First Financial Bancorp. (FFBC) 10-Q 8 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	6 Months Ended
	Jun. 30, 2018	Aug. 07, 2018
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
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		97,901,046

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
ASSETS
Cash and due from banks	$ 216,667	$ 150,650
Interest-bearing deposits with other banks	37,915	33,974
Investment securities available-for-sale, at fair value (amortized cost $2,677,257 at June 30, 2018 and $1,348,227 at December 31, 2017)	2,654,909	1,349,408
Investment securities held-to-maturity (fair value $435,785 at June 30, 2018 and $653,101 at December 31, 2017)	443,957	654,008
Other investments	95,004	53,140
Loans held for sale	15,821	11,502
Loans
Commercial	2,440,596	1,912,743
Lease financing	96,198	89,347
Real estate - construction	555,468	467,730
Real estate-commercial	3,888,993	2,490,091
Real estate-residential	918,904	471,391
Home equity	835,031	493,604
Installment	100,726	41,586
Credit card	48,665	46,691
Total loans and leases	8,884,581	6,013,183
Allowance for loan and lease losses	54,076	54,021
Net loans and leases	8,830,505	5,959,162
Premises and equipment	223,950	125,036
Goodwill and other intangibles	934,656	209,379
Accrued interest and other assets	466,783	350,664
Total assets	13,920,167	8,896,923
Deposits
Interest-bearing	2,440,088	1,453,463
Savings	3,087,683	2,462,420
Time	2,104,044	1,317,105
Total interest-bearing deposits	7,631,815	5,232,988
Noninterest-bearing	2,471,932	1,662,058
Total deposits	10,103,747	6,895,046
Federal funds purchased and securities sold under agreements to repurchase	88,070	72,265
Federal Home Loan Bank short-term borrowings	1,100,233	742,300
Total short-term borrowings	1,188,303	814,565
Long-term debt	469,423	119,654
Total borrowed funds	1,657,726	934,219
Accrued interest and other liabilities	145,757	136,994
Total liabilities	11,907,230	7,966,259
SHAREHOLDERS' EQUITY
Common stock - no par value Authorized - 160,000,000 shares Issued - 101,281,794 shares in 2018 and 68,730,731 shares in 2017	1,632,572	573,109
Retained earnings	533,319	491,847
Accumulated other comprehensive loss	(43,008)	(20,390)
Treasury stock, at cost, 6,376,897 shares in 2018 and 6,661,644 shares in 2017	(109,946)	(113,902)
Total shareholders' equity	2,012,937	930,664
Total liabilities and shareholders' equity	$ 13,920,167	$ 8,896,923

CONSOLIDATED BALANCE SHEETS CON

CONSOLIDATED BALANCE SHEETS CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Available-for-sale Securities, Amortized Cost Basis	$ 2,677,257	$ 1,348,227
Held-to-maturity Securities, Fair Value	$ 435,785	$ 653,101
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	160,000,000	160,000,000
Common Stock, Shares, Issued	104,281,794	68,730,731
Treasury Stock, Shares	6,376,897	6,661,644

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest income
Loans, including fees	$ 122,290	$ 67,748	$ 197,210	$ 134,616
Investment securities
Taxable	20,844	12,598	34,514	24,206
Tax-exempt	4,068	1,457	5,725	2,810
Total interest on investment securities	24,912	14,055	40,239	27,016
Other earning assets	177	(1,014)	284	(2,015)
Total interest income	147,379	80,789	237,733	159,617
Interest expense
Deposits	14,794	8,679	25,092	15,604
Short-term borrowings	4,132	2,051	6,795	3,483
Long-term borrowings	4,474	1,539	6,055	3,078
Total interest expense	23,400	12,269	37,942	22,165
Net interest income	123,979	68,520	199,791	137,452
Provision for loan and lease losses	3,735	467	6,038	834
Net interest income after provision for loan and lease losses	120,244	68,053	193,753	136,618
Noninterest income
Service charges on deposit accounts	9,568	4,772	14,607	9,416
Trust and wealth management fees	3,697	3,405	7,651	7,152
Bankcard income	5,343	3,501	8,737	6,636
Client derivative fees	1,463	1,489	3,220	2,592
Net gain from sales of loans	2,316	1,327	2,904	2,543
Net gain (loss) on sales of investment securities	(30)	838	(30)	1,354
Other	5,899	2,122	8,105	5,125
Total noninterest income	28,256	17,454	45,194	34,818
Noninterest expenses
Salaries and employee benefits	55,531	31,544	86,633	63,294
Net occupancy	6,631	4,302	11,128	8,817
Furniture and equipment	5,298	2,136	7,338	4,313
Data processing	14,304	3,501	17,976	6,799
Marketing	2,644	982	3,445	1,492
Communication	1,118	468	1,577	915
Professional services	5,659	1,469	7,857	3,227
State intangible tax	1,078	721	1,843	1,442
FDIC assessments	1,323	1,018	2,217	1,950
Loss (gain) - other real estate owned	(283)	162	(206)	186
Other	9,452	5,253	15,235	10,166
Total noninterest expenses	102,755	51,556	155,043	102,601
Income before income taxes	45,745	33,951	83,904	68,835
Income tax expense	9,327	11,215	16,980	21,685
Net income	$ 36,418	$ 22,736	$ 66,924	$ 47,150
Earnings per common share
Basic	$ 0.37	$ 0.37	$ 0.84	$ 0.77
Diluted	0.37	0.37	0.83	0.76
Cash dividends declared per share	$ 0.19	$ 0.17	$ 0.38	$ 0.34
Average common shares outstanding - basic	97,347,533	61,543,478	79,599,709	61,471,347
Average common shares outstanding - diluted	98,432,072	62,234,022	80,629,495	62,187,473

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 36,418	$ 22,736	$ 66,924	$ 47,150
Other comprehensive (loss) income, net of tax
Unrealized gain (loss) on investment securities arising during the period	(8,978)	4,076	(18,808)	5,563
Change in retirement obligation	494	213	817	402
Unrealized gain (loss) on derivatives	159	128	315	256
Other comprehensive income (loss)	(8,325)	4,417	(17,676)	6,221
Comprehensive income	$ 28,093	$ 27,153	$ 49,248	$ 53,371

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
Beginning Balances (in shares) at Dec. 31, 2016		68,730,731			(6,751,179)
Beginning Balances at Dec. 31, 2016	$ 865,224	$ 570,382	$ 437,188	$ (28,443)	$ (113,903)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,150		47,150
Other comprehensive income (loss)	6,221			6,221
Cash dividends declared :
Common stock at $0.38 per share in 2018 and $0.34 per share in 2017	(21,088)		(21,088)
Stock Issued During Period, Shares, Other					1,484
Adjustments to Additional Paid in Capital, Other	0	(25)			$ 25
Exercise of stock options, net of shares purchased (in shares)					39,062
Exercise of stock options, net of shares purchased	198	(462)			$ 660
Restricted stock awards, net of forfeitures (in shares)					120,973
Restricted stock awards, net of forfeitures	(2,554)	(3,559)			$ 1,005
Share-based compensation expense	2,966	$ 2,966
Ending Balances (in shares) at Jun. 30, 2017		68,730,731			(6,589,660)
Ending Balances at Jun. 30, 2017	898,117	$ 569,302	463,250	(22,222)	$ (112,213)
Beginning Balances (in shares) at Dec. 31, 2017		68,730,731			(6,661,644)
Beginning Balances at Dec. 31, 2017	930,664	$ 573,109	491,847	(20,390)	$ (113,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66,924		66,924
Reclassification from AOCI, Current Period, Tax	0		4,942	(4,942)
Other comprehensive income (loss)	(17,676)			(17,676)
Cash dividends declared :
Common stock at $0.38 per share in 2018 and $0.34 per share in 2017	(30,394)		(30,394)
Stock Issued During Period, Shares, New Issues		35,551,063
Stock Issued During Period, Value, Acquisitions	1,045,876	$ 1,045,876
Stock Options and Warrants Acquired And Converted Pursuant To Acquisition	16,037	16,037
Stock Issued During Period, Shares, Other					53,907
Adjustments to Additional Paid in Capital, Other	0	(922)			$ 922
Exercise of stock options, net of shares purchased (in shares)					31,554
Exercise of stock options, net of shares purchased	267	(275)			$ 542
Restricted stock awards, net of forfeitures (in shares)					199,286
Restricted stock awards, net of forfeitures	(2,207)	(4,699)			$ 2,492
Share-based compensation expense	3,446	$ 3,446
Ending Balances (in shares) at Jun. 30, 2018		104,281,794			(6,376,897)
Ending Balances at Jun. 30, 2018	$ 2,012,937	$ 1,632,572	$ 533,319	$ (43,008)	$ (109,946)

CONSOLIDATED STATEMENTS OF CHA7

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS EQUITY (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Common Stock, Dividends, Per Share, Declared	$ 0.19	$ 0.17	$ 0.38	$ 0.34

