 970,290 909,798 Total investment in subsidiaries 970,290 909,798 Premises and equipment 1,378 1,395 Other assets 26,778 19,487 Total assets $ 1,064,107 $ 997,851 Liabilities Subordinated debentures $ 118,638 $ 118,463 Dividends payable 10,965 10,386 Other liabilities 3,840 3,778 Total liabilities 133,443 132,627 Shareholders’ equity 930,664 865,224 Total liabilities and shareholders’ equity $ 1,064,107 $ 997,851
Schedule of Condensed Income Statement	Statements of Income Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Income Interest income $ 6 $ 48 $ 81 Noninterest income 86 2,596 253 Dividends from subsidiaries 54,600 52,700 17,250 Total income 54,692 55,344 17,584 Expenses Interest expense 6,152 6,151 2,157 Salaries and employee benefits 5,519 5,445 4,224 Miscellaneous professional services 970 711 723 Other 4,819 4,841 5,564 Total expenses 17,460 17,148 12,668 Income before income taxes and equity in undistributed net earnings of subsidiaries 37,232 38,196 4,916 Income tax benefit (7,080 ) (5,302 ) (4,563 ) Equity in undistributed earnings (loss) of subsidiaries 52,475 45,028 65,584 Net income $ 96,787 $ 88,526 $ 75,063
Schedule of Condensed Cash Flow Statement	Statements of Cash Flows Years Ended December 31, (Dollars in thousands) 2017 2016 2015 Operating activities Net income $ 96,787 $ 88,526 $ 75,063 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed (earnings) loss of subsidiaries (52,475 ) (45,028 ) (65,584 ) Depreciation and amortization 193 192 78 Stock-based compensation expense 5,446 5,354 4,049 Deferred income taxes (360 ) 584 (85 ) (Decrease) increase in dividends payable 579 135 2 (Decrease) increase in other liabilities (889 ) (389 ) 1,965 Decrease (increase) in other assets (6,951 ) (9,065 ) 1,459 Net cash provided by (used in) operating activities 42,330 40,309 16,947 Investing activities Capital contributions to subsidiaries 0 (53,000 ) (40,000 ) Proceeds from calls and maturities of investment securities 0 5,978 87 Purchases of investment securities 0 (333 ) (412 ) Net cash provided by (used in) investing activities 0 (47,355 ) (40,325 ) Financing activities Proceeds from long-term borrowings 0 0 120,000 Cash dividends paid on common stock (41,178 ) (39,125 ) (39,070 ) Treasury stock purchase 0 0 (4,498 ) Proceeds from exercise of stock options, net of shares purchased 341 801 744 Excess tax benefit on share-based compensation 0 264 146 Other (3,059 ) (1,681 ) (3,064 ) Net cash provided by (used in) financing activities (43,896 ) (39,741 ) 74,258 Net increase (decrease) in cash (1,566 ) (46,787 ) 50,880 Cash at beginning of year 59,285 106,072 55,192 Cash at end of year $ 57,719 $ 59,285 $ 106,072

SUMMARY OF SIGNIFICANT ACCOUN50

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance threshold for impaired and non-impaired commercial loans	$ 250,000
Loans, Federal Deposit Insurance Corporation Reimbursement Percentage on Losses Below Threshold	80.00%
Loans, Federal Deposit Insurance Corporation Reimbursement Percentage on Losses Above Threshold	95.00%
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum	$ 250,000

SUMMARY OF SIGNIFICANT ACCOUN51

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Premises and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	20 years
Minimum | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Minimum | Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	3 years
Minimum | Software, Hardware, and Data Handling Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	3 years
Maximum | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	40 years
Maximum | Furniture, Fixtures, and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Maximum | Software, Hardware, and Data Handling Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life, Minimum	5 years

RECENTLY ADOPTED AND ISSUED A52

RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Recently Adopted and Issued Accounting Standards [Abstract]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 1.6
Reclassification from AOCI, Current Period, Tax	$ 4.9

RESTRICTIONS ON CASH AND DIVI53

RESTRICTIONS ON CASH AND DIVIDENDS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restrictions on Subsidiary Dividends, Loans or Advances [Line Items]
Average Restriction on Cash and Due From Bank Accounts	$ 66.7	$ 58.9
Subsidiaries [Member]
Restrictions on Subsidiary Dividends, Loans or Advances [Line Items]
Retained Earnings, Unappropriated	546.5
Amount Available for Dividend Distribution without Affecting Capital Adequacy Requirements	$ 163.1

INVESTMENT SECURITIES INVESTMEN

INVESTMENT SECURITIES INVESTMENTS - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Gain (Loss) on Investments [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 190,000	$ 207,000
Available-for-sale Securities, Gross Realized Gains	1,800	1,200
Available-for-sale Securities, Gross Realized Losses	200	1,000
Proceeds from Sale of Held-to-maturity Securities	0	4,862	$ 0
Pledged Financial Instruments, Not Separately Reported, Securities	$ 819,400	$ 959,783
NumberOfSecuritiesInSecurityPortfolio	775	706
NumberOfSecuritiesInUnrealizedLossPosition	237	255

INVESTMENTS - Summary of Held-T

INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Amortized cost	$ 654,008	$ 763,254
Held To Maturity Gross Unrealized Gain Accumulated In Investments	5,572	6,236
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	6,479	5,915
Held-to-Maturity Market Value	653,101	763,575
Amortized Cost	1,348,227	1,045,337
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	8,328	4,716
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	7,147	10,183
Investment securities, available for sale	1,349,408	1,039,870
Pledged Financial Instruments, Not Separately Reported, Securities	819,400	959,783
U.S. Treasuries
Investment Holdings [Line Items]
Amortized cost	0	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0	0
Held-to-Maturity Market Value	0	0
Amortized Cost	98	98
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	1	1
Investment securities, available for sale	97	97
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Amortized cost	11,168	13,011
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	76	110
Held-to-Maturity Market Value	11,092	12,901
Amortized Cost	15,695	7,056
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	220	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	40
Investment securities, available for sale	15,915	7,016
Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	162,093	205,522
Held To Maturity Gross Unrealized Gain Accumulated In Investments	2,042	1,740
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	1,535	1,166
Held-to-Maturity Market Value	162,600	206,096
Amortized Cost	290,793	184,960
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	849	1,175
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	2,599	2,740
Investment securities, available for sale	289,043	183,395
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	255,027	278,728
Held To Maturity Gross Unrealized Gain Accumulated In Investments	1,372	3,254
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	3,000	1,817
Held-to-Maturity Market Value	253,399	280,165
Amortized Cost	150,356	154,239
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	164	188
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	1,417	826
Investment securities, available for sale	149,103	153,601
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	143,545	195,408
Held To Maturity Gross Unrealized Gain Accumulated In Investments	354	1,125
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	1,602	1,476
Held-to-Maturity Market Value	142,297	195,057
Amortized Cost	306,095	232,701
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,158	634
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	1,861	2,321
Investment securities, available for sale	305,392	231,014
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Amortized cost	82,175	70,585
Held To Maturity Gross Unrealized Gain Accumulated In Investments	1,804	117
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	266	1,346
Held-to-Maturity Market Value	83,713	69,356
Amortized Cost	124,269	96,934
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,162	1,461
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	676	1,514
Investment securities, available for sale	125,755	96,881
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	0	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0	0
Held-to-Maturity Market Value	0	0
Amortized Cost	377,655	322,708
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,628	517
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	306	2,013
Investment securities, available for sale	378,977	321,212
Other securities
Investment Holdings [Line Items]
Amortized cost	0	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0	0
Held-to-Maturity Market Value	0	0
Amortized Cost	83,266	46,641
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,147	741
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	287	728
Investment securities, available for sale	$ 85,126	$ 46,654

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Held-to-Maturity Amortized Cost
Amortized cost	$ 654,008	$ 763,254
Held-to-Maturity Market Value
Held-to-Maturity Market Value	653,101	763,575
Available-for-Sale Amortized Cost
Amortized Cost	1,348,227	1,045,337
Available-for-Sale Market Value
Investment securities, available for sale	1,349,408	1,039,870
One Year or Less [Member]
Held-to-Maturity Amortized Cost
Amortized cost	165
Held-to-Maturity Market Value
Held-to-Maturity Market Value	165
Available-for-Sale Amortized Cost
Amortized Cost	2,422
Available-for-Sale Market Value
Investment securities, available for sale	2,423
After One Year Through Five Years [Member]
Held-to-Maturity Amortized Cost
Amortized cost	4,492
Held-to-Maturity Market Value
Held-to-Maturity Market Value	4,494
Available-for-Sale Amortized Cost
Amortized Cost	37,064
Available-for-Sale Market Value
Investment securities, available for sale	37,149
After Five Years Through Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized cost	2,500
Held-to-Maturity Market Value
Held-to-Maturity Market Value	2,723
Available-for-Sale Amortized Cost
Amortized Cost	82,404
Available-for-Sale Market Value
Investment securities, available for sale	84,168
After Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized cost	86,186
Held-to-Maturity Market Value
Held-to-Maturity Market Value	87,423
Available-for-Sale Amortized Cost
Amortized Cost	101,438
Available-for-Sale Market Value
Investment securities, available for sale	103,153
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized cost	143,545	195,408
Held-to-Maturity Market Value
Held-to-Maturity Market Value	142,297	195,057
Available-for-Sale Amortized Cost
Amortized Cost	306,095	232,701
Available-for-Sale Market Value
Investment securities, available for sale	305,392	231,014
Asset-backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized cost	0	0
Held-to-Maturity Market Value
Held-to-Maturity Market Value	0	0
Available-for-Sale Amortized Cost
Amortized Cost	377,655	322,708
Available-for-Sale Market Value
Investment securities, available for sale	$ 378,977	$ 321,212