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities
Net income	$ 36,418	$ 66,924	$ 47,150
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan and lease losses		6,038	834
Depreciation and amortization		10,208	6,354
Stock-based compensation expense		3,446	2,966
Pension expense (income)	338	182	(637)
Net amortization (accretion) on investment securities		5,178	4,998
Net (gains) losses on sales of investment securities		30	(1,354)
Originations of loans held for sale		(54,041)	(75,543)
Net gains from sales of loans held for sale	(2,316)	(2,904)	(2,543)
Proceeds from sales of loans held for sale		50,004	78,771
Deferred income taxes		(12,104)	3,987
Decrease (increase) cash surrender value of life insurance		(398)	116
Decrease (increase) in interest receivable		(565)	(1,397)
Decrease (increase) in indemnification asset		(1,900)	(2,418)
(Decrease) increase in interest payable		2,596	148
Decrease (increase) in other assets		26,646	(18,472)
(Decrease) increase in other liabilities		10,724	(5,571)
Net cash provided by (used in) operating activities		114,660	41,993
Investing activities
Proceeds from sales of securities available-for-sale		216,197	125,606
Proceeds from calls, paydowns and maturities of securities available-for-sale		161,733	102,893
Purchases of securities available-for-sale		(444,686)	(464,543)
Proceeds from calls, paydowns and maturities of securities held-to-maturity		26,834	72,078
Payments to Acquire Held-to-maturity Securities		14,014	14,441
Net decrease (increase) in interest-bearing deposits with other banks		(3,941)	52,611
Net decrease (increase) in loans and leases		(83,617)	(121,944)
Proceeds from disposal of other real estate owned	618	2,840	2,292
Purchases of premises and equipment		(13,662)	(4,247)
Net cash (paid) acquired from business combinations		64,887	0
Net cash paid for branch divestitures		(41,197)
Net cash provided by (used in) investing activities		(128,626)	(249,695)
Financing activities
Net (decrease) increase in total deposits		(55,757)	(56,879)
Net (decrease) increase in short-term borrowings		178,143	280,421
Payments of long-term debt		51,985	0
Proceeds from FHLB borrowings		50,000	0
Cash dividends paid on common stock		(40,685)	(20,243)
Proceeds from exercise of stock options		267	283
Net cash provided by (used in) financing activities		79,983	203,582
Cash and due from banks:
Change in cash and due from banks		66,017	(4,120)
Cash and due from banks at beginning of period		150,650	121,598	$ 121,598
Cash and due from banks at end of period	216,667	216,667	117,478	150,650
Supplemental schedule for investing activities
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Assets, Net Of Purchase Consideration	3,328,802	3,328,802		0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	$ 4,007,743	4,007,743		0
Goodwill		$ 678,941	$ 0	$ 0

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The Consolidated Financial Statements of First Financial Bancorp., a financial holding company principally serving Ohio, Indiana, Kentucky and Illinois, include the accounts and operations of First Financial and its wholly-owned subsidiary, First Financial Bank. All significant intercompany transactions and accounts have been eliminated in consolidation. Certain reclassifications of prior periods' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings. The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes. These estimates, assumptions and judgments are inherently subjective and may be susceptible to significant change. Actual realized amounts could differ materially from these estimates. These interim financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X, and serve to update the Form 10-K for the year ended December 31, 2017 . These interim financial statements may not include all information and notes necessary to constitute a complete set of financial statements under GAAP applicable to annual periods and it is suggested that these interim statements be read in conjunction with the Form 10-K. Management believes these unaudited consolidated financial statements reflect all adjustments of a normal recurring nature which are necessary for a fair presentation of the results for the interim periods presented. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. The Consolidated Balance Sheet as of December 31, 2017 has been derived from the audited financial statements in the Company’s 2017

RECENTLY ADOPTED AND ISSUED ACC

RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS	6 Months Ended
	Jun. 30, 2018
Recently Adopted and Issued Accounting Standards [Abstract]
Recently Adopted and Issued Accounting Standards Disclosure [Text Block]	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. For further detail, see Note 13 – Revenue Recognition. 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. This update also requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes. The guidance in this ASU became effective in the first quarter of 2018 and did not have a material impact on the Consolidated Financial Statements. In accordance with the guidance, the Company measured the fair value of its financial instruments as of June 30, 2018 using an exit price notion. For further detail, see Note 15 – Fair Value Disclosures. 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 June 30, 2018 , 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 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 management committee and engaged a third party vendor to assist with the transition to the guidance set forth in this update. The committee is currently evaluating the impact of this update on First Financial’s 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 became effective in the first quarter of 2018 and did not have a material impact on the 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 became effective in the first quarter of 2018 and did not have a material impact on the Consolidated Financial Statements. 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 became effective in the first quarter of 2018 and did not have a material impact on the 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, and 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 is 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. First Financial early adopted the provisions set forth in this update in the first quarter of 2018, and as a result, reclassified $4.9 million

INVESTMENTS

INVESTMENTS	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	INVESTMENTS For the three and six months ended June 30, 2018, proceeds on the sale of $216.2 million of available-for-sale securities, and resulted in insignificant gross gains and losses. For the three months ended June 30, 2017, proceeds on the sale of $103.4 million of available-for-sale securities resulted in gains of $1.0 million and losses of $0.1 million . For the six months ended June 30, 2017 , proceeds on the sale of $125.6 million of available-for-sale securities resulted in gains of $1.5 million and losses of $0.1 million . In addition to the sale of certain securities during the second quarter 2018, First Financial reclassified $367.9 million of held-to-maturity securities to available-for-sale to align with post-merger investment strategies. The following is a summary of held-to-maturity and available-for-sale investment securities as of June 30, 2018 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized Unrecognized gain Unrecognized loss Fair Amortized cost Unrealized gain Unrealized loss Fair U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (3 ) $ 95 Securities of U.S. government agencies and corporations 0 0 0 0 34,896 84 (452 ) 34,528 Mortgage-backed securities - residential 31,857 0 (1,515 ) 30,342 644,358 1,314 (10,152 ) 635,520 Mortgage-backed securities - commercial 152,906 13 (5,503 ) 147,416 290,930 106 (5,059 ) 285,977 Collateralized mortgage obligations 13,982 0 (675 ) 13,307 873,923 965 (10,313 ) 864,575 Obligations of state and other political subdivisions 245,212 936 (1,428 ) 244,720 250,993 2,214 (1,910 ) 251,297 Asset-backed securities 0 0 0 0 492,702 879 (1,354 ) 492,227 Other securities 0 0 0 0 89,357 1,938 (605 ) 90,690 Total $ 443,957 $ 949 $ (9,121 ) $ 435,785 $ 2,677,257 $ 7,500 $ (29,848 ) $ 2,654,909 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 Unrecognized gain 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 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 table provides a summary of investment securities by contractual maturity as of June 30, 2018 , 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 By Contractual Maturity: Due in one year or less $ 0 $ 0 $ 4,125 $ 4,123 Due after one year through five years 275 279 70,801 70,802 Due after five years through ten years 15,799 15,778 140,577 142,222 Due after ten years 229,138 228,663 159,841 159,463 Mortgage-backed securities - residential 31,857 30,342 644,358 635,520 Mortgage-backed securities - commercial 152,906 147,416 290,930 285,977 Collateralized mortgage obligations 13,982 13,307 873,923 864,575 Asset-backed securities 0 0 492,702 492,227 Total $ 443,957 $ 435,785 $ 2,677,257 $ 2,654,909 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 June 30, 2018 or December 31, 2017 . As of June 30, 2018 , the Company's investment securities portfolio consisted of 1,385 securities, of which 656 were in an unrealized loss position. As of December 31, 2017, the Company's investment securities portfolio consisted of 775 securities, of which 237 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: June 30, 2018 Less than 12 months 12 months or more Total (Dollars in thousands) Fair value Unrealized loss Fair Unrealized Fair Unrealized U.S. Treasuries $ 95 $ (3 ) $ 0 $ 0 $ 95 $ (3 ) Securities of U.S. Government agencies and corporations 19,890 (311 ) 5,379 (141 ) 25,269 (452 ) Mortgage-backed securities - residential 488,725 (5,650 ) 129,218 (6,017 ) 617,943 (11,667 ) Mortgage-backed securities - commercial 278,366 (5,414 ) 88,624 (5,148 ) 366,990 (10,562 ) Collateralized mortgage obligations 628,667 (6,910 ) 99,142 (4,078 ) 727,809 (10,988 ) Obligations of state and other political subdivisions 186,269 (2,195 ) 27,441 (1,143 ) 213,710 (3,338 ) Asset-backed securities 219,064 (1,215 ) 13,591 (139 ) 232,655 (1,354 ) Other securities 17,299 (226 ) 7,571 (379 ) 24,870 (605 ) Total $ 1,838,375 $ (21,924 ) $ 370,966 $ (17,045 ) $ 2,209,341 $ (38,969 ) December 31, 2017 Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized (Dollars in thousands) value loss value loss value 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 )