INVESTMENTS - Age of Gross Unre

INVESTMENTS - Age of Gross Unrealized Losses and Associated Fair Value by Investment Category (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Proceeds from Sale of Held-to-maturity Securities	$ 0	$ 4,862	$ 0
Less than 12 Months Fair Value	570,095	743,530
Less than 12 Months Unrealized Loss	(4,745)	(11,565)
12 Months or More Fair Value	335,516	243,220
12 Months or More Unrealized Loss	(8,881)	(4,533)
Total Fair Value	905,611	986,750
Total Unrealized Loss	(13,626)	(16,098)
U.S. Treasuries
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	97	97
Less than 12 Months Unrealized Loss	(1)	(1)
12 Months or More Fair Value	0	0
12 Months or More Unrealized Loss	0	0
Total Fair Value	97	97
Total Unrealized Loss	(1)	(1)
Securities of U.S. government agencies and corporations
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	11,092	19,917
Less than 12 Months Unrealized Loss	(76)	(150)
12 Months or More Fair Value	0	0
12 Months or More Unrealized Loss	0	0
Total Fair Value	11,092	19,917
Total Unrealized Loss	(76)	(150)
Residential Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	175,183	180,654
Less than 12 Months Unrealized Loss	(1,109)	(3,621)
12 Months or More Fair Value	108,782	9,890
12 Months or More Unrealized Loss	(3,025)	(285)
Total Fair Value	283,965	190,544
Total Unrealized Loss	(4,134)	(3,906)
Commercial Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	132,818	123,122
Less than 12 Months Unrealized Loss	(1,713)	(1,200)
12 Months or More Fair Value	72,139	65,007
12 Months or More Unrealized Loss	(2,704)	(1,443)
Total Fair Value	204,957	188,129
Total Unrealized Loss	(4,417)	(2,643)
Collateralized Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	164,909	201,305
Less than 12 Months Unrealized Loss	(1,138)	(2,882)
12 Months or More Fair Value	101,436	42,314
12 Months or More Unrealized Loss	(2,325)	(915)
Total Fair Value	266,345	243,619
Total Unrealized Loss	(3,463)	(3,797)
Obligations of state and other political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	38,450	94,632
Less than 12 Months Unrealized Loss	(507)	(2,710)
12 Months or More Fair Value	21,639	12,023
12 Months or More Unrealized Loss	(435)	(150)
Total Fair Value	60,089	106,655
Total Unrealized Loss	(942)	(2,860)
Asset-backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	44,941	116,057
Less than 12 Months Unrealized Loss	(200)	(764)
12 Months or More Fair Value	24,396	92,629
12 Months or More Unrealized Loss	(106)	(1,249)
Total Fair Value	69,337	208,686
Total Unrealized Loss	(306)	(2,013)
Other securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	2,605	7,746
Less than 12 Months Unrealized Loss	(1)	(237)
12 Months or More Fair Value	7,124	21,357
12 Months or More Unrealized Loss	(286)	(491)
Total Fair Value	9,729	29,103
Total Unrealized Loss	$ (287)	$ (728)

LOANS - Additional Information

LOANS - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)loans	Dec. 31, 2016USD ($)loans	Dec. 31, 2015USD ($)loans	Dec. 31, 2014USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Indemnification valuation adjustment	$ (5,100,000)
Accruing TDRs performing in accordance with restructured terms for more than one year	17,200,000	$ 22,600,000	$ 10,300,000
Restructured Loans, Accrual Status	17,500,000	30,200,000	28,900,000
Purchased impaired loans, carrying balance	$ 104,960,000	138,049,000
Loans, Federal Deposit Insurance Corporation Reimbursement Percentage on Losses Below Threshold	80.00%
Loans, Federal Deposit Insurance Corporation Reimbursement Percentage on Losses Above Threshold	95.00%
Restructured Loans, Nonaccrual Status	$ 6,400,000	5,100,000	9,300,000
Restructured Loans, Allowance for Loan and Lease Losses Included in Reserves	1,300,000	1,900,000	6,300,000
Gain (loss) on sale of other real estate owned	(642,000)	1,212,000	(1,861,000)
Real Estate Acquired Through Foreclosure	2,781,000	6,284,000	13,254,000	$ 22,674,000
Loans and Leases Receivable, Impaired, Commitment to Lend		900,000	1,800,000
Restructured Loans, Portion Determined to be Uncollectible	$ 300,000	$ 500,000	$ 2,700,000
Number of Restructured Loans | loans	214	247	271
Total restructured loans	$ 23,900,000	$ 35,400,000	$ 38,200,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum	$ 250,000

LOANS - Commercial and Consumer

LOANS - Commercial and Consumer Credit Exposure by Risk Attribute (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Commercial and industrial	$ 1,912,743	$ 1,781,948
Real Estate - Construction	467,730	399,434
Real Estate - Commercial	2,490,091	2,427,577
Lease financing	89,347	93,108
Total Commercial	4,959,911	4,702,067
Pass
Financing Receivable, Recorded Investment [Line Items]
Commercial and industrial	1,882,464	1,725,451
Real Estate - Construction	467,687	398,155
Real Estate - Commercial	2,446,999	2,349,662
Lease financing	88,078	92,540
Total Commercial	4,885,228	4,565,808
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Commercial and industrial	6,226	18,256
Real Estate - Construction	0	1,258
Real Estate - Commercial	4,436	15,584
Lease financing	0	108
Total Commercial	10,662	35,206
Substandard
Financing Receivable, Recorded Investment [Line Items]
Commercial and industrial	24,053	38,241
Real Estate - Construction	43	21
Real Estate - Commercial	38,656	62,331
Lease financing	1,269	460
Total Commercial	64,021	101,053
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Commercial and industrial	0	0
Real Estate - Construction	0	0
Real Estate - Commercial	0	0
Lease financing	0	0
Total Commercial	0	0
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	471,391	500,980
Residential Real Estate [Member] | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	463,459	491,380
Residential Real Estate [Member] | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	7,932	9,600
Home Equity Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	493,604	460,388
Home Equity Loan [Member] | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	489,148	456,314
Home Equity Loan [Member] | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	4,456	4,074
Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	41,586	50,639
Consumer Loan [Member] | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	41,331	50,202
Consumer Loan [Member] | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	255	437
Credit card
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	46,691	43,408
Credit card | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	46,691	43,408
Credit card | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	0	0
Installment
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	1,053,272	1,055,415
Installment | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	1,040,629	1,041,304
Installment | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 12,643	$ 14,111

LOANS - Loan Delinquency, inclu

LOANS - Loan Delinquency, including Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	$ 27,942	$ 15,970
Current	5,880,281	5,603,463
Loans and Leases Receivable, Gross	5,908,223	5,619,433
Purchased impaired loans, carrying balance	104,960	138,049
Total loans and leases	6,013,183	5,757,482
Greater than 90 days past due and still accruing	62	2,871
30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	6,896	3,668
60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	3,179	702
Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	17,867	11,600
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	7,490	2,804
Current	1,901,821	1,773,939
Loans and Leases Receivable, Gross	1,909,311	1,776,743
Purchased impaired loans, carrying balance	3,432	5,205
Total loans and leases	1,912,743	1,781,948
Greater than 90 days past due and still accruing	0	0
Commercial | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	755	1,257
Commercial | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	1,657	208
Commercial | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	5,078	1,339
Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	485	252
Current	88,862	92,856
Loans and Leases Receivable, Gross	89,347	93,108
Purchased impaired loans, carrying balance	0	0
Total loans and leases	89,347	93,108
Greater than 90 days past due and still accruing	0	0
Lease financing | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	485	137
Lease financing | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	0	0
Lease financing | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	0	115
Construction real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	234	0
Current	467,216	398,877
Loans and Leases Receivable, Gross	467,450	398,877
Purchased impaired loans, carrying balance	280	557
Total loans and leases	467,730	399,434
Greater than 90 days past due and still accruing	0	0
Construction real estate | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	234	0
Construction real estate | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	0	0
Construction real estate | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	0	0
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	10,694	6,500
Current	2,419,969	2,339,327
Loans and Leases Receivable, Gross	2,430,663	2,345,827
Purchased impaired loans, carrying balance	59,428	81,750
Total loans and leases	2,490,091	2,427,577
Greater than 90 days past due and still accruing	0	2,729
Commercial real estate | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	1,716	777
Commercial real estate | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	201	134
Commercial real estate | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	8,777	5,589
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	3,329	3,239
Current	430,500	450,631
Loans and Leases Receivable, Gross	433,829	453,870
Purchased impaired loans, carrying balance	37,562	47,110
Total loans and leases	471,391	500,980
Greater than 90 days past due and still accruing	0	0
Residential real estate | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	526	821
Residential real estate | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	811	37
Residential real estate | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	1,992	2,381
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	4,863	2,116
Current	485,127	456,143
Loans and Leases Receivable, Gross	489,990	458,259
Purchased impaired loans, carrying balance	3,614	2,129
Total loans and leases	493,604	460,388
Greater than 90 days past due and still accruing	0	0
Home equity | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	2,716	195
Home equity | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	394	145
Home equity | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	1,753	1,776
Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	413	283
Current	40,529	49,058
Loans and Leases Receivable, Gross	40,942	49,341
Purchased impaired loans, carrying balance	644	1,298
Total loans and leases	41,586	50,639
Greater than 90 days past due and still accruing	0	0
Installment | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	179	24
Installment | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	29	1
Installment | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	205	258
Credit card
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	434	776
Current	46,257	42,632
Loans and Leases Receivable, Gross	46,691	43,408
Purchased impaired loans, carrying balance	0	0
Total loans and leases	46,691	43,408
Greater than 90 days past due and still accruing	62	142
Credit card | 30 to 59 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	285	457
Credit card | 60 to 89 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	87	177
Credit card | Greater than 90 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, Past Due	$ 62	$ 142