LOANS AND LEASES

LOANS AND LEASES	6 Months Ended
	Jun. 30, 2018
Receivables [Abstract]
LOANS AND LEASES	LOANS AND LEASES First Financial offers clients a variety of commercial and consumer loan and lease products with distinct interest rates and payment terms. Commercial loan categories include C&I, CRE, 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, Kentucky and Illinois). 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. 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 of 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 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 previously described are derived from standard regulatory rating definitions and are assigned upon initial approval of credit to borrowers and updated periodically thereafter. First Financial considers repayment performance to be 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 assets 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 June 30, 2018 Commercial Real Estate Lease (Dollars in thousands) & industrial Construction Commercial financing Total Pass $ 2,367,649 $ 543,479 $ 3,794,902 $ 94,763 $ 6,800,793 Special Mention 24,261 11,947 29,399 0 65,607 Substandard 48,686 42 64,692 1,435 114,855 Doubtful 0 0 0 0 0 Total $ 2,440,596 $ 555,468 $ 3,888,993 $ 96,198 $ 6,981,255 (Dollars in thousands) Residential real estate Home equity Installment Credit card Total Performing $ 905,649 $ 828,558 $ 100,422 $ 48,665 $ 1,883,294 Nonperforming 13,255 6,473 304 0 20,032 Total $ 918,904 $ 835,031 $ 100,726 $ 48,665 $ 1,903,326 As of December 31, 2017 Commercial Real Estate Lease (Dollars in thousands) & industrial Construction Commercial 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 (Dollars in thousands) 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 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 date of the scheduled payment. Loan delinquency, including loans classified as nonaccrual, was as follows: As of June 30, 2018 (Dollars in thousands) 30 – 59 60 – 89 > 90 days Total Current Subtotal Purchased impaired Total > 90 days Loans Commercial & industrial $ 1,885 $ 389 $ 2,814 $ 5,088 $ 2,429,204 $ 2,434,292 $ 6,304 $ 2,440,596 $ 0 Lease financing 0 0 0 0 96,198 96,198 0 96,198 0 Construction real estate 447 0 0 447 554,754 555,201 267 555,468 0 Commercial real estate 3,291 1,829 15,999 21,119 3,803,534 3,824,653 64,340 3,888,993 16 Residential real estate 1,962 601 2,945 5,508 872,404 877,912 40,992 918,904 0 Home equity 3,834 750 3,443 8,027 822,359 830,386 4,645 835,031 0 Installment 165 22 263 450 99,669 100,119 607 100,726 0 Credit card 427 216 311 954 47,711 48,665 0 48,665 311 Total $ 12,011 $ 3,807 $ 25,775 $ 41,593 $ 8,725,833 $ 8,767,426 $ 117,155 $ 8,884,581 $ 327 As of December 31, 2017 (Dollars in thousands) 30 – 59 60 – 89 > 90 days Total Current Subtotal Purchased impaired Total > 90 days Loans Commercial & 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 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 205 TDRs totaling $27.8 million at June 30, 2018 , including $21.8 million on accrual status and $5.9 million 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 $1.1 million related to TDRs at June 30, 2018 . For each of the three and six month periods ended June 30, 2018 and 2017, the Company charged off $0.1 million for the portion of TDRs determined to be uncollectible. Additionally, as of June 30, 2018 , $13.1 million of accruing TDRs have been performing in accordance with the restructured terms for more than one year. 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 classified as nonaccrual. First Financial had an insignificant amount of commitments outstanding to lend additional funds to borrowers whose loan terms had been modified through TDRs. At December 31, 2017 , the ALLL included reserves of $1.3 million related to TDRs, and $17.2 million of the accruing TDRs had been performing in accordance with the restructured terms for more than one year. The following tables provide information on loan modifications classified as TDRs during the three and six months ended June 30, 2018 and 2017 : Three months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial & industrial 8 $ 6,221 $ 6,183 4 $ 2,177 $ 2,183 Construction real estate 0 0 0 0 0 0 Commercial real estate 4 2,047 2,016 6 1,506 1,449 Residential real estate 1 201 201 0 0 0 Home equity 0 0 0 0 0 0 Installment 0 0 0 0 0 0 Total 13 $ 8,469 $ 8,400 10 $ 3,683 $ 3,632 Six months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial & industrial 12 $ 7,149 $ 7,096 6 $ 5,679 $ 5,624 Construction real estate 0 0 0 0 0 0 Commercial real estate 6 2,119 2,088 6 1,506 1,449 Residential real estate 3 294 294 0 0 0 Home equity 0 0 0 0 0 0 Installment 0 0 0 0 0 0 Total 21 $ 9,562 $ 9,478 12 $ 7,185 $ 7,073 The following table provides information on how TDRs were modified during the three and six months ended June 30, 2018 and 2017 : Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Extended maturities $ 2,000 $ 2,587 $ 2,888 $ 3,261 Adjusted interest rates 0 0 52 2,767 Combination of rate and maturity changes 0 180 0 180 Forbearance 6,199 827 6,199 827 Other (1) 201 38 339 38 Total $ 8,400 $ 3,632 $ 9,478 $ 7,073 (1) 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 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. There was one TDR, insignificant in amount, for which there was a payment default during the period that occurred within twelve months of the loan modification for the three and six months ended June 30, 2018 . There were no TDRs for which there was a payment default during the period that occurred within twelve months of the loan modification for the three or six month periods ended June 30, 2017 . 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: (Dollars in thousands) June 30, 2018 December 31, 2017 Impaired loans Nonaccrual loans (1) Commercial & industrial $ 3,448 $ 5,229 Lease financing 0 82 Construction real estate 24 29 Commercial real estate 21,593 10,616 Residential real estate 9,278 4,140 Home equity 5,820 3,743 Installment 299 243 Nonaccrual loans 40,462 24,082 Accruing troubled debt restructurings 21,839 17,545 Total impaired loans $ 62,301 $ 41,627 (1) Nonaccrual loans include nonaccrual TDRs of $5.9 million and $6.4 million as of June 30, 2018 and December 31, 2017 , respectively. Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Interest income effect on impaired loans Gross amount of interest that would have been recorded under original terms $ 1,132 $ 1,158 $ 1,934 $ 1,974 Interest included in income Nonaccrual loans 146 163 226 305 Troubled debt restructurings 189 169 313 395 Total interest included in income 335 332 539 700 Net impact on interest income $ 797 $ 826 $ 1,395 $ 1,274 First Financial individually reviews all impaired commercial loan relationships, 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, 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 was as follows: As of June 30, 2018 As of December 31, 2017 (Dollars in thousands) Current balance Contractual principal balance Related allowance Current balance Contractual Related Loans with no related allowance recorded Commercial & industrial $ 10,856 $ 14,647 $ 0 $ 7,162 $ 8,460 $ 0 Lease financing 0 0 0 82 82 0 Construction real estate 24 57 0 29 60 0 Commercial real estate 30,655 36,421 0 18,423 20,837 0 Residential real estate 12,216 14,383 0 6,876 8,145 0 Home equity 6,372 7,311 0 4,356 5,399 0 Installment 304 603 0 255 422 0 Total 60,427 73,422 0 37,183 43,405 0 Loans with an allowance recorded Commercial & industrial 379 379 179 169 169 169 Lease financing 0 0 0 0 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 356 356 25 3,119 3,120 448 Residential real estate 1,039 1,039 160 1,056 1,063 160 Home equity 100 100 2 100 100 2 Installment 0 0 0 0 0 0 Total 1,874 1,874 366 4,444 4,452 779 Total Commercial & industrial 11,235 15,026 179 7,331 8,629 169 Lease financing 0 0 0 82 82 0 Construction real estate 24 57 0 29 60 0 Commercial real estate 31,011 36,777 25 21,542 23,957 448 Residential real estate 13,255 15,422 160 7,932 9,208 160 Home equity 6,472 7,411 2 4,456 5,499 2 Installment 304 603 0 255 422 0 Total $ 62,301 $ 75,296 $ 366 $ 41,627 $ 47,857 $ 779 First Financial's average impaired loans by class and interest income recognized by class was as follows: Three months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Average Interest Average Interest Loans with no related allowance recorded Commercial & industrial $ 9,714 $ 73 $ 17,198 $ 87 Lease financing 0 0 98 1 Construction real estate 25 1 1,075 0 Commercial real estate 27,516 140 25,465 144 Residential real estate 9,173 76 7,605 46 Home equity 5,222 27 3,926 27 Installment 305 1 357 1 Total 51,955 318 55,724 306 Loans with an allowance recorded Commercial & industrial 309 6 2,301 11 Lease financing 0 0 0 0 Construction real estate 0 0 0 0 Commercial real estate 358 3 658 8 Residential real estate 1,042 7 1,126 6 Home equity 101 1 101 1 Installment 0 0 0 0 Total 1,810 17 4,186 26 Total Commercial & industrial 10,023 79 19,499 98 Lease financing 0 0 98 1 Construction real estate 25 1 1,075 0 Commercial real estate 27,874 143 26,123 152 Residential real estate 10,215 83 8,731 52 Home equity 5,323 28 4,027 28 Installment 305 1 357 1 Total $ 53,765 $ 335 $ 59,910 $ 332 Six months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Average Interest Average Interest Loans with no related allowance recorded Commercial & industrial $ 8,863 $ 99 $ 15,607 $ 196 Lease financing 27 0 149 2 Construction real estate 26 2 538 0 Commercial real estate 24,485 239 19,939 304 Residential real estate 8,407 123 8,032 92 Home equity 4,933 47 4,111 51 Installment 288 1 413 3 Total 47,029 511 48,789 648 Loans with an allowance recorded Commercial & industrial 262 6 1,094 24 Lease financing 0 0 0 0 Construction real estate 0 0 0 0 Commercial real estate 1,278 6 4,374 13 Residential real estate 1,047 14 1,185 13 Home equity 100 2 101 2 Installment 0 0 0 0 Total 2,687 28 6,754 52 Total Commercial & industrial 9,125 105 16,701 220 Lease financing 27 0 149 2 Construction real estate 26 2 538 0 Commercial real estate 25,763 245 24,313 317 Residential real estate 9,454 137 9,217 105 Home equity 5,033 49 4,212 53 Installment 288 1 413 3 Total $ 49,716 $ 539 $ 55,543 $ 700 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. First Financial had purchased impaired loans totaling $117.2 million at June 30, 2018 , which included $24.1 million acquired in the merger with MSFG. Accretable yield, or income expected to be collected, and nonaccretable yield on the purchase impaired loans acquired in the MSFG merger was $1.2 million and $2.7 million , respectively, on the date of acquisition. First Financial had $105.0 million of purchased impaired loans at December 31, 2017 . 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. In its merger with MSFG, First Financial acquired loans with a fair value of $2.7 billion and gross contractual amounts receivable of $2.9 billion on the date of acquisition that were accounted for in accordance with FASB ASC Topic 310-20. OREO. 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. Changes in OREO were as follows: Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Balance at beginning of period $ 1,065 $ 5,300 $ 2,781 $ 6,284 Additions Commercial & industrial 1,020 50 1,190 172 Residential real estate 525 1,913 984 2,078 Total additions 1,545 1,963 2,174 2,250 Disposals Commercial & industrial (326 ) (682 ) (2,430 ) (1,607 ) Residential real estate (292 ) (448 ) (410 ) (685 ) Total disposals (618 ) (1,130 ) (2,840 ) (2,292 ) Valuation adjustment Commercial & industrial 0 (116 ) (97 ) (162 ) Residential real estate (139 ) (56 ) (165 ) (119 ) Total valuation adjustment (139 ) (172 ) (262 ) (281 ) Balance at end of period $ 1,853 $ 5,961 $ 1,853 $ 5,961

ALLOWANCE FOR LOAN AND LEASE LO

ALLOWANCE FOR LOAN AND LEASE LOSSES	6 Months Ended
	Jun. 30, 2018
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. 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. Changes in the ALLL by loan category were as follows: Three months ended June 30, 2018 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 period $ 18,038 $ 626 $ 4,267 $ 20,321 $ 4,727 $ 4,828 $ 290 $ 1,283 $ 54,380 Provision for loan and lease losses 3,328 170 (282 ) (619 ) (28 ) 171 136 859 3,735 Gross charge-offs (4,356 ) 0 0 (78 ) (101 ) (385 ) (218 ) (684 ) (5,822 ) Recoveries 518 1 0 887 70 187 82 38 1,783 Total net charge-offs (3,838 ) 1 0 809 (31 ) (198 ) (136 ) (646 ) (4,039 ) Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 Three months ended June 30, 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 period $ 17,148 $ 616 $ 3,607 $ 23,745 $ 5,485 $ 3,774 $ 419 $ 1,532 $ 56,326 Provision for loan and lease losses 3,537 (67 ) (280 ) (2,941 ) (305 ) 526 19 (22 ) 467 Loans charged off (3,065 ) 0 0 (485 ) (223 ) (384 ) (126 ) (215 ) (4,498 ) Recoveries 693 1 89 1,398 59 222 43 73 2,578 Total net charge-offs (2,372 ) 1 89 913 (164 ) (162 ) (83 ) (142 ) (1,920 ) Ending allowance for loan and lease losses $ 18,313 $ 550 $ 3,416 $ 21,717 $ 5,016 $ 4,138 $ 355 $ 1,368 $ 54,873 Six months ended June 30, 2018 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Allowance for loan and lease losses: Balance at beginning of period $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 Provision for loan and lease losses 4,217 121 408 196 86 (123 ) 87 1,046 6,038 Loans charged off (5,241 ) 0 0 (2,254 ) (197 ) (627 ) (234 ) (938 ) (9,491 ) Recoveries 954 1 0 1,639 96 616 130 72 3,508 Total net charge-offs (4,287 ) 1 0 (615 ) (101 ) (11 ) (104 ) (866 ) (5,983 ) Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 As of June 30, 2018 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance balance attributable to loans Individually evaluated for impairment $ 179 $ 0 $ 0 $ 25 $ 160 $ 2 $ 0 $ 0 $ 366 Collectively evaluated for impairment 17,349 797 3,985 20,486 4,508 4,799 290 1,496 53,710 Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 Loans Individually evaluated for impairment $ 11,235 $ 0 $ 24 $ 31,011 $ 13,255 $ 6,472 $ 304 $ 0 $ 62,301 Collectively evaluated for impairment 2,429,361 96,198 555,444 3,857,982 905,649 828,559 100,422 48,665 8,822,280 Total loans $ 2,440,596 $ 96,198 $ 555,468 $ 3,888,993 $ 918,904 $ 835,031 $ 100,726 $ 48,665 $ 8,884,581 Six months ended June 30, 2017 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Allowance for loan and lease losses: Balance at beginning of period $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Provision for loan and lease losses 2,941 (167 ) 45 (5,507 ) 2,024 1,331 28 139 834 Loans charged off (4,808 ) 0 0 (970 ) (284 ) (564 ) (175 ) (447 ) (7,248 ) Recoveries 955 1 89 1,654 68 328 114 117 3,326 Total net charge-offs (3,853 ) 1 89 684 (216 ) (236 ) (61 ) (330 ) (3,922 ) Ending allowance for loan and lease losses $ 18,313 $ 550 $ 3,416 $ 21,717 $ 5,016 $ 4,138 $ 355 $ 1,368 $ 54,873 As of December 31, 2017 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance balance attributable to loans Individually evaluated for impairment $ 169 $ 0 $ 0 $ 448 $ 160 $ 2 $ 0 $ 0 $ 779 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 Individually evaluated for impairment $ 7,331 $ 82 $ 29 $ 21,542 $ 7,932 $ 4,456 $ 255 $ 0 $ 41,627 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

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2018
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 the second quarter of 2018, First Financial recorded additions to goodwill resulting from the merger with MSFG. No additions to goodwill were recorded during 2017. For further detail on the merger with MSFG, see Note 16 - Business Combinations. Changes in the carrying amount of goodwill for the six months ended June 30, 2018 and the year ended December 31, 2017 were as follows: (Dollars in thousands) June 30, December 31, Balance at beginning of year $ 204,084 $ 204,084 Goodwill resulting from business combinations 678,941 0 Balance at end of period $ 883,025 $ 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 most recent annual impairment test as of October 1, 2017 and no impairment was indicated. As of June 30, 2018 , 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 June 30, 2018 and December 31, 2017 , First Financial had $51.6 million and $5.3 million , respectively, of other intangible assets included in Goodwill and other intangibles in the Consolidated Balance Sheets, which primarily consist of core deposit intangibles. Core deposit intangibles represent the estimated fair value of acquired customer deposit relationships on the date of acquisition and are amortized on an accelerated basis over their estimated useful lives. Core deposit intangibles were $42.5 million and $3.3 million as of June 30, 2018 and December 31, 2017 , respectively. First Financial's core deposit intangibles have an estimated weighted average remaining life of 9.3 years . Amortization expense recognized on intangible assets for the three months ended June 30, 2018 and 2017 was $2.4 million and $0.3 million , respectively. Amortization expense recognized on intangible assets for the six months ended June 30, 2018 and 2017 was $2.6 million and $0.7 million

BORROWINGS

BORROWINGS	6 Months Ended
	Jun. 30, 2018
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. To secure its liability to the client, the Bank is authorized to sell or repurchase U.S. Treasury, government agency and mortgage-backed securities. First Financial had $1.1 billion in short-term borrowings with the FHLB at June 30, 2018 and $742.3 million as of December 31, 2017 . These short-term borrowings are used to manage normal liquidity needs and support the Company's asset and liability management strategies. First Financial has a $15.0 million short-term credit facility with an unaffiliated bank that matured in July 2018, but is in the process of being extended. This facility can have a variable or fixed interest rate and provides First Financial additional liquidity, if needed, for various corporate activities including the repurchase of First Financial common stock and the payment of dividends to shareholders. As of June 30, 2018 and December 31, 2017 , 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 June 30, 2018 and December 31, 2017 . In conjunction with its merger with MSFG, First Financial acquired certain variable rate short-term borrowings with an unaffiliated bank. As of June 30, 2018, the balance outstanding was $8.3 million and the interest rate was 4.19% . This term debt is paid quarterly and matures in 2019. First Financial had $469.4 million and $119.7 million of long-term debt as of June 30, 2018 and December 31, 2017, respectively, which included subordinated notes, FHLB long term advances and an interest free loan with a municipality. The following is a summary of First Financial's long-term debt: June 30, 2018 December 31, 2017 (Dollars in thousands) Amount Average rate Amount Average rate Subordinated notes $ 177,887 5.13 % $ 120,000 5.13 % Unamortized discount and debt issuance costs (8,819 ) N/A (1,362 ) N/A FHLB borrowings 299,580 1.90 % 241 1.09 % Capital loan with municipality 775 0.00 % 775 0.00 % Total long-term debt $ 469,423 3.16 % $ 119,654 5.14 % In 2015, First Financial issued $120.0 million of subordinated notes, which have a fixed interest rate of 5.125% payable semiannually and mature on August 25, 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. In addition, First Financial acquired, $49.5 million of variable rate subordinated notes in the MSFG merger that was issued to previously formed trusts in exchange for the trust proceeds. Interest on the acquired subordinated notes is payable quarterly, in arrears, and the Company has the option to defer interest payments for a period not to exceed 20 consecutive quarters. The acquired subordinated notes mature 30 years from issuance and may be called at par at any point following the 5 years anniversary of issuance. First Financial also acquired $8.4 million of 6.95% fixed rate private placement subordinated debt in conjunction with the MSFG merger that matures in 2025. In addition to subordinated notes, long-term debt included $299.6 million and $0.2 million of fixed rate FHLB long-term advances as of June 30, 2018 and December 31, 2017 , respectively. As of June 30, 2018, these long-term advances had a weighted average interest rate of 1.90%

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
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 incom e and reclassifications out of accumulated other comprehensive income (loss) are as follows: Three months ended June 30, 2018 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Reclass from Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ (11,456 ) $ (30 ) $ (11,426 ) $ 2,448 $ (8,978 ) $ (10,051 ) $ (8,978 ) $ (19,029 ) Unrealized gain (loss) on derivatives 203 0 203 (44 ) 159 (545 ) 159 (386 ) Retirement obligation 0 (452 ) 452 42 494 (24,087 ) 494 (23,593 ) Total $ (11,253 ) $ (482 ) $ (10,771 ) $ 2,446 $ (8,325 ) $ (34,683 ) $ (8,325 ) $ (43,008 ) Three months ended June 30, 2017 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Reclass from Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 7,170 $ 838 $ 6,332 $ (2,256 ) $ 4,076 $ (3,062 ) $ 4,076 $ 1,014 Unrealized gain (loss) on derivatives 202 0 202 (74 ) 128 (963 ) 128 (835 ) Retirement obligation 0 (335 ) 335 (122 ) 213 (22,614 ) 213 (22,401 ) Total $ 7,372 $ 503 $ 6,869 $ (2,452 ) $ 4,417 $ (26,639 ) $ 4,417 $ (22,222 ) Six months ended June 30, 2018 Total other comprehensive income Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Pre-tax Tax effect Net of tax Beginning Balance Net Activity Reclass of Stranded Tax Effects Ending Balance Unrealized gain (loss) on investment securities $ (23,992 ) $ (30 ) $ (23,962 ) $ 5,154 $ (18,808 ) $ (182 ) $ (18,808 ) $ (39 ) $ (19,029 ) Unrealized gain (loss) on derivatives 405 0 405 (90 ) 315 (577 ) 315 (124 ) (386 ) Retirement obligation 0 (871 ) 871 (54 ) 817 (19,631 ) 817 (4,779 ) (23,593 ) Total $ (23,587 ) $ (901 ) $ (22,686 ) $ 5,010 $ (17,676 ) $ (20,390 ) $ (17,676 ) $ (4,942 ) $ (43,008 ) Six months ended June 30, 2017 Total other comprehensive income Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 10,002 $ 1,354 $ 8,648 $ (3,085 ) $ 5,563 $ (4,549 ) $ 5,563 $ 1,014 Unrealized gain (loss) on derivatives 405 0 405 (149 ) 256 (1,091 ) 256 (835 ) Retirement obligation 0 (670 ) 670 (268 ) 402 (22,803 ) 402 (22,401 ) Total $ 10,407 $ 684 $ 9,723 $ (3,502 ) $ 6,221 $ (28,443 ) $ 6,221 $ (22,222 ) The following table presents the activity reclassified from accumulated other comprehensive income into income during the three and six month periods ended June 30, 2018 and 2017, respectively: Amount reclassified from accumulated other comprehensive income (1) Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Affected Line Item in the Consolidated Statements of Income Realized gain (loss) on securities available-for-sale $ (30 ) $ 838 $ (30 ) $ 1,354 Net gain (loss) on sales of investments securities Defined benefit pension plan Amortization of prior service cost (2) 103 104 206 207 Other noninterest expense (2018) Salaries and employee benefits (2017) Recognized net actuarial loss (2) (555 ) (439 ) (1,077 ) (877 ) Other noninterest expense (2018) Defined benefit pension plan total (452 ) (335 ) (871 ) (670 ) Total reclassifications for the period, before tax $ (482 ) $ 503 $ (901 ) $ 684 (1) Negative amounts are reductions to net income. (2)