LOANS - Restructured Loans (Det

LOANS - Restructured Loans (Details)	12 Months Ended
	Dec. 31, 2017USD ($)loansd	Dec. 31, 2016USD ($)loans	Dec. 31, 2015USD ($)loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
FDIC indemnification asset	$ 1,900,000	$ 12,000,000
Extended Maturities	3,261,000	2,571,000	$ 12,883,000
Adjusted Interest Rates	2,767,000	0	0
Combined Rate And Maturity	489,000	3,046,000	1,244,000
Forebearance Agreements	1,181,000	88,000	260,000
Other	75,000	3,507,000	13,846,000
Total	$ 7,773,000	$ 9,212,000	$ 28,233,000
Number of Restructured Loans | loans	214	247	271
Restructured loans, Number of Loans | loans	22	47	96
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 7,995,000	$ 9,616,000	$ 33,532,000
Restructured loans, Period End Balance	$ 7,773,000	$ 9,212,000	$ 28,233,000
Restructured loans with payment default within 12 months of modification, Number of Loans | loans	1	4	10
Restructured loans with payment default within 12 months of modification, Period End Balance	$ 1,500,000	$ 300,000	$ 1,600,000
Total restructured loans	23,900,000	35,400,000	38,200,000
Restructured Loans, Accrual Status	17,500,000	30,200,000	28,900,000
Restructured Loans, Nonaccrual Status	6,400,000	5,100,000	9,300,000
Loans and Leases Receivable, Impaired, Commitment to Lend		900,000	1,800,000
Restructured Loans, Allowance for Loan and Lease Losses Included in Reserves	1,300,000	1,900,000	6,300,000
Accruing TDRs performing in accordance with restructured terms for more than one year	$ 17,200,000	$ 22,600,000	$ 10,300,000
Restructured loans performance threshold (days) | d	90
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum	$ 250,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	7	18	33
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 5,724,000	$ 3,402,000	$ 9,035,000
Restructured loans, Period End Balance	$ 5,661,000	$ 3,508,000	$ 8,203,000
Construction real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0	$ 0
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	8	16	18
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 1,816,000	$ 5,200,000	$ 20,249,000
Restructured loans, Period End Balance	$ 1,758,000	$ 4,752,000	$ 16,474,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	6	5	10
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 416,000	$ 840,000	$ 1,292,000
Restructured loans, Period End Balance	315,000	$ 787,000	$ 1,238,000
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum	$ 250,000
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	1	5	25
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 39,000	$ 165,000	$ 2,859,000
Restructured loans, Period End Balance	$ 39,000	$ 156,000	$ 2,221,000
Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	3	10
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 9,000	$ 97,000
Restructured loans, Period End Balance	$ 0	$ 9,000	$ 97,000

LOANS - Nonaccrual, Restructure

LOANS - Nonaccrual, Restructured and Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	$ 24,082	$ 17,730	$ 27,997
Restructured loans - accrual status	17,500	30,200	28,900
Total impaired loans	41,627	47,970	56,873
Interest income effect
Gross amount of interest that would have been recorded under original terms	3,397	2,848	3,595
Interest included in income
Nonaccrual loans	535	375	475
Restructured loans	710	876	682
Impaired Financing Receivable, Interest Income, Accrual Method	1,245	1,251	1,157
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	2,152	1,597	2,438
Loans and Leases Receivable-Nonaccrual, future commitment to lend	0	0	1
Restructured loans - nonaccrual status	6,400	5,100	9,300
Commercial
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	5,229	2,419	8,405
Total impaired loans	7,331	13,203
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	308	346	284
Lease financing
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	82	195	122
Total impaired loans	82	195
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	4	11	0
Construction real estate
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	29	0	0
Total impaired loans	29	0
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	1	0	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	10,616	6,098	9,418
Total impaired loans	21,542	20,460
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	603	568	557
Residential real estate
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	4,140	5,251	5,027
Total impaired loans	7,932	9,601
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	222	229	224
Home equity
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	3,743	3,400	4,898
Total impaired loans	4,456	4,074
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	103	90	85
Installment
Financing Receivable, Modifications [Line Items]
Nonaccrual loans	243	367	127
Total impaired loans	255	437
Interest included in income
Impaired Financing Receivable, Interest Income, Accrual Method	$ 4	$ 7	$ 7

LOANS - Investment in Impaired

LOANS - Investment in Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Current balance	$ 41,627	$ 47,970	$ 56,873
Contractual Principal Balance	47,857	53,930
Allowance for loan and lease losses	779	1,324
Average Recorded Investment	51,846	51,548	60,310
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1,147	961
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	98	290
Total interest included in income	1,245	1,251	1,157
Commercial
Financing Receivable, Impaired [Line Items]
Current balance	7,331	13,203
Contractual Principal Balance	8,629	13,784
Allowance for loan and lease losses	169	550
Average Recorded Investment	14,371	14,717	11,877
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	280	309
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	28	37	26
Total interest included in income	308	346	284
Lease financing
Financing Receivable, Impaired [Line Items]
Current balance	82	195
Contractual Principal Balance	82	195
Allowance for loan and lease losses	0	0
Average Recorded Investment	112	364	24
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	4	3
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	8	0
Total interest included in income	4	11	0
Construction real estate
Financing Receivable, Impaired [Line Items]
Current balance	29	0
Contractual Principal Balance	60	0
Allowance for loan and lease losses	0	0
Average Recorded Investment	601	0	150
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0
Total interest included in income	1	0	0
Commercial real estate
Financing Receivable, Impaired [Line Items]
Current balance	21,542	20,460
Contractual Principal Balance	23,957	22,909
Allowance for loan and lease losses	448	593
Average Recorded Investment	23,569	22,044	32,291
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	563	357
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	40	211	213
Total interest included in income	603	568	557
Residential real estate
Financing Receivable, Impaired [Line Items]
Current balance	7,932	9,601
Contractual Principal Balance	9,208	10,837
Allowance for loan and lease losses	160	179
Average Recorded Investment	8,728	9,126	9,839
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	196	199
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	26	30	40
Total interest included in income	222	229	224
Home equity
Financing Receivable, Impaired [Line Items]
Current balance	4,456	4,074
Contractual Principal Balance	5,499	5,602
Allowance for loan and lease losses	2	2
Average Recorded Investment	4,133	4,931	5,749
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	99	86
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	4	4	3
Total interest included in income	103	90	85
Installment
Financing Receivable, Impaired [Line Items]
Current balance	255	437
Contractual Principal Balance	422	603
Allowance for loan and lease losses	0	0
Average Recorded Investment	332	366	380
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	4	7
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0
Total interest included in income	4	7	7
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Current balance	4,444	10,587
Contractual Principal Balance	4,452	10,638
Allowance for loan and lease losses	779	1,324
Average Recorded Investment	5,051	10,579	16,134
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method			282
Loans with no related allowance recorded [member]
Financing Receivable, Impaired [Line Items]
Current balance	37,183	37,383
Contractual Principal Balance	43,405	43,292
Allowance for loan and lease losses	0	0
Average Recorded Investment	46,795	40,969	44,176
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			875
Loans with no related allowance recorded [member] | Commercial
Financing Receivable, Impaired [Line Items]
Current balance	7,162	12,134
Contractual Principal Balance	8,460	12,713
Allowance for loan and lease losses	0	0
Average Recorded Investment	13,167	13,619	10,468
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			258
Loans with no related allowance recorded [member] | Lease financing
Financing Receivable, Impaired [Line Items]
Current balance	82	195
Contractual Principal Balance	82	195
Allowance for loan and lease losses	0	0
Average Recorded Investment	112	150	24
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			0
Loans with no related allowance recorded [member] | Construction real estate
Financing Receivable, Impaired [Line Items]
Current balance	29	0
Contractual Principal Balance	60	0
Allowance for loan and lease losses	0	0
Average Recorded Investment	601	0	150
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			0
Loans with no related allowance recorded [member] | Commercial real estate
Financing Receivable, Impaired [Line Items]
Current balance	18,423	12,232
Contractual Principal Balance	20,837	14,632
Allowance for loan and lease losses	0	0
Average Recorded Investment	20,935	14,252	19,363
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			344
Loans with no related allowance recorded [member] | Residential real estate
Financing Receivable, Impaired [Line Items]
Current balance	6,876	8,412
Contractual Principal Balance	8,145	9,648
Allowance for loan and lease losses	0	0
Average Recorded Investment	7,616	7,752	8,143
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			184
Loans with no related allowance recorded [member] | Home equity
Financing Receivable, Impaired [Line Items]
Current balance	4,356	3,973
Contractual Principal Balance	5,399	5,501
Allowance for loan and lease losses	0	0
Average Recorded Investment	4,032	4,830	5,648
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			82
Loans with no related allowance recorded [member] | Installment
Financing Receivable, Impaired [Line Items]
Current balance	255	437
Contractual Principal Balance	422	603
Allowance for loan and lease losses	0	0
Average Recorded Investment	332	366	380
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method			7
Impaired Financing Receivables With Related Allowance [Member] | Commercial
Financing Receivable, Impaired [Line Items]
Current balance	169	1,069
Contractual Principal Balance	169	1,071
Allowance for loan and lease losses	169	550
Average Recorded Investment	1,204	1,098	1,409
Impaired Financing Receivables With Related Allowance [Member] | Lease financing
Financing Receivable, Impaired [Line Items]
Current balance	0	0
Contractual Principal Balance	0	0
Allowance for loan and lease losses	0	0
Average Recorded Investment	0	214	0
Impaired Financing Receivables With Related Allowance [Member] | Construction real estate
Financing Receivable, Impaired [Line Items]
Current balance	0	0
Contractual Principal Balance	0	0
Allowance for loan and lease losses	0	0
Average Recorded Investment	0	0	0
Impaired Financing Receivables With Related Allowance [Member] | Commercial real estate
Financing Receivable, Impaired [Line Items]
Current balance	3,119	8,228
Contractual Principal Balance	3,120	8,277
Allowance for loan and lease losses	448	593
Average Recorded Investment	2,634	7,792	12,928
Impaired Financing Receivables With Related Allowance [Member] | Residential real estate
Financing Receivable, Impaired [Line Items]
Current balance	1,056	1,189
Contractual Principal Balance	1,063	1,189
Allowance for loan and lease losses	160	179
Average Recorded Investment	1,112	1,374	1,696
Impaired Financing Receivables With Related Allowance [Member] | Home equity
Financing Receivable, Impaired [Line Items]
Current balance	100	101
Contractual Principal Balance	100	101
Allowance for loan and lease losses	2	2
Average Recorded Investment	101	101	101
Impaired Financing Receivables With Related Allowance [Member] | Installment
Financing Receivable, Impaired [Line Items]
Current balance	0	0
Contractual Principal Balance	0	0
Allowance for loan and lease losses	0	0
Average Recorded Investment	$ 0	$ 0	$ 0