DERIVATIVES

DERIVATIVES	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	DERIVATIVES First Financial uses certain derivative instruments, including interest 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. First Financial primarily utilizes interest rate swaps as a means to offer borrowers credit-based products that meet their needs. First Financial 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 established in the interest rate 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 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 June 30, 2018 , the Company had a total counterparty notional amount outstanding of $1.2 billion , spread among fourteen counterparties, with an outstanding asset from these contracts of $21.8 million . 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 . 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 classification and amounts recognized in the Consolidated Balance Sheets for client derivatives: June 30, 2018 December 31, 2017 Estimated fair value Estimated fair value (Dollars in thousands) Balance sheet classification Notional amount Gain Loss Notional amount Gain Loss Client derivatives - instruments associated with loans Matched interest rate swaps with borrower Accrued interest and other assets $ 1,179,156 $ 3,261 $ (24,306 ) $ 837,040 $ 7,153 $ (5,529 ) Matched interest rate swaps with counterparty Accrued interest and other liabilities 1,179,156 24,306 (3,259 ) 837,040 5,529 (7,158 ) Total $ 2,358,312 $ 27,567 $ (27,565 ) $ 1,674,080 $ 12,682 $ (12,687 ) In connection with its use of derivative instruments, First Financial and its counterparties may be required to post cash collateral to offset the market position of the derivative instruments. 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 client derivative liabilities recognized in the Consolidated Balance Sheets: June 30, 2018 December 31, 2017 (Dollars in thousands) Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of liabilities presented in the Consolidated Balance Sheets Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of liabilities presented in the Consolidated Balance Sheets Client derivatives Matched interest rate swaps with counterparty $ 27,567 $ (7,152 ) $ 20,415 $ 12,687 $ 2,279 $ 14,966 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 June 30, 2018 : 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 $ 1,179,156 4.8 $ (21,045 ) 4.50 % 4.25 % Pay fixed, matched interest rate swaps with counterparty 1,179,156 4.8 21,047 4.25 % 4.50 % Total client derivatives $ 2,358,312 4.8 $ 2 4.37 % 4.37 % 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 $146.3 million as of June 30, 2018 and $95.9 million as of December 31, 2017 . The fair value of these agreements is recorded in Accrued interest and other liabilities on the Consolidated Balance Sheets and was $0.1 million at both June 30, 2018 and December 31, 2017 . 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 loans held for sale. At June 30, 2018 , the notional amount of the IRLCs was $37.2 million and the notional amount of forward commitments was $35.6 million . As of December 31, 2017 , the notional amount of IRLCs was $12.3 million and the notional amount of forward commitments was $15.4 million . The fair value of these agreements was insignificant at both June 30, 2018 and $0.1 million December 31, 2017

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES First Financial offers a variety of financial instruments including standby letters of credit and outstanding commitments to extend credit to assist clients in meeting their requirement for liquidity and credit enhancement. GAAP does not require these financial instruments to be recorded in the Consolidated Financial Statements. First Financial utilizes the same credit policies in issuing commitments and conditional obligations as it does for credit instruments recorded on the Consolidated Balance Sheets. First Financial’s exposure to credit loss in the event of nonperformance by the counterparty 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 incurred losses inherent in letters of credit and outstanding loan commitments and records the reserve within Accrued interest and other liabilities on the Consolidated Balance Sheets. First Financial had $1.1 million and $0.5 million of reserves for unfunded commitments as of June 30, 2018 and December 31, 2017 , respectively. Loan commitments. Loan commitments are agreements to extend credit to a client, absent any violation of conditions established in the commitment agreement. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments 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 $2.9 billion and $2.1 billion at June 30, 2018 and December 31, 2017 , respectively. As of June 30, 2018 , loan commitments with a fixed interest rate totaled $215.8 million while commitments with variable interest rates totaled $2.6 billion . At December 31, 2017 , loan commitments with a fixed interest rate totaled $44.3 million while commitments with variable interest rates totaled $2.0 billion . First Financial's fixed rate loan commitments have interest rates ranging from 0.00% to 21.00% and maturities ranging from less than 1 year to 30 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 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 issued letters of credit aggregating $35.6 million and $25.3 million at June 30, 2018 and December 31, 2017 , respectively. Management conducts regular reviews of these instruments on an individual client basis. Investments in affordable housing tax credits. First Financial has made 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. 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. First Financial's affordable housing commitments totaled $34.3 million and $35.9 million as of June 30, 2018 and December 31, 2017 , respectively. The Company recognized tax credits of $1.2 million and $0.8 million and $2.3 million and $1.6 million for the three months and six months ended June 30, 2018 and 2017 , respectively. The Company recognized amortization expense which was included in income tax expense of $1.6 million and $1.2 million for the three months ended June 30, 2018 and 2017 , respectively and $2.8 million and $2.2 million for the six months ended June 30, 2018 and 2017 , respectively. First Financial had no affordable housing contingent commitments as of June 30, 2018 or December 31, 2017 . 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 and are carried in Accrued interest and other assets on the Consolidated Balance Sheets. The Company’s recorded investment in these entities was approximately $2.9 million at June 30, 2018 and $3.0 million at December 31, 2017 . The maximum exposure to loss related to these investments was $2.9 million at June 30, 2018 and $3.0 million at December 31, 2017 , representing the Company’s investment balance and its unfunded commitments to invest additional amounts. Investments in historic tax credits resulted in $0.1 million of tax credits for each of the three months ended June 30, 2018 and 2017 , and $0.2 million and $0.3 million of tax credits for the six months ended June 30, 2018 and 2017 , respectively. Contingencies/Litigation. From time to time, First Financial and its subsidiaries may be engaged in various matters of litigation, other assertions of improper or fraudulent loan practices or lending violations and other matters. 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 are 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 June 30, 2018 . 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 June 30, 2018 or December 31, 2017

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES For the second quarter 2018 , income tax expense was $9.3 million , resulting in an effective tax rate of 20.4% compared with income tax expense of $11.2 million and an effective tax rate of 33.0% for the comparable period in 2017. For the first six months of 2018, income tax expense was $17.0 million , resulting in an effective tax rate of 20.2% compared with income tax expense of $21.7 million and an effective tax rate of 31.5% for the comparable period in 2017. On December 22, 2017, the Tax Cuts and Jobs Act was signed into law. As a result, First Financial valued its deferred tax assets and liabilities as well as its investments in affordable housing projects utilizing a 21% federal rate during the first half of 2018 compared to a 35% rate in the first half of 2017. ASU 2016-09, Compensation-Stock Compensation Improvements to Employee Share-Based Payment Accounting, requires the recognition of the income tax effects of share-based awards through the income statement as a component of income tax expense. First Financial recorded a $0.1 million tax benefit as a result of share awards vesting and exercised during the second quarter of 2018 and $0.5 million and $1.2 million for the first six months of 2018 and 2017, respectively. Tax benefits resulting from the vesting and exercise of share awards in the second quarter of 2017 were insignificant. At both June 30, 2018 and December 31, 2017 , First Financial had $2.9 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. The unrecognized tax benefits relate to state income tax exposures from taking tax positions where the Company believes it is likely that, upon examination, a state may take a position contrary to the position taken by First Financial. 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 June 30, 2018 and December 31, 2017 , 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 2017 remain open to examination by the federal taxing authority.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	6 Months Ended
	Jun. 30, 2018
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS 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 fixed income and publicly traded equity mutual funds. The pension plan does not directly own any shares of First Financial common stock or any other First Financial security or product. First Financial made no cash contributions to fund the pension plan during the six months ended June 30, 2018 , or the year ended December 31, 2017, and does not expect to make cash contributions to the plan through the remainder of 2018. As a result of the plan’s actuarial projections, which included consideration of the impact of the merger with MSFG, First Financial recorded expense of $0.3 million for the three months ended June 30, 2018 and $0.2 million for the six months ended June 30, 2018 . Conversely, First Financial recorded income of $0.3 million for the three months ended June 30, 2017 and $0.6 million for the six months ended June 30, 2017 . The following table sets forth information concerning amounts recognized in First Financial’s Consolidated Statements of Income related to the Company's pension plan: Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Service cost $ 1,735 $ 1,239 $ 3,030 $ 2,477 Interest cost 601 589 1,191 1,178 Expected return on assets (2,450 ) (2,481 ) (4,910 ) (4,962 ) Amortization of prior service cost (103 ) (104 ) (206 ) (207 ) Net actuarial loss 555 439 1,077 877 Net periodic benefit cost (income) $ 338 $ (318 ) $ 182 $ (637 )

REVENUE RECOGNITION

REVENUE RECOGNITION	6 Months Ended
	Jun. 30, 2018
Revenue Recognition [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION On January 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers using the modified retrospective method applied to all contracts not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under the guidance set forth in this update while prior period amounts continue to be reported in accordance with legacy GAAP. Adoption of this update did not result in a change to the accounting for any of the in-scope revenue streams. As such, no cumulative effect adjustment to retained earnings was recorded. The majority of the Company's revenues come from interest income and other sources, including loans, leases, securities and derivatives, that are outside the scope of this guidance. The Company's services that fall within the scope of this ASU are presented within Noninterest income and are recognized as revenue as the Company satisfies its obligation to the customer. Services within the scope of this guidance include service charges on deposits, wealth management fees, bankcard income, investment brokerage fees and the sale of OREO. Service charges on deposit accounts. The Company earns fees from its deposit customers for transaction-based, account maintenance and overdraft services. Transaction-based fees, which include services such as ATM use fees, stop payment charges, statement rendering and ACH fees, are recognized at the time the transaction is executed as that is the point in time the Company fulfills the customer's request. Account maintenance fees, which relate primarily to monthly maintenance, are earned over the course of a month, representing the period over which the Company satisfies the performance obligation. Similarly, overdraft fees are recognized at the point in time that the overdraft occurs as this corresponds with the Company's performance obligation. Service charges on deposit accounts are withdrawn from the customer's account balance. Trust and wealth management fees. Trust and wealth management fees are primarily asset-based, but can also include flat fees based upon a specific service rendered, such as tax preparation services. The Company’s performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end market value of the assets under management and the applicable fees. The Company does not earn performance-based incentives. Optional services such as real estate sales and tax return preparation services are also available to existing trust and wealth management customers. The Company’s performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, as incurred. Bankcard income. The Company earns interchange fees from cardholder transactions conducted through the Visa payment network. Interchange fees from cardholder transactions represent a percentage of the underlying transaction value and are recognized concurrent with the transaction processing services provided to the cardholder. Interchange income is presented on the Consolidated Statements of Income net of expenses. Gross interchange income for the second quarter of 2018 was $8.1 million , which was partially offset by $2.8 million of expenses within Noninterest income. Gross interchange income for the first six months of 2018 was $13.5 million , which was partially offset by $4.8 million of expenses. Gain/loss on sale of OREO. The Company records a gain or loss from the sale of OREO when control of the property transfers to the buyer, which generally occurs at the time of the executed deed. When the Company finances the sale of OREO to the buyer, the Company assesses whether the buyer is committed to perform their obligations under the contract and whether collectibility of the transaction price is probable. Once these criteria are met, the OREO asset is derecognized and the gain or loss on sale is recorded upon the transfer of control of the property to the buyer. Other. Other noninterest income consists of other recurring revenue streams such as transaction fees, safe deposit rental income, insurance commissions, merchant referral income and brokerage revenue. Transaction fees primarily include check printing sales commissions, collection fees and wire transfer fees which arise from in-branch transactions. Safe deposit rental income arises from services charged to the customer on an annual basis and recognized upon receipt of payment. Insurance commissions are agent commissions earned by the Company and earned upon the effective date of the bound coverage. Merchant referral income is associated with a program whereby the Company receives a share of processing revenue that is generated from clients that were referred by First Financial to the service provider. Revenue is recognized at the point in time when the transaction occurs. Brokerage revenue represents fees from investment brokerage services provided to customers by a third party provider. The Company receives commissions from the third-party service provider on a monthly basis based upon customer activity for the month. The fees are recognized monthly and a receivable is recorded until commissions are paid the following month. Because the Company (i) acts as an agent in arranging the relationship between the customer and the third-party service provider and (ii) does not control the services rendered to the customers, investment brokerage fees are presented net of related costs.

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	6 Months Ended
	Jun. 30, 2018
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: Three months ended Six months ended June 30, June 30, (Dollars in thousands, except per share data) 2018 2017 2018 2017 Numerator Net income available to common shareholders $ 36,418 $ 22,736 $ 66,924 $ 47,150 Denominator Basic earnings per common share - weighted average shares 97,347,533 61,543,478 79,599,709 61,471,347 Effect of dilutive securities Employee stock awards 545,374 625,031 504,914 649,706 Warrants 539,165 65,513 524,872 66,420 Diluted earnings per common share - adjusted weighted average shares 98,432,072 62,234,022 80,629,495 62,187,473 Earnings per share available to common shareholders Basic $ 0.37 $ 0.37 $ 0.84 $ 0.77 Diluted $ 0.37 $ 0.37 $ 0.83 $ 0.76 First Financial has two categories of warrants outstanding to purchase the Company's common stock as of June 30, 2018 . The first type of warrant represents the right to purchase one share of common stock, no par value per share, and has an exercise price of $12.11 per share. First Financial had warrants outstanding to purchase 22,698 and 112,233 shares of First Financial's common stock as of June 30, 2018 and 2017, respectively and these warrants expire in December of 2018. The second category of warrant was acquired in the MSFG merger and the Company had one such warrant outstanding as of June 30, 2018. This warrant represents the right to purchase 793,520 shares of First Financial's common stock at an exercise price of $10.72 per share and expires in January 2019. Stock options and warrants with exercise prices 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 end of period price of the Company's common shares, there were no antidilutive options at June 30, 2018 and June 30, 2017

FAIR VALUE DISCLOSURES

FAIR VALUE DISCLOSURES	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE DISCLOSURES	FAIR VALUE DISCLOSURES The fair value framework as disclosed in the Fair Value Topic includes a hierarchy which focuses on prioritizing the inputs used in valuation techniques. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), a lower priority to observable inputs other than quoted prices in active markets for identical assets and liabilities (Level 2) and the lowest priority to unobservable inputs (Level 3). When determining the fair value measurements for assets and liabilities, First Financial looks to active markets to price identical assets or liabilities whenever possible and classifies such items in Level 1. When identical assets and liabilities are not traded in active markets, First Financial looks to observable market data for similar assets and liabilities and classifies such items as Level 2. Certain assets and liabilities are not actively traded in observable markets and First Financial must use alternative techniques, based on unobservable inputs, to determine the fair value and classifies such items as Level 3. The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement. 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 June 30, 2018 Financial assets Cash and short-term investments $ 254,582 $ 254,582 $ 254,582 $ 0 $ 0 Investment securities held-to-maturity 443,957 435,785 0 435,785 0 Other investments 95,004 N/A N/A N/A N/A Loans held for sale 15,821 15,821 0 15,821 0 Loans and leases 8,830,505 8,847,519 0 0 8,847,519 Accrued interest receivable 40,152 40,152 0 13,939 26,213 Financial liabilities Deposits 10,103,747 10,073,140 0 10,073,140 0 Short-term borrowings 1,188,303 1,188,303 1,188,303 0 0 Long-term debt 469,423 462,478 0 462,478 0 Accrued interest payable 9,550 9,550 1,577 7,973 0 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 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 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 N/A = Not applicable The methods utilized to estimate the fair value of financial instruments at December 31, 2017 did not necessarily represent an exit price. In accordance with our adoption of ASU 2016-01 in 2018, the methods utilized to measure the fair value of financial instruments at June 30, 2018 represent an approximation of exit price, however, an actual exit price may differ. The following methods, assumptions and valuation techniques were used by First Financial to measure different financial assets and liabilities at fair value on a recurring or nonrecurring basis. Investment securities. Investment securities classified as 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 previously described are considered Level 3. First Financial utilizes values provided by third-party pricing vendors to price the investment securities portfolio in accordance with the fair value hierarchy of the Fair Value Topic and reviews the pricing methodologies utilized by the pricing vendors to ensure that the fair value determination is consistent with the applicable accounting guidance. First Financial’s pricing process includes a series of quality assurance activities where prices are compared to recent market conditions, historical prices and other independent pricing services. Further, the Company periodically validates the fair value of a sample of securities in the portfolio by comparing the fair values to prices from other independent sources for the same or similar securities. First Financial analyzes unusual or significant variances, conducts additional research with the pricing vendor, and if necessary, takes appropriate action based on its findings. The results of the quality assurance process are incorporated into the selection of pricing providers by the portfolio manager. Impaired loans. The fair value of 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 on an outside appraisal, if deemed significant, or the net book value on the applicable borrower financial statements. Likewise, values for inventory and accounts receivable collateral are based on borrower financial statement balances or aging reports on a discounted basis as appropriate (Level 3). 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. Derivatives. The fair values of derivative instruments are based primarily on a net present value calculation of the cash flows related to the interest rate swaps at the reporting date, using primarily observable market inputs such as interest rate yield curves which represents the cost to terminate the swap if First Financial should choose to do so. Additionally, First Financial utilizes an internally-developed model to value the credit risk component of derivative assets and liabilities, which is recorded as an adjustment to the fair value of the derivative asset or liability on the reporting date. Derivative instruments are classified as Level 2 in the fair value hierarchy. The financial assets and liabilities measured at fair value on a recurring basis in the consolidated financial statements were as follows: Fair value measurements using (Dollars in thousands) Level 1 Level 2 Level 3 Assets/liabilities at fair value June 30, 2018 Assets Derivatives $ 0 $ 28,113 $ 0 $ 28,113 Investment securities available-for-sale 7,737 2,647,172 0 2,654,909 Total $ 7,737 $ 2,675,285 $ 0 $ 2,683,022 Liabilities Derivatives $ 0 $ 27,624 $ 0 $ 27,624 Fair value measurements using (Dollars in thousands) Level 1 Level 2 Level 3 Assets/liabilities 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 Certain financial assets and liabilities are measured at fair value on a nonrecurring basis. Adjustments to the fair market value of these assets usually result from the application of fair value accounting or 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 June 30, 2018 Assets Impaired loans $ 0 $ 0 $ 531 OREO 0 0 284 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