LOANS - Changes in Other Real E

LOANS - Changes in Other Real Estate Owned (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of year	$ 6,284	$ 13,254	$ 22,674
Additions	4,119	2,872	8,398
SEC Schedule III, Real Estate, Cost of Real Estate Sold	6,983	9,356	15,817
Valuation adjustments	(639)	(486)	(2,001)
Balance at end of year	2,781	6,284	13,254
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additions	1,732	1,850	5,187
SEC Schedule III, Real Estate, Cost of Real Estate Sold	5,409	6,993	12,722
Valuation adjustments	(439)	(345)	(1,617)
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additions	2,387	1,022	3,211
SEC Schedule III, Real Estate, Cost of Real Estate Sold	1,574	2,363	3,095
Valuation adjustments	$ (200)	$ (141)	$ (384)

ALLOWANCE FOR LOAN AND LEASE 65

ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in the Allowance for Loan and Lease Losses for the Previous Three Years (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Balance at beginning of year	$ 49,422	$ 43,149	$ 42,820
Provision for loan and lease losses	8,038	9,322	7,926
Loans charged off	(12,712)	(6,652)	(11,660)
Recoveries	4,124	3,603	4,063
Balance at end of year	48,872	49,422	43,149
Balance at beginning of year, covered	8,539	10,249	10,038
Provision for loan and lease losses - covered	(4,456)	818	1,715
Loans charged-off	951	4,462	8,896
Recoveries	2,017	1,934	7,392
Balance at end of year, covered	5,149	8,539	10,249
Balance at beginning of year	57,961	53,398	52,858
Provision for loan and lease losses	3,582	10,140	9,641
Loans charged-off	13,663	11,114	20,556
Recoveries	6,141	5,537	11,455
Balance at end of year	$ 54,021	$ 57,961	$ 53,398

ALLOWANCE FOR LOAN AND LEASE 66

ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in the Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan and lease losses:
Balance at beginning of year	$ 57,961	$ 53,398	$ 52,858
Provision for loan and lease losses	3,582	10,140	9,641
Loans charged-off	13,663	11,114	20,556
Recoveries	6,141	5,537	11,455
Total net charge-offs	(7,522)	(5,577)	(9,101)
Balance at end of year	54,021	57,961	53,398
Ending allowance on loans individually evaluated for impairment	779	1,324
Ending allowance on loans collectively evaluated for impairment	53,242	56,637
Loans and Leases:
Ending balance of loans individually evaluated for impairment	41,627	47,970
Ending balance of loans collectively evaluated for impairment	5,971,556	5,709,512
Loans and Leases Receivable, Net of Deferred Income	6,013,183	5,757,482
Commercial
Allowance for loan and lease losses:
Balance at beginning of year	19,225	16,995	13,870
Provision for loan and lease losses	6,917	3,705	4,809
Loans charged-off	10,194	2,630	5,408
Recoveries	1,650	1,155	3,724
Total net charge-offs	(8,544)	(1,475)	(1,684)
Balance at end of year	17,598	19,225	16,995
Ending allowance on loans individually evaluated for impairment	169	550
Ending allowance on loans collectively evaluated for impairment	17,429	18,675
Impaired Financing Receivable, Related Allowance	17,598	19,225
Loans and Leases:
Ending balance of loans individually evaluated for impairment	7,331	13,203
Ending balance of loans collectively evaluated for impairment	1,905,412	1,768,745
Loans and Leases Receivable, Net of Deferred Income	1,912,743	1,781,948
Lease financing
Allowance for loan and lease losses:
Balance at beginning of year	716	821	435
Provision for loan and lease losses	(42)	(106)	384
Loans charged-off	0	0	0
Recoveries	1	1	2
Total net charge-offs	1	1	2
Balance at end of year	675	716	821
Ending allowance on loans individually evaluated for impairment	0	0
Ending allowance on loans collectively evaluated for impairment	675	716
Loans and Leases:
Ending balance of loans individually evaluated for impairment	82	195
Ending balance of loans collectively evaluated for impairment	89,265	92,913
Loans and Leases Receivable, Net of Deferred Income	89,347	93,108
Construction real estate
Allowance for loan and lease losses:
Balance at beginning of year	3,282	1,810	1,045
Provision for loan and lease losses	207	1,280	597
Loans charged-off	1	93	85
Recoveries	89	285	253
Total net charge-offs	88	192	168
Balance at end of year	3,577	3,282	1,810
Ending allowance on loans individually evaluated for impairment	0	0
Ending allowance on loans collectively evaluated for impairment	3,577	3,282
Impaired Financing Receivable, Related Allowance	3,577	3,282
Loans and Leases:
Ending balance of loans individually evaluated for impairment	29	0
Ending balance of loans collectively evaluated for impairment	467,701	399,434
Loans and Leases Receivable, Net of Deferred Income	467,730	399,434
Commercial real estate
Allowance for loan and lease losses:
Balance at beginning of year	26,540	23,656	27,086
Provision for loan and lease losses	(7,291)	5,365	1,439
Loans charged-off	1,038	4,983	10,083
Recoveries	2,719	2,502	5,214
Total net charge-offs	1,681	(2,481)	(4,869)
Balance at end of year	20,930	26,540	23,656
Ending allowance on loans individually evaluated for impairment	448	593
Ending allowance on loans collectively evaluated for impairment	20,482	25,947
Impaired Financing Receivable, Related Allowance	20,930	26,540
Loans and Leases:
Ending balance of loans individually evaluated for impairment	21,542	20,460
Ending balance of loans collectively evaluated for impairment	2,468,549	2,407,117
Loans and Leases Receivable, Net of Deferred Income	2,490,091	2,427,577
Residential real estate
Allowance for loan and lease losses:
Balance at beginning of year	3,208	4,014	3,753
Provision for loan and lease losses	1,695	(655)	1,234
Loans charged-off	435	387	1,531
Recoveries	215	236	558
Total net charge-offs	(220)	(151)	(973)
Balance at end of year	4,683	3,208	4,014
Ending allowance on loans individually evaluated for impairment	160	179
Ending allowance on loans collectively evaluated for impairment	4,523	3,029
Impaired Financing Receivable, Related Allowance	4,683	3,208
Loans and Leases:
Ending balance of loans individually evaluated for impairment	7,932	9,601
Ending balance of loans collectively evaluated for impairment	463,459	491,379
Loans and Leases Receivable, Net of Deferred Income	471,391	500,980
Home equity
Allowance for loan and lease losses:
Balance at beginning of year	3,043	3,943	4,260
Provision for loan and lease losses	1,778	(175)	573
Loans charged-off	913	1,445	1,891
Recoveries	1,027	720	1,001
Total net charge-offs	114	(725)	(890)
Balance at end of year	4,935	3,043	3,943
Ending allowance on loans individually evaluated for impairment	2	2
Ending allowance on loans collectively evaluated for impairment	4,933	3,041
Impaired Financing Receivable, Related Allowance	4,935	3,043
Loans and Leases:
Ending balance of loans individually evaluated for impairment	4,456	4,074
Ending balance of loans collectively evaluated for impairment	489,148	456,314
Loans and Leases Receivable, Net of Deferred Income	493,604	460,388
Installment
Allowance for loan and lease losses:
Balance at beginning of year	388	386	407
Provision for loan and lease losses	(90)	53	25
Loans charged-off	225	386	509
Recoveries	234	335	463
Total net charge-offs	9	(51)	(46)
Balance at end of year	307	388	386
Ending allowance on loans individually evaluated for impairment	0	0
Ending allowance on loans collectively evaluated for impairment	307	388
Impaired Financing Receivable, Related Allowance	307	388
Loans and Leases:
Ending balance of loans individually evaluated for impairment	255	437
Ending balance of loans collectively evaluated for impairment	41,331	50,202
Loans and Leases Receivable, Net of Deferred Income	41,586	50,639
Credit card
Allowance for loan and lease losses:
Balance at beginning of year	1,559	1,773	2,002
Provision for loan and lease losses	408	673	580
Loans charged-off	857	1,190	1,049
Recoveries	206	303	240
Total net charge-offs	(651)	(887)	(809)
Balance at end of year	1,316	1,559	$ 1,773
Ending allowance on loans individually evaluated for impairment	0	0
Ending allowance on loans collectively evaluated for impairment	1,316	1,559
Impaired Financing Receivable, Related Allowance	1,316	1,559
Loans and Leases:
Ending balance of loans individually evaluated for impairment	0	0
Ending balance of loans collectively evaluated for impairment	46,691	43,408
Loans and Leases Receivable, Net of Deferred Income	$ 46,691	$ 43,408

PREMISES AND EQUIPMENT - Schedu

PREMISES AND EQUIPMENT - Schedule of Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 222,550	$ 227,733
Less accumulated depreciation and amortization	97,514	96,154
Total premises and equipment	125,036	131,579
Operating Leases, Rent Expense	7,100	7,900	$ 7,000
Land and land improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	41,711	41,112
Buildings [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	104,576	107,918
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	55,165	55,368
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	19,377	19,544
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 1,721	$ 3,791

PREMISES AND EQUIPMENT - Operat

PREMISES AND EQUIPMENT - Operating leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leased Assets [Line Items]
2,012	$ 6,468
2,013	6,212
2,014	5,962
2,015	5,161
2,016	3,112
Thereafter	8,346
Total	$ 35,261

GOODWILL AND OTHER INTANGIBLE69

GOODWILL AND OTHER INTANGIBLE ASSETS GOODWILL AND OTHER INTANGIBLE ASSETS-Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Balance at beginning of year	$ 204,084	$ 204,084	$ 137,739
Goodwill	0	0	66,345
Balance at end of year	$ 204,084	$ 204,084	$ 204,084

GOODWILL AND OTHER INTANGIBLE70

GOODWILL AND OTHER INTANGIBLE ASSETS GOODWILL AND OTHER INTANGIBLE ASSETS-Schedule of Future Amortization Expense (Details) $ in Thousands	Dec. 31, 2017USD ($)
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 1,097
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1,020
Finite-Lived Intangible Assets, Amortization Expense, Year Three	788
Finite-Lived Intangible Assets, Amortization Expense, Year Four	636
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 189