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS On April 1, 2018, the Company completed its acquisition of MainSource Financial Group, Inc. and its banking subsidiary, MainSource Bank. Therefore, results of MSFG have been included in the results of operations beginning on April 1, 2018. Under the terms of the merger agreement, shareholders of MSFG received 1.3875 common shares of First Financial common stock for each share of MSFG common stock, with cash paid in lieu of fractional shares. Including outstanding options and warrants to purchase MSFG common stock, the total purchase consideration was $1.1 billion and resulted in goodwill of $678.9 million . The goodwill arising from the acquisition largely reflected synergies and cost savings resulting from combining the operations of the companies. First Financial incurred $25.9 million of merger related expenses related to the acquisition of MSFG during the six months ended June 30, 2018. The acquisition is expected to provide additional revenue growth and diversification. The goodwill is not deductible for income tax purposes as the transaction was accounted for as a tax-free exchange. For further detail, see Note 6 – Goodwill and Other Intangible Assets. The MainSource transaction was accounted for using the acquisition method of accounting and accordingly, assets acquired, liabilities assumed and consideration exchanged were recorded at estimated fair value on the acquisition date, in accordance with FASB ASC Topic 805, Business Combinations. The fair value measurements of assets acquired and liabilities assumed are subject to refinement for up to one year after the closing date of the acquisition as additional information relative to closing date fair values become available. The Company continues to finalize the fair values of loans, intangible assets and liabilities. As a result, the fair value adjustments are preliminary and may change as information becomes available. Fair value adjustments will be finalized no later than April 2019. The following table provides the purchase price calculation as of the acquisition date, identifiable assets purchased and liabilities assumed at their estimated fair value. As a condition of the merger, acquired assets and liabilities held for sale were divested subsequent to the closing of the merger. There was no gain or loss recorded in the Consolidated Statement of Income in conjunction with the divestiture. (Dollars in thousands) MainSource Purchase consideration Cash consideration $ 43 Stock consideration 1,045,876 Warrant consideration 14,460 Options consideration 1,577 Total purchase consideration 1,061,956 Assets acquired Cash 71,681 Investment securities available-for-sale 901,008 Investment securities held-to-maturity 171,423 Other investments 28,763 Loans 2,791,954 Premises and equipment 99,098 Other real estate owned 1,361 Intangible assets 41,750 Other assets 155,945 Assets held for sale 127,775 Total assets acquired 4,390,758 Liabilities assumed Deposits 3,264,038 Subordinated notes 49,027 FHLB advances 291,887 Other borrowings 205,620 Other liabilities 21,449 Liabilities held for sale 175,722 Total liabilities assumed 4,007,743 Net identifiable assets 383,015 Goodwill $ 678,941 The following table presents supplemental pro forma information as if the acquisition had occurred at the beginning of 2017. The pro forma information includes adjustments for interest income on acquired loans, amortization of intangible assets arising from the transaction, depreciation expense on property acquired, interest expense on deposits acquired, merger-related expenses incurred and the related income tax effects. The pro forma financial information is not necessarily indicative of the results of operations that would have occurred had the transactions been effected on the assumed date. The disclosures regarding the results of operations for MSFG subsequent to its acquisition date are omitted as this information is not practical to obtain. The Company converted MSFG's core system in the second quarter of 2018, which is the same quarter as its acquisition date. Six months ended June 30, (Dollars in thousands, except per share data) 2018 2017 Pro Forma Condensed Combined Income Statement Information Net interest income $ 242,130 $ 219,984 Net income $ 106,556 $ 58,755 Basic earnings per share $ 1.09 $ 0.61 Diluted earnings per share $ 1.08 $ 0.60

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2018
Off-Balance-Sheet Credit Exposure, Policy [Policy Text Block]	Letters of credit are conditional commitments issued by First Financial to guarantee the performance of a client to a third party.  First Financial’s portfolio of 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.
Basis of Presentation Policy	The Consolidated Financial Statements of First Financial Bancorp., a financial holding company principally serving Ohio, Indiana, Kentucky and Illinois, include the accounts and operations of First Financial and its wholly-owned subsidiary, First Financial Bank. All significant intercompany transactions and accounts have been eliminated in consolidation.  Certain reclassifications of prior periods' amounts have been made to conform to current year presentation. Such reclassifications had no effect on net earnings.
Use of Estimates, Policy	The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes. These estimates, assumptions and judgments are inherently subjective and may be susceptible to significant change. Actual realized amounts could differ materially from these estimates.
Loans and Leases Receivable, Past Due Status, Policy	Loans are considered past due or delinquent when the contractual principal or interest due in accordance with the terms of the loan agreement or any portion thereof remains unpaid after the date of the scheduled payment.
Loans and Leases Receivable, Nonaccrual Loan and Lease Status, Policy	Loans are classified as nonaccrual when, in the opinion of management, collection of principal or interest is doubtful or when principal or interest payments are 90 days or more past due. Generally, loans are classified as nonaccrual due to the continued failure to adhere to contractual payment terms by the borrower, coupled with other pertinent factors. When a loan is classified as nonaccrual, the accrual of interest income is discontinued and previously accrued but unpaid interest is reversed. Any payments received while a loan is on nonaccrual status are applied as a reduction to the carrying value of the loan. A loan classified as nonaccrual may return to accrual status if 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.
Loans and Leases Receivable, Troubled Debt Restructuring Policy	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.
Impaired Financing Receivable, Policy	First Financial individually reviews all impaired commercial loan relationships, as well as consumer loan TDRs, greater than $250,000
Loans and Leases Receivable, Real Estate Acquired Through Foreclosure, Policy	OREO consists of properties acquired by the Company primarily through the loan foreclosure or repossession process, or other resolution activity that results in partial or total satisfaction of problem loans.
Loans and Leases Receivable, Allowance for Loan Losses Policy	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.
Goodwill and Intangible Assets, Goodwill, Policy	Assets and liabilities acquired in a business combination are recorded at their estimated fair values as of the acquisition date. The excess cost of the acquisition over the fair value of net assets acquired is recorded as goodwill.
Goodwill and Intangible Assets, Goodwill Impairment Policy	Goodwill is evaluated for impairment on an annual basis as of October 1 of each year, or whenever events or changes in circumstances indicate that the fair value of a reporting unit may be below its carrying value.
Goodwill and Intangible Assets, Policy	Core deposit intangibles represent the estimated fair value of acquired customer deposit relationships on the date of acquisition and are amortized on an accelerated basis
Income Tax, Policy	The unrecognized tax benefits relate to state income tax exposures from taking tax positions where the Company believes it is likely that, upon examination, a state may take a position contrary to the position taken by First Financial.
Commitments and Contingencies, Policy	First Financial offers a variety of financial instruments including standby letters of credit and outstanding commitments to extend credit to assist clients in meeting their requirement for liquidity and credit enhancement. GAAP does not require these financial instruments to be recorded in the Consolidated Financial Statements.
Fair Value Measurement, Policy [Policy Text Block]	The fair value framework as disclosed in the Fair Value Topic includes a hierarchy which focuses on prioritizing the inputs used in valuation techniques. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1), a lower priority to observable inputs other than quoted prices in active markets for identical assets and liabilities (Level 2) and the lowest priority to unobservable inputs (Level 3). When determining the fair value measurements for assets and liabilities, First Financial looks to active markets to price identical assets or liabilities whenever possible and classifies such items in Level 1. When identical assets and liabilities are not traded in active markets, First Financial looks to observable market data for similar assets and liabilities and classifies such items as Level 2. Certain assets and liabilities are not actively traded in observable markets and First Financial must use alternative techniques, based on unobservable inputs, to determine the fair value and classifies such items as Level 3. The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement.
Fair Value of Financial Instruments, Policy	The following methods, assumptions and valuation techniques were used by First Financial to measure different financial assets and liabilities at fair value on a recurring or nonrecurring basis. Investment securities. Investment securities classified as 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 previously described are considered Level 3. First Financial utilizes values provided by third-party pricing vendors to price the investment securities portfolio in accordance with the fair value hierarchy of the Fair Value Topic and reviews the pricing methodologies utilized by the pricing vendors to ensure that the fair value determination is consistent with the applicable accounting guidance. First Financial’s pricing process includes a series of quality assurance activities where prices are compared to recent market conditions, historical prices and other independent pricing services. Further, the Company periodically validates the fair value of a sample of securities in the portfolio by comparing the fair values to prices from other independent sources for the same or similar securities. First Financial analyzes unusual or significant variances, conducts additional research with the pricing vendor, and if necessary, takes appropriate action based on its findings. The results of the quality assurance process are incorporated into the selection of pricing providers by the portfolio manager. Impaired loans. The fair value of 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 on an outside appraisal, if deemed significant, or the net book value on the applicable borrower financial statements. Likewise, values for inventory and accounts receivable collateral are based on borrower financial statement balances or aging reports on a discounted basis as appropriate (Level 3). 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. Derivatives.
Loan Commitments, Policy [Policy Text Block]	Loan commitments are agreements to extend credit to a client, absent any violation of conditions established in the commitment agreement.  Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee.  Since many of the commitments 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.
Other Contract-Mortgage
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial enters into IRLCs and forward commitments for the future delivery of mortgage loans to third party investors, which are considered derivatives. When borrowers secure 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 loans held for sale.
Credit Risk
Derivatives, Methods of Accounting, Hedging Derivatives, Policy	First Financial manages 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, Policy	First Financial utilizes interest rate swaps as a means to offer commercial borrowers fixed rate funding while providing the Company with floating rate assets.