GOODWILL AND OTHER INTANGIBLE71

GOODWILL AND OTHER INTANGIBLE ASSETS GOODWILL AND OTHER INTANGIBLE ASSETS--Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Other intangibles	$ 5,300	$ 6,500
Finite-Lived Core Deposits, Gross	3,300	4,500
Finite-Lived Intangible Assets, Period Increase (Decrease)	0	0
Finite-Lived Intangible Assets, Amortization Expense	$ 1,300	$ 1,600	$ 1,900
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization method	accelerated basis
Estimated weighted average life (in years)	3 years 11 months

DEPOSITS DEPOSITS (Details)

DEPOSITS DEPOSITS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Time Deposit Maturities, Next Twelve Months	$ 783,451
Time Deposit Maturities, Year Two	315,274
Time Deposit Maturities, Year Three	122,165
Time Deposit Maturities, Year Four	68,532
Time Deposit Maturities, Year Five	27,394
Time Deposit Maturities, after Year Five	289
Time	$ 1,317,105	$ 1,321,843

DEPOSITS DEPOSITS-Additional In

DEPOSITS DEPOSITS-Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Time Deposits, at or Above FDIC Insurance Limit	$ 174.8	$ 190.9

BORROWINGS - Schedule of Short-

BORROWINGS - Schedule of Short-term Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000
Commitments outstanding to extend credit	0	$ 0
Short-term Debt	$ 814,565	$ 807,912	$ 938,425
Total long-term debt	1.32%	0.58%	0.44%
Short-term debt, rate (as a percent)	0.98%	0.50%	0.22%
Short-term debt, average for the year	$ 830,365	$ 880,457	$ 625,674
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 72,265	$ 120,212	$ 89,325
Total long-term debt	0.19%	0.12%	0.11%
Short-term debt, rate (as a percent)	0.19%	0.05%	0.07%
Short-term debt, average for the year	$ 69,766	$ 89,157	$ 73,191
Short-term debt, maximum month-end balances	130,633	122,242	123,374
Federal Home Loan Bank Borrowings [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 742,300	$ 687,700	$ 849,100
Total long-term debt	1.43%	0.66%	0.47%
Short-term debt, rate (as a percent)	1.05%	0.55%	0.24%
Short-term debt, average for the year	$ 760,558	$ 791,259	$ 552,360
Short-term debt, maximum month-end balances	$ 957,700	$ 1,035,000	$ 849,100
Short-term Debt [Member]
Short-term Debt [Line Items]
Short-term debt, rate (as a percent)	4.07%	3.56%	3.30%
Short-term debt, average for the year	$ 41	$ 41	$ 123
Short-term debt, maximum month-end balances	$ 0	$ 0	$ 15,000

BORROWINGS - Schedule of Long-t

BORROWINGS - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amount
Subordinated Debt	$ 120,000	$ 120,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(1,362)	(1,537)
FHLB long-term advances	241	351
Other Long-term Debt	775	775
Total long-term debt	$ 119,654	$ 119,589
Average Rate [Abstract]
Debt, Weighted Average Interest Rate	5.13%	5.13%
Federal Home Loan Bank	1.09%	1.43%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	0.00%	0.00%
Long-term Debt, Weighted Average Interest Rate, at Point in Time	5.14%	5.15%
Maturities of Long-term Debt [Abstract]
2,013	$ 15
2,014	226
2,015	0
2,016	0
2,017	0
Thereafter	$ 119,413

BORROWINGS Borrowings - - Addit

BORROWINGS Borrowings - - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Commitments outstanding to extend credit	$ 0	$ 0
Subordinated debt, original issue	$ 120,000
Subordinated Borrowing, Interest Rate	5.125%
Book value of FHLB collateral	$ 3,600,000

DERIVATIVES - Additional Inform

DERIVATIVES - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)entity	Dec. 31, 2016USD ($)entity
Derivative [Line Items]
Maximum derivative notional position as a percentage of assets	35.00%
Maximum credit exposure as a percentage of capital	3.00%
Maximum single counterparty credit risk exposure	$ 20,000
Number of counterparties | entity	13	10
Interest-bearing deposit swap	$ 1,674,080	$ 1,354,056
Derivative Liability	12,687	12,587
Other Credit Derivatives [Member]
Derivative [Line Items]
Outstanding liability from counterparty contracts	100	200
Interest-bearing deposit swap	15,400	17,800
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Interest-bearing deposit swap	12,300	13,200
Credit Risk Contract [Member]
Derivative [Line Items]
Interest-bearing deposit swap	95,900	64,900
Derivative [Member] | Other Liabilities [Member]
Derivative [Line Items]
Interest-bearing deposit swap	837,500	677,800
Derivative Liability	$ 1,300	$ 5,200

DERIVATIVES - Summary of Deriva

DERIVATIVES - Summary of Derivative Financial Instruments and Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Interest-bearing deposit swap	$ 1,674,080	$ 1,354,056
Estimate Fair Value Gain	12,682	12,559
Estimate Fair Value Loss	(12,687)	(12,587)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Interest-bearing deposit swap	837,040	677,028
Estimate Fair Value Gain	5,529	4,158
Estimate Fair Value Loss	(7,158)	(8,429)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other assets
Derivatives, Fair Value [Line Items]
Interest-bearing deposit swap	837,040	677,028
Estimate Fair Value Gain	7,153	8,401
Estimate Fair Value Loss	$ (5,529)	$ (4,158)

DERIVATIVES DERIVATIVES - Discl

DERIVATIVES DERIVATIVES - Disclosure by Type of Financial Instrument (Details) - Fair Value Hedges - Matched interest rate swaps - Accrued interest and other liabilities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 12,687	$ 12,587
Derivative Liability, Fair Value, Gross Asset	2,279	(462)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 14,966	$ 12,125

DERIVATIVES - Derivative Financ

DERIVATIVES - Derivative Financial Instruments, Average Remaining Maturity and the Weighted-Average Interest Rates being Paid and Received (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional Value	$ 1,674,080	$ 1,354,056
Asset conversion swaps
Derivative [Line Items]
Notional Value	$ 1,674,080
Average Maturity (years)	5 years 11 months
Fair Value	$ (5)
Weighted-Average Rate Receive	4.01%
Weighted-Average Rate Pay	4.01%
Asset conversion swaps | Derivative Financial Instruments Receive Fixed Pay Variable
Derivative [Line Items]
Notional Value	$ 837,040
Average Maturity (years)	5 years 11 months
Fair Value	$ 1,624
Weighted-Average Rate Receive	4.37%
Weighted-Average Rate Pay	3.66%
Asset conversion swaps | Derivative Financial Instruments Receive Variable Pay Fixed
Derivative [Line Items]
Notional Value	$ 837,040
Average Maturity (years)	5 years 11 months
Fair Value	$ (1,629)
Weighted-Average Rate Receive	3.66%
Weighted-Average Rate Pay	4.37%

RELATED PARTIES TRANSACTIONS (D

RELATED PARTIES TRANSACTIONS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Loans to Related Parties [Roll Forward]
Beginning balance	$ 6,930
Additions	3,904
Deductions	(961)
Ending balance	9,873
Loans 90 days past due	$ 0

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Line Items]
Letters of credit issued to guarantee performance of a client to a third party	$ 25,300,000	$ 18,400,000
Affordable Housing Program Obligation	35,900,000	32,700,000
Commitments outstanding to extend credit	0	0
Loans and Leases Receivable, Commitments, Variable Rates	2,000,000,000
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	16,806,000	2,691,000	$ 1,388,000
Income tax expense	19,376,000	42,205,000	35,870,000
Other Noninterest Expense	40,236,000	23,370,000	$ 27,377,000
Amortization Method Qualified Affordable Housing Project Investments, Amortization	4,200,000	2,700,000
Affordable housing contingent commitment	0	0
Estimated Litigation Liability	0	0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	3,000,000	4,900,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	3,000,000	13,700,000
Loans and Leases Receivable, Commitments, Fixed Rates	$ 44,300,000
Loan Commitments, Fixed Interest Rate Range, Minimum	0.00%
Loan Commitments, Fixed Interest Rate Range, Maximum	21.00%
Loan Commitments, Fixed Rate, Maturities, Minimum	1 year
Loan Commitments, Fixed Rate, Maturities, Maximum	29 years
Commitments to Extend Credit
Commitments and Contingencies Disclosure [Line Items]
Commitments outstanding to extend credit	$ 2,100,000,000	2,000,000,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Loans and Leases Receivable, Commitments, Variable Rates		0
Maximum
Commitments and Contingencies Disclosure [Line Items]
Loans and Leases Receivable, Commitments, Variable Rates		0.2100
Affordable housing investment [Member]
Commitments and Contingencies Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	3,200,000	2,100,000
Historic tax credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	13,700,000	$ 600,000
Income tax expense	12,500,000
Other Noninterest Expense	$ 11,300,000

INCOME TAXES (Detail)

INCOME TAXES (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current expense [Abstract]
Federal	$ 22,599	$ 40,537	$ 31,428
State	1,265	1,322	250
Total current expense	23,864	41,859	31,678
Deferred (benefit) expense [Abstract]
Federal	(4,657)	528	3,980
State	169	(182)	212
Total deferred (benefit) expense	(4,488)	346	4,192
Income tax expense	19,376	42,205	35,870
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes computed at federal statutory rate (35%) on income before income taxes	40,657	45,756	38,827
Benefit from tax-exempt income	(3,427)	(2,911)	(2,815)
Tax credits	(16,806)	(2,691)	(1,388)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	(8,191)	0	0
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount	4,599	0	0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	(1,449)	(72)	(35)
State income taxes, net of federal tax benefit	932	741	301
Effective Income Tax Rate Reconciliation, ASU 2014-10, Affordable Housing Amortization, Amount	2,798	1,923	455
Other	263	(541)	525
Income tax expense	19,376	42,205	35,870
Deferred tax assets [Abstract]
Allowance for loan and lease losses	12,134	20,955
Deferred compensation	384	627
Postretirement benefits other than pension liability	564	925
Accrued stock-based compensation	932	1,094
Other real estate owned write-downs	97	888
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Impairment Losses	616	844
Accrued expenses	3,051	5,081
Deferred Tax Assets, Unrealized Losses on Investment Securities and Derivatives	249	3,141
Other	708	453
Total deferred tax assets	18,735	34,008
Deferred tax liabilities [Abstract]
Tax depreciation greater than book depreciation	(2,510)	(5,166)
FHLB and FRB stock	(3,384)	(5,535)
Mortgage-servicing rights	(343)	(530)
Leasing activities	(2,792)	(4,933)
Deferred Tax Liabilities, Prepaid Pension Cost	8,888	12,539
Intangible assets	(11,559)	(16,611)
Deferred loan fees and costs	(371)	(1,238)
Prepaid expenses	(210)	(348)
Deferred Tax Liabilities, Partnership Interests	1,230	1,218
Fair value adjustments on acquisitions	0	(1,404)
Other	(2,415)	(852)
Deferred Tax Liabilities, Gross	(33,702)	(50,374)
Total deferred tax liabilities	(14,967)	(16,366)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized tax benefits affecting income tax rate	2,900	2,400
Balance at beginning of year	3,735	0
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	0	3,735
Balance at end of year	$ 3,735	$ 3,735	$ 0
Future Effective Income Tax Rate At Federal Statutory Income Tax Rate	21.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 4,901	$ 5,373
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 4,901	5,373
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year				$ 0
Defined Contribution Plan, Maximum Annual Contribution Percent by Employee	50.00%
Payment for Pension Benefits	$ 0	0	$ 0
Pension Cost (Reversal of Cost)	628	1,153	1,042
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	62,729	60,664
Service cost	4,894	5,034	4,807
Interest cost	2,325	2,262	2,120
Actuarial gain (loss)	6,107	142
Benefit obligation at end of year	71,154	62,729	60,664
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	131,011	125,714
Actual return on plan assets	18,239	10,670
Fair value of plan assets at end of year	144,349	131,011	125,714
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Assets				73,195	$ 68,282
Liabilities				0	0
Net amount recognized				73,195	68,282
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), after Tax [Abstract]
Net actuarial loss				33,580	38,278
Net prior service cost				(1,921)	(2,334)
Deferred tax assets				(12,028)	(13,141)
Net amount recognized				19,631	22,803	$ 24,048	$ 17,904
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(3,172)	(1,245)	6,144
Accumulated benefit obligation				69,678	61,909
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	4,894	5,034	4,807
Interest cost	2,325	2,262	2,120
Expected return on plan assets	(9,358)	(9,644)	(9,444)
Amortization of prior service cost	(413)	(413)	(413)
Defined Benefit Plan, Amortization of Gain (Loss)	1,924	1,608	1,888
Net periodic benefit (income) cost	(628)	(1,153)	(1,042)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Gain (Loss), before Tax	(2,775)	(884)	11,014
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	0	0	0
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost, before Tax	413	413	413
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(1,924)	(1,608)	(1,888)
Total recognized in accumulated other comprehensive income	(4,286)	(2,079)	9,539
Total recognized in net periodic benefit cost and accumulated other comprehensive income	$ (4,914)	$ (3,232)	$ 8,497
Amortization of loss				2,090	1,754	1,642
Amortization of prior service credit				$ (413)	$ (413)	$ (413)
Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate				3.43%	3.88%	4.05%
Rate of compensation increase				3.50%	3.50%	3.50%
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.88%	4.05%	3.76%
Expected return on plan assets	7.25%	7.50%	7.50%
Rate of compensation increase	3.50%	3.50%	3.50%
Fair value measurments	$ 131,011	$ 125,714	$ 125,714	$ 144,349	$ 131,011	$ 125,714
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
2,017				4,758
2,018				4,426
2,019				5,417
2,020				5,771
2,021				5,016
Thereafter				29,825
Defined Contribution Plan [Abstract]
Defined Contribution Plan, Cost	1,900	800	$ 0
Cash Surrender Value of Life Insurance				102,300	98,500
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends				144,349	131,010
Fair Value, Inputs, Level 1 [Member]
Defined Contribution Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends				137,496	124,984
Fair Value, Inputs, Level 2 [Member]
Defined Contribution Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends				6,853	6,026
Fair Value, Inputs, Level 3 [Member]
Defined Contribution Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends				0	0
Cash
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	190
Fair value of plan assets at end of year	175	190
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	190	190		175	190
Cash | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	190
Fair value of plan assets at end of year	175	190
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	190	190		175	190
Cash | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
Cash | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
US Government Agencies Debt Securities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	6,026
Fair value of plan assets at end of year	6,853	6,026
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	6,026	6,026		6,853	6,026
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	6,026
Fair value of plan assets at end of year	6,853	6,026
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	6,026	6,026		6,853	6,026
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
Fixed income mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	66,483
Fair value of plan assets at end of year	69,154	66,483
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	66,483	66,483		69,154	66,483
Fixed income mutual funds | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	66,483
Fair value of plan assets at end of year	69,154	66,483
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	66,483	66,483		69,154	66,483
Fixed income mutual funds | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
Fixed income mutual funds | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
Equity mutual funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	58,311
Fair value of plan assets at end of year	68,167	58,311
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	58,311	58,311		68,167	58,311
Equity mutual funds | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	58,311
Fair value of plan assets at end of year	68,167	58,311
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	58,311	58,311		68,167	58,311
Equity mutual funds | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	0	0		0	0
Equity mutual funds | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Fair value measurments	$ 0	$ 0		$ 0	$ 0

EMPLOYEE BENEFIT PLANS Defined

EMPLOYEE BENEFIT PLANS Defined Benefit Plan, Fair Value on Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
defined benefit plan, fair value of plan assets excluding accrued interest and dividends [Line Items]
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 4,901	$ 5,373
Defined Contribution Plan, Cost	1,900	800	$ 0
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends	144,349	131,010
Fair Value, Inputs, Level 1 [Member]
defined benefit plan, fair value of plan assets excluding accrued interest and dividends [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends	137,496	124,984
Fair Value, Inputs, Level 2 [Member]
defined benefit plan, fair value of plan assets excluding accrued interest and dividends [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends	6,853	6,026
Fair Value, Inputs, Level 3 [Member]
defined benefit plan, fair value of plan assets excluding accrued interest and dividends [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets Excluding Accrued Interest and Dividends	$ 0	$ 0

ACCUMULATED OTHER COMPREHENSI86

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Comprehensive Income (Loss), before Reclassification Adjustments and Tax [Abstract]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	$ 8,447	$ 751	$ (2,200)
Unrealized gain (loss) on derivatives	810	809	(1,020)
Retirement obligations	2,775	884	(11,014)
Foreign currency translation			50
Total	12,032	2,444	(14,184)
Other Comprehensive Income (Loss) Reclassifications before Tax [Abstract]
Unrealized gain (loss) on investment securities	1,649	234	1,505
Unrealized gain (loss) on derivatives	0	0	0
Retirement obligation	1,511	1,195	1,475
Foreign currency translation			0
Total	138	(961)	30
Transactions Pre-tax
Unrealized gain (loss) on investment securities	6,798	517	(3,705)
Unrealized gain (loss) on derivatives	810	809	(1,020)
Retirement obligation	4,286	2,079	(9,539)
Foreign currency translation			50
Total	11,894	3,405	(14,214)
Transactions Tax-effect
Unrealized gain (loss) on investment securities	(2,431)	(133)	1,278
Unrealized gain (loss) on derivatives	(296)	(301)	370
Retirement obligation	(1,114)	(834)	3,395
Foreign currency translation			0
Total	(3,841)	(1,268)	5,043
Transactions Net of tax
Unrealized gain (loss) on investment securities	4,367	384	(2,427)
Unrealized gain (loss) on derivatives	514	508	(650)
Retirement obligation	3,172	1,245	(6,144)
Foreign currency translation	0	0	50
Total	8,053	2,137	(9,171)
Balances Net of tax
Unrealized gain (loss) on investment securities	(182)	(4,549)	(4,933)	$ (2,506)
Unrealized gain (loss) on derivatives	(577)	(1,091)	(1,599)	(949)
Retirement obligation	(19,631)	(22,803)	(24,048)	(17,904)
Foreign currency translation			0	(50)
Total	$ (20,390)	$ (28,443)	$ (30,580)	$ (21,409)

ACCUMULATED OTHER COMPREHENSI87

ACCUMULATED OTHER COMPREHENSIVE INCOME AMOUNT RECLASSIFIED FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net gains (losses) on sales of investment securities	$ 1,649	$ 234	$ 1,505
Amortization of prior service cost	413	413	413
Recognized net actuarial loss	(1,924)	(1,608)	(1,888)
Other Comprehensive Income, Reclassification, Amortization of Defined Benefit Plans items, Pre-tax	(1,511)	(1,195)	(1,475)
Total reclassifications for the period, before tax	$ 138	$ (961)	$ 30

CAPITAL - Risk-Based Capital(De

CAPITAL - Risk-Based Capital(Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One Capital	$ 755,735	$ 703,891
Subordinated debt, original issue	120,000
Excess Capital	$ 271,600
Risk Based Ratios [Abstract]
Common Equity Tier One Capital to Risk-Weighted Assets	10.63%	10.46%
Common Equity Tier One Capital Required for Capital Adequacy	$ 408,746	$ 344,848
Common Equity Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	5.75%	5.125%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy Fully Phased In Basel III	$ 497,604	$ 471,012
Common Equity Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Fully Phased In Basel III	7.00%	7.00%
Tier One Risk Based Capital	$ 755,839	$ 703,995
Tier One Risk Based Capital to Risk Weighted Assets	10.63%	10.46%
Tier One Risk Based Capital Required for Capital Adequacy	$ 515,376	$ 445,779
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	7.25%	6.625%	4.00%
Capital Conservation Buffer-Fully Phased-In	2.50%
Capital Conservation Buffer-Phased-In Incremental Change	0.625%
Tier One Risk Based Capital [Abstract]
Tier One Risk Based Capital Required for Capital Adequacy Fully Phased In Basel III	$ 604,233	$ 571,943
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Fully Phased In Basel III	8.50%	8.50%
Capital	$ 929,148	$ 881,158
Capital to Risk Weighted Assets	13.07%	13.10%
Capital Required for Capital Adequacy	$ 657,548	$ 580,354
Capital Required for Capital Adequacy to Risk Weighted Assets	9.25%	8.625%
Capital [Abstract]
Capital Required for Capital Adequacy Fully Phased In Basel III	$ 746,406	$ 706,517
Capital Required for Capital Adequacy to Risk Weighted Assets Fully Phased In Basel III	10.50%	10.50%
Tier One Leverage Capital	$ 755,839	$ 703,995
Tier One Leverage Capital [Abstract]
Tier One Leverage Capital Required for Capital Adequacy Fully Phased In Basel III	$ 342,198	$ 327,562
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Fully Phased In Basel III	4.00%	4.00%
Tier One Leverage Capital to Average Assets	8.84%	8.60%
Tier One Leverage Capital Required for Capital Adequacy	$ 342,198	$ 327,562
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Subsidiaries [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One Capital	$ 794,251	$ 747,151
Risk Based Ratios [Abstract]
Common Equity Tier One Capital to Risk-Weighted Assets	11.21%	11.13%
Common Equity Tier One Capital Required for Capital Adequacy	$ 407,220	$ 344,038
Common Equity Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets	5.75%	5.125%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy Fully Phased In Basel III	$ 495,746	$ 469,906
Common Equity Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Fully Phased In Basel III	7.00%	7.00%
Tier One Risk Based Capital	$ 794,355	$ 747,255
Tier One Risk Based Capital to Risk Weighted Assets	11.22%	11.13%
Tier One Risk Based Capital Required for Capital Adequacy	$ 513,452	$ 444,732
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	7.25%	6.625%
Common Equity Tier One Risk Based Capital Required to be Well Capitalized To Risk Weighted Assets	$ 460,336	$ 436,341
Common Equity Tier One Risk Based Capital Required to be Well Capitalized To Risk Weighted Assets	6.50%	6.50%
Tier One Risk Based Capital [Abstract]
Tier One Risk Based Capital Required for Capital Adequacy Fully Phased In Basel III	$ 601,978	$ 570,600
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Fully Phased In Basel III	8.50%	8.50%
Capital	$ 856,363	$ 813,433
Capital to Risk Weighted Assets	12.09%	12.12%
Capital Required for Capital Adequacy	$ 655,093	$ 578,991
Capital Required for Capital Adequacy to Risk Weighted Assets	9.25%	8.625%
Capital [Abstract]
Capital Required for Capital Adequacy to Risk Weighted Assets	$ 566,567	$ 537,035
Capital Required for Capital Adequacy Fully Phased In Basel III	$ 743,619	$ 704,859
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Capital Required for Capital Adequacy to Risk Weighted Assets Fully Phased In Basel III	10.50%	10.50%
Tier One Leverage Capital	$ 794,355	$ 747,255
Tier One Leverage Capital [Abstract]
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	708,209	671,294
Tier One Leverage Capital Required for Capital Adequacy Fully Phased In Basel III	$ 342,113	$ 327,392
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets Fully Phased In Basel III	4.00%	4.00%
Tier One Leverage Capital to Average Assets	9.29%	9.13%
Tier One Leverage Capital Required for Capital Adequacy	$ 342,113	$ 327,392
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	$ 427,642	$ 409,240
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%

CAPITAL - Share Repurchase (Det

CAPITAL - Share Repurchase (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 23, 2012
Capital [Abstract]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				5,000,000
Treasury Stock, Shares, Acquired	0	0	239,967
Treasury Stock Acquired, Average Cost Per Share			$ 18.75
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	3,509,133

STOCK OPTIONS AND AWARDS (Detai

STOCK OPTIONS AND AWARDS (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation | $	$ 5,446	$ 5,354	$ 4,049
Total unrecognized compensation cost | $				$ 5,500
Unrecognized compensation cost, period for recognition (in years)	1 year 330 days
Number of plans				3
Share-based Compensation Arrangement by Share-based Payment Award, Option Term	10 years
Options outstanding at end of year	113,307	113,307		11,800
Number of Shares Available for Grant				2,154,251
Activity for stock option plan [Roll Forward]
Outstanding at beginning of year (in shares)	113,307
Granted (in shares)	0	0	0
Exercised (in shares)	(101,507)
Forfeited or expired (in shares)	0
Outstanding at end of year (in shares)	11,800	113,307
Exercised (in shares)				11,800
Weighted average exercise price, outstanding at beginning of year (in dollars per share) | $ / shares	$ 12.08
Weighted average exercise price, granted (in dollars per share) | $ / shares	0
Weighted average exercise price, exercised (in dollars per share) | $ / shares	12.13
Weighted average exercise price, forfeited or expired (in dollars per share) | $ / shares	0
Weighted average exercise price, outstanding at end of year (in dollars per share) | $ / shares	$ 11.64	$ 12.08
Weighted average exercise price, Exercisable (in dollars per share) | $ / shares				$ 11.64
Weighted average remaining contractual term, outstanding at end of year (in years)	44 days
Weighted average remaining contractual life, exercisable at end of year (in years)	44 days
Aggregate intrinsic value, outstanding at end of year | $				$ 174
Aggregate intrinsic value, exercisable at end of year | $				$ 174
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Total intrinsic value of options exercised | $	$ 1,533	$ 661	$ 492
Proceeds from exercise of stock options | $	341	801	744
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options | $	1,991	1,958	1,488
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested in period, total fair value | $	$ 5,600	$ 4,400	$ 3,800
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Number of shares nonvested at beginning of year	648,817	643,641	494,452
Number of shares granted	234,529	317,695	439,674
Number of shares vested	(307,825)	(263,713)	(227,905)
Number of shares forfeited	(107,149)	(48,806)	(62,580)
Number of shares nonvested at end of year	468,372	648,817	643,641
Weighted average of shares fair value, nonvested at beginning of year | $ / shares	$ 17.82	$ 17.21	$ 16.43
Weighted average of shares fair value granted | $ / shares	27.36	18.13	17.65
Weighted average of shares fair value vested | $ / shares	18.12	16.82	16.45
Weighted average of shares fair value forfeited | $ / shares	21.18	17.37	16.58
Weighted average of shares fair value, nonvested at end of year | $ / shares	$ 21.63	$ 17.82	$ 17.21
1999 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized				7,507,500
Award vesting rights (as a percent)	25.00%
2012 Stock Plan [Member] [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized				0

EARNINGS PER COMMON SHARE - Com

EARNINGS PER COMMON SHARE - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator for basic and diluted earnings per share -income available to common shareholders:
Net income	$ 96,787	$ 88,526	$ 75,063
Denominator for basic earnings per share - weighted average shares	61,529,460	61,206,093	61,062,657
Effect of dilutive securities -
Employee stock awards	581,329	729,335	670,282
Warrants	60,801	49,994	114,608
Denominator for diluted earnings per share - adjusted weighted average shares	62,171,590	61,985,422	61,847,547
Basic	$ 1.57	$ 1.45	$ 1.23
Diluted	$ 1.56	$ 1.43	$ 1.21

EARNINGS PER COMMON SHARE - Add

EARNINGS PER COMMON SHARE - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share Disclosure [Line Items]
Investment Warrants, Exercise Price	$ 12.12
Preferred Stock, Shares Outstanding	0	0	0
Antidilutive Stock Options
Earnings Per Share Disclosure [Line Items]
Stock options and warrants with an exercise price greater than the average market price of the common shares not included in the computation of net income per diluted share	0	0	0
Antidilutive Warrants
Earnings Per Share Disclosure [Line Items]
Stock options and warrants with an exercise price greater than the average market price of the common shares not included in the computation of net income per diluted share	104,200	114,678	322,312

FAIR VALUE DISCLOSURES - Estima

FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Detail) - USD ($)	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Financial assets
Investment securities held-to-maturity	$ 654,008,000		$ 763,254,000
Other investments	53,140,000		51,077,000
FDIC indemnification asset	1,900,000		12,000,000
Deposits
Noninterest-bearing	1,662,058,000		1,547,985,000
Savings	2,462,420,000		2,142,189,000
Time	1,317,105,000		1,321,843,000
Total deposits	6,895,046,000	$ 9,987,298	6,525,788,000
Carrying value
Financial assets
Cash and short-term investments	184,624,000		204,048,000
Investment securities held-to-maturity	654,008,000		763,254,000
Other investments	53,140,000		51,077,000
Loans held for sale	11,502,000		13,135,000
Loans and leases, net of ALLL	5,959,162,000		5,699,521,000
Interest Receivable	24,496,000		18,503,000
Deposits
Noninterest-bearing	1,662,058,000		1,547,985,000
Interest-bearing demand	1,453,463,000		1,513,771,000
Savings	2,462,420,000		2,142,189,000
Time	1,317,105,000		1,321,843,000
Total deposits	6,895,046,000		6,525,788,000
Short-term borrowings	814,565,000		807,912,000
Long-term debt	119,654,000		119,589,000
Interest Payable	5,104,000		5,049,000
Fair value
Financial assets
Cash and short-term investments	184,624,000		204,048,000
Investment securities held-to-maturity	653,101,000		763,575,000
Loans held for sale	11,502,000		13,135,000
Loans and leases, net of ALLL	6,006,656,000		5,754,845,000
Interest Receivable	24,496,000		18,503,000
Deposits
Noninterest-bearing	1,662,058,000		1,547,985,000
Interest-bearing demand	1,453,463,000		1,513,771,000
Savings	2,462,420,000		2,142,189,000
Time	1,306,674,000		1,316,333,000
Total deposits	6,884,615,000		6,520,278,000
Short-term borrowings	814,565,000		807,912,000
Long-term debt	117,908,000		117,878,000
Interest Payable	5,104,000		5,049,000
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	184,624,000		204,048,000
Investment securities held-to-maturity	0		0
Loans held for sale	0		0
Loans and leases, net of ALLL	0		0
Interest Receivable	0		0
Deposits
Noninterest-bearing	0		0
Interest-bearing demand	0		0
Savings	0		0
Time	0		0
Total deposits	0		0
Short-term borrowings	814,565,000		807,912,000
Long-term debt	0		0
Interest Payable	204,000		410,000
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0		0
Investment securities held-to-maturity	653,101,000		763,575,000
Loans held for sale	11,502,000		13,135,000
Loans and leases, net of ALLL	0		0
Interest Receivable	8,265,000		5,705,000
Deposits
Noninterest-bearing	1,662,058,000		1,547,985,000
Interest-bearing demand	1,453,463,000		1,513,771,000
Savings	2,462,420,000		2,142,189,000
Time	1,306,674,000		1,316,333,000
Total deposits	6,884,615,000		6,520,278,000
Short-term borrowings	0		0
Long-term debt	117,908,000		117,878,000
Interest Payable	4,900,000		4,639,000
Fair Value, Inputs, Level 3 [Member] | Fair value
Financial assets
Cash and short-term investments	0		0
Investment securities held-to-maturity	0		0
Loans held for sale	0		0
Loans and leases, net of ALLL	6,006,656,000		5,754,845,000
Interest Receivable	16,231,000		12,798,000
Deposits
Noninterest-bearing	0		0
Interest-bearing demand	0		0
Savings	0		0
Time	0		0
Total deposits	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Interest Payable	$ 0		$ 0

FAIR VALUE DISCLOSURES - Summar

FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measure at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Derivatives	$ 12,682	$ 12,559
Investment securities, available for sale	1,349,408	1,039,870
Liabilities
Derivatives	12,687	12,587
Fair Value, Measurements, Recurring
Assets
Derivatives	12,757	12,922
Investment securities, available for sale	1,349,408	1,039,870
Total	1,362,165	1,052,792
Liabilities
Derivatives	12,755	12,725
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 [Member]
Assets
Derivatives	0	0
Investment securities, available for sale	2,969	8,711
Total	2,969	8,711
Liabilities
Derivatives	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 [Member]
Assets
Derivatives	12,757	12,922
Investment securities, available for sale	1,346,439	1,031,159
Total	1,359,196	1,044,081
Liabilities
Derivatives	12,755	12,725
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 [Member]
Assets
Derivatives	0	0
Investment securities, available for sale	0	0
Total	0	0
Liabilities
Derivatives	$ 0	$ 0

FAIR VALUE DISCLOSURES - Summ95

FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Inputs, Level 1 [Member]
Assets
Impaired loans	$ 0	$ 0
Other Real Estate Owned, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Assets
Impaired loans	0	0
Other Real Estate Owned, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
Assets
Impaired loans	2,671	8,154
Other Real Estate Owned, Fair Value Disclosure	$ 1,086	$ 3,921

PENDING BUSINESS COMBINATION Pe

PENDING BUSINESS COMBINATION Pending Business Combination - Pro Forma Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Pro Forma Revenue	$ 204,518	$ 387,725
Business Acquisition, Pro Forma, Provision for Loan and Lease Losses	834	10,140
Business Acquisitions, Pro Forma Income Before Tax	92,591	170,132
Net Income	65,884	119,661
Business Acquisition, Pro Forma Balance Sheet Information [Abstract]
Loans and Leases Receivable, Net Amount	8,818,392	5,699,521,000	$ 5,959,162,000
Total assets	13,806,092	8,437,967,000	8,896,923,000
Deposits	9,987,298	6,525,788,000	6,895,046,000
Total shareholders' equity	$ 1,913,682	$ 865,224,000	$ 930,664,000	$ 809,376,000	$ 784,077,000

Pending Business Combination -

Pending Business Combination - Additional Information - Narrative (Details) - USD ($) $ in Billions	Jul. 27, 2017	Jul. 25, 2017
Business Acquisition [Line Items]
Business Acquisition, Number Of Shares Received by Acquiree	1.3875
Business Combination, Consideration Transferred	$ 1
Business Acqusitions, Percentage of Voting Interests Retained		65.00%
Business Acquisition, Percentage of Voting Interests Acquired		35.00%

FIRST FINANCIAL BANCORP. (PAR98

FIRST FINANCIAL BANCORP. (PARENT COMPANY ONLY) FINANCIAL INFORMATION (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Cash	$ 121,598,000	$ 114,841,000	$ 110,122,000	$ 150,650,000		$ 121,598,000	$ 114,841,000	$ 110,122,000
Investment securities, available for sale				1,349,408,000		1,039,870,000
Other investments				53,140,000		51,077,000
Premises and equipment				125,036,000		131,579,000
Total assets				8,896,923,000	$ 13,806,092	8,437,967,000
Subordinated Debt				120,000,000		120,000,000
Other liabilities				136,994,000		119,454,000
Total liabilities				7,966,259,000		7,572,743,000
Shareholders’ equity				930,664,000	$ 1,913,682	865,224,000	809,376,000	784,077,000
Total liabilities and shareholders’ equity				8,896,923,000		8,437,967,000
Income Statement [Abstract]
Noninterest income	76,142,000	69,601,000	75,202,000
Interest Expense	49,528,000	33,279,000	23,257,000
Salaries and employee benefits	132,560,000	122,361,000	111,792,000
Miscellaneous professional services	15,023,000	6,303,000	9,622,000
Income before income taxes and equity in undistributed net earnings of subsidiaries	116,163,000	130,731,000	110,933,000
Income tax benefit	19,376,000	42,205,000	35,870,000
Net income	96,787,000	88,526,000	75,063,000
Operating activities
Net income	96,787,000	88,526,000	75,063,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	12,645,000	13,037,000	13,266,000
Stock-based compensation expense	5,446,000	5,354,000	4,049,000
Deferred income taxes	(4,488,000)	346,000	4,192,000
Decrease (increase) in other assets	(23,808,000)	(5,347,000)	(33,370,000)
Net cash provided by (used in) operating activities	121,171,000	138,361,000	91,567,000
Investing activities
Net cash (paid) acquired from business combinations	0	0	(305,591,000)
Proceeds from calls and maturities of investment securities	224,690,000	186,132,000	120,953,000
Purchases of investment securities	(723,131,000)	(396,984,000)	(547,901,000)
Net cash provided by (used in) investing activities	(427,099,000)	(309,109,000)	(918,847,000)
Financing activities
Cash dividends paid on common stock	(41,178,000)	(39,125,000)	(39,070,000)
Treasury stock purchase	0	0	(4,498,000)
Proceeds from exercise of stock options, net of shares purchased	341,000	801,000	744,000
Excess tax benefit on share-based compensation	0	264,000	146,000
Net cash provided by (used in) financing activities	334,980,000	177,505,000	831,999,000
Net increase (decrease) in cash	29,052,000	6,757,000	4,719,000
Cash and due from banks at beginning of year	121,598,000	114,841,000	110,122,000
Cash and due from banks at end of year	150,650,000	121,598,000	114,841,000
Parent Company [Member]
Statement of Financial Position [Abstract]
Cash	59,285,000	106,072,000	55,192,000	57,719,000		59,285,000	$ 106,072,000	$ 55,192,000
Investment securities, available for sale				442,000		386,000
Subordinated notes from subsidiaries				7,500,000		7,500,000
Investment in subsidiaries				970,290,000		909,798,000
Premises and equipment				1,378,000		1,395,000
Other assets				26,778,000		19,487,000
Total assets				1,064,107,000		997,851,000
Subordinated Debt				118,638,000		118,463,000
Dividends payable				10,965,000		10,386,000
Other liabilities				3,840,000		3,778,000
Total liabilities				133,443,000		132,627,000
Shareholders’ equity				930,664,000		865,224,000
Total liabilities and shareholders’ equity				1,064,107,000		997,851,000
Income Statement [Abstract]
Interest income	6,000	48,000	81,000
Noninterest income	86,000	2,596,000	253,000
Dividends from subsidiaries	54,600,000	52,700,000	17,250,000
Total income	54,692,000	55,344,000	17,584,000
Interest Expense	6,152,000	6,151,000	2,157,000
Salaries and employee benefits	5,519,000	5,445,000	4,224,000
Miscellaneous professional services	970,000	711,000	723,000
Other	4,819,000	4,841,000	5,564,000
Total expenses	17,460,000	17,148,000	12,668,000
Income before income taxes and equity in undistributed net earnings of subsidiaries	37,232,000	38,196,000	4,916,000
Income tax benefit	(7,080,000)	(5,302,000)	(4,563,000)
Equity in undistributed earnings (loss) of subsidiaries	(52,475,000)	(45,028,000)	(65,584,000)
Net income	96,787,000	88,526,000	75,063,000
Operating activities
Net income	96,787,000	88,526,000	75,063,000
Adjustments to reconcile net income to net cash provided by operating activities
Equity in undistributed earnings (loss) of subsidiaries	(52,475,000)	(45,028,000)	(65,584,000)
Depreciation and amortization	193,000	192,000	78,000
Stock-based compensation expense	5,446,000	5,354,000	4,049,000
Deferred income taxes	(360,000)	584,000	(85,000)
(Decrease) increase in dividends payable	579,000	135,000	2,000
(Decrease) increase in other liabilities	(889,000)	(389,000)	1,965,000
Decrease (increase) in other assets	(6,951,000)	(9,065,000)	1,459,000
Net cash provided by (used in) operating activities	42,330,000	40,309,000	16,947,000
Investing activities
Capital contributions to subsidiaries	0	(53,000,000)	(40,000,000)
Proceeds from calls and maturities of investment securities	0	5,978,000	87,000
Purchases of investment securities	0	(333,000)	(412,000)
Net cash provided by (used in) investing activities	0	(47,355,000)	(40,325,000)
Proceeds from Issuance of Long-term Debt	0	0	120,000,000
Financing activities
Cash dividends paid on common stock	(41,178,000)	(39,125,000)	(39,070,000)
Treasury stock purchase	0	0	(4,498,000)
Proceeds from exercise of stock options, net of shares purchased	341,000	801,000	744,000
Excess tax benefit on share-based compensation	0	264,000	146,000
Other	(3,059,000)	(1,681,000)	(3,064,000)
Net cash provided by (used in) financing activities	(43,896,000)	(39,741,000)	74,258,000
Net increase (decrease) in cash	(1,566,000)	(46,787,000)	50,880,000
Cash and due from banks at beginning of year	59,285,000	106,072,000	55,192,000
Cash and due from banks at end of year	$ 57,719,000	$ 59,285,000	$ 106,072,000
Parent Company [Member] | Commercial Banks [Member]
Statement of Financial Position [Abstract]
Investment in subsidiaries				$ 970,290,000		$ 909,798,000