INVESTMENTS (Tables)

INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, 2018 : Held-to-maturity Available-for-sale (Dollars in thousands) Amortized Unrecognized gain Unrecognized loss Fair Amortized cost Unrealized gain Unrealized loss Fair U.S. Treasuries $ 0 $ 0 $ 0 $ 0 $ 98 $ 0 $ (3 ) $ 95 Securities of U.S. government agencies and corporations 0 0 0 0 34,896 84 (452 ) 34,528 Mortgage-backed securities - residential 31,857 0 (1,515 ) 30,342 644,358 1,314 (10,152 ) 635,520 Mortgage-backed securities - commercial 152,906 13 (5,503 ) 147,416 290,930 106 (5,059 ) 285,977 Collateralized mortgage obligations 13,982 0 (675 ) 13,307 873,923 965 (10,313 ) 864,575 Obligations of state and other political subdivisions 245,212 936 (1,428 ) 244,720 250,993 2,214 (1,910 ) 251,297 Asset-backed securities 0 0 0 0 492,702 879 (1,354 ) 492,227 Other securities 0 0 0 0 89,357 1,938 (605 ) 90,690 Total $ 443,957 $ 949 $ (9,121 ) $ 435,785 $ 2,677,257 $ 7,500 $ (29,848 ) $ 2,654,909 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 Unrecognized gain 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 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
Summary of Investment Securities by Estimated Maturity	The following table provides a summary of investment securities by contractual maturity as of June 30, 2018 , 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 By Contractual Maturity: Due in one year or less $ 0 $ 0 $ 4,125 $ 4,123 Due after one year through five years 275 279 70,801 70,802 Due after five years through ten years 15,799 15,778 140,577 142,222 Due after ten years 229,138 228,663 159,841 159,463 Mortgage-backed securities - residential 31,857 30,342 644,358 635,520 Mortgage-backed securities - commercial 152,906 147,416 290,930 285,977 Collateralized mortgage obligations 13,982 13,307 873,923 864,575 Asset-backed securities 0 0 492,702 492,227 Total $ 443,957 $ 435,785 $ 2,677,257 $ 2,654,909
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: June 30, 2018 Less than 12 months 12 months or more Total (Dollars in thousands) Fair value Unrealized loss Fair Unrealized Fair Unrealized U.S. Treasuries $ 95 $ (3 ) $ 0 $ 0 $ 95 $ (3 ) Securities of U.S. Government agencies and corporations 19,890 (311 ) 5,379 (141 ) 25,269 (452 ) Mortgage-backed securities - residential 488,725 (5,650 ) 129,218 (6,017 ) 617,943 (11,667 ) Mortgage-backed securities - commercial 278,366 (5,414 ) 88,624 (5,148 ) 366,990 (10,562 ) Collateralized mortgage obligations 628,667 (6,910 ) 99,142 (4,078 ) 727,809 (10,988 ) Obligations of state and other political subdivisions 186,269 (2,195 ) 27,441 (1,143 ) 213,710 (3,338 ) Asset-backed securities 219,064 (1,215 ) 13,591 (139 ) 232,655 (1,354 ) Other securities 17,299 (226 ) 7,571 (379 ) 24,870 (605 ) Total $ 1,838,375 $ (21,924 ) $ 370,966 $ (17,045 ) $ 2,209,341 $ (38,969 ) December 31, 2017 Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair Unrealized (Dollars in thousands) value loss value loss value 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 )

LOANS AND LEASES (Tables)

LOANS AND LEASES (Tables)	6 Months Ended
	Jun. 30, 2018
Receivables [Abstract]
Commercial and Consumer Credit Exposure by Risk Attribute	Commercial and consumer credit exposure by risk attribute was as follows: As of June 30, 2018 Commercial Real Estate Lease (Dollars in thousands) & industrial Construction Commercial financing Total Pass $ 2,367,649 $ 543,479 $ 3,794,902 $ 94,763 $ 6,800,793 Special Mention 24,261 11,947 29,399 0 65,607 Substandard 48,686 42 64,692 1,435 114,855 Doubtful 0 0 0 0 0 Total $ 2,440,596 $ 555,468 $ 3,888,993 $ 96,198 $ 6,981,255 (Dollars in thousands) Residential real estate Home equity Installment Credit card Total Performing $ 905,649 $ 828,558 $ 100,422 $ 48,665 $ 1,883,294 Nonperforming 13,255 6,473 304 0 20,032 Total $ 918,904 $ 835,031 $ 100,726 $ 48,665 $ 1,903,326 As of December 31, 2017 Commercial Real Estate Lease (Dollars in thousands) & industrial Construction Commercial 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 (Dollars in thousands) 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
Loan Delinquency, including Nonaccrual Loans	Loan delinquency, including loans classified as nonaccrual, was as follows: As of June 30, 2018 (Dollars in thousands) 30 – 59 60 – 89 > 90 days Total Current Subtotal Purchased impaired Total > 90 days Loans Commercial & industrial $ 1,885 $ 389 $ 2,814 $ 5,088 $ 2,429,204 $ 2,434,292 $ 6,304 $ 2,440,596 $ 0 Lease financing 0 0 0 0 96,198 96,198 0 96,198 0 Construction real estate 447 0 0 447 554,754 555,201 267 555,468 0 Commercial real estate 3,291 1,829 15,999 21,119 3,803,534 3,824,653 64,340 3,888,993 16 Residential real estate 1,962 601 2,945 5,508 872,404 877,912 40,992 918,904 0 Home equity 3,834 750 3,443 8,027 822,359 830,386 4,645 835,031 0 Installment 165 22 263 450 99,669 100,119 607 100,726 0 Credit card 427 216 311 954 47,711 48,665 0 48,665 311 Total $ 12,011 $ 3,807 $ 25,775 $ 41,593 $ 8,725,833 $ 8,767,426 $ 117,155 $ 8,884,581 $ 327 As of December 31, 2017 (Dollars in thousands) 30 – 59 60 – 89 > 90 days Total Current Subtotal Purchased impaired Total > 90 days Loans Commercial & 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
Loans Restructured During Period	The following tables provide information on loan modifications classified as TDRs during the three and six months ended June 30, 2018 and 2017 : Three months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial & industrial 8 $ 6,221 $ 6,183 4 $ 2,177 $ 2,183 Construction real estate 0 0 0 0 0 0 Commercial real estate 4 2,047 2,016 6 1,506 1,449 Residential real estate 1 201 201 0 0 0 Home equity 0 0 0 0 0 0 Installment 0 0 0 0 0 0 Total 13 $ 8,469 $ 8,400 10 $ 3,683 $ 3,632 Six months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Number of loans Pre-modification loan balance Period end balance Number of loans Pre-modification loan balance Period end balance Commercial & industrial 12 $ 7,149 $ 7,096 6 $ 5,679 $ 5,624 Construction real estate 0 0 0 0 0 0 Commercial real estate 6 2,119 2,088 6 1,506 1,449 Residential real estate 3 294 294 0 0 0 Home equity 0 0 0 0 0 0 Installment 0 0 0 0 0 0 Total 21 $ 9,562 $ 9,478 12 $ 7,185 $ 7,073
Loans Restructured, Modifications	The following table provides information on how TDRs were modified during the three and six months ended June 30, 2018 and 2017 : Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Extended maturities $ 2,000 $ 2,587 $ 2,888 $ 3,261 Adjusted interest rates 0 0 52 2,767 Combination of rate and maturity changes 0 180 0 180 Forbearance 6,199 827 6,199 827 Other (1) 201 38 339 38 Total $ 8,400 $ 3,632 $ 9,478 $ 7,073 (1) Includes covenant modifications and other concessions, or combination of concessions, that do not consist of interest rate adjustments, forbearance and maturity extensions
Nonaccrual, Restructured and Impaired Loans	The following table provides information on impaired loans, excluding purchased impaired loans: (Dollars in thousands) June 30, 2018 December 31, 2017 Impaired loans Nonaccrual loans (1) Commercial & industrial $ 3,448 $ 5,229 Lease financing 0 82 Construction real estate 24 29 Commercial real estate 21,593 10,616 Residential real estate 9,278 4,140 Home equity 5,820 3,743 Installment 299 243 Nonaccrual loans 40,462 24,082 Accruing troubled debt restructurings 21,839 17,545 Total impaired loans $ 62,301 $ 41,627 (1) Nonaccrual loans include nonaccrual TDRs of $5.9 million and $6.4 million as of June 30, 2018 and December 31, 2017 , respectively. Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Interest income effect on impaired loans Gross amount of interest that would have been recorded under original terms $ 1,132 $ 1,158 $ 1,934 $ 1,974 Interest included in income Nonaccrual loans 146 163 226 305 Troubled debt restructurings 189 169 313 395 Total interest included in income 335 332 539 700 Net impact on interest income $ 797 $ 826 $ 1,395 $ 1,274
Investment in Impaired Loans	First Financial's investment in impaired loans was as follows: As of June 30, 2018 As of December 31, 2017 (Dollars in thousands) Current balance Contractual principal balance Related allowance Current balance Contractual Related Loans with no related allowance recorded Commercial & industrial $ 10,856 $ 14,647 $ 0 $ 7,162 $ 8,460 $ 0 Lease financing 0 0 0 82 82 0 Construction real estate 24 57 0 29 60 0 Commercial real estate 30,655 36,421 0 18,423 20,837 0 Residential real estate 12,216 14,383 0 6,876 8,145 0 Home equity 6,372 7,311 0 4,356 5,399 0 Installment 304 603 0 255 422 0 Total 60,427 73,422 0 37,183 43,405 0 Loans with an allowance recorded Commercial & industrial 379 379 179 169 169 169 Lease financing 0 0 0 0 0 0 Construction real estate 0 0 0 0 0 0 Commercial real estate 356 356 25 3,119 3,120 448 Residential real estate 1,039 1,039 160 1,056 1,063 160 Home equity 100 100 2 100 100 2 Installment 0 0 0 0 0 0 Total 1,874 1,874 366 4,444 4,452 779 Total Commercial & industrial 11,235 15,026 179 7,331 8,629 169 Lease financing 0 0 0 82 82 0 Construction real estate 24 57 0 29 60 0 Commercial real estate 31,011 36,777 25 21,542 23,957 448 Residential real estate 13,255 15,422 160 7,932 9,208 160 Home equity 6,472 7,411 2 4,456 5,499 2 Installment 304 603 0 255 422 0 Total $ 62,301 $ 75,296 $ 366 $ 41,627 $ 47,857 $ 779 First Financial's average impaired loans by class and interest income recognized by class was as follows: Three months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Average Interest Average Interest Loans with no related allowance recorded Commercial & industrial $ 9,714 $ 73 $ 17,198 $ 87 Lease financing 0 0 98 1 Construction real estate 25 1 1,075 0 Commercial real estate 27,516 140 25,465 144 Residential real estate 9,173 76 7,605 46 Home equity 5,222 27 3,926 27 Installment 305 1 357 1 Total 51,955 318 55,724 306 Loans with an allowance recorded Commercial & industrial 309 6 2,301 11 Lease financing 0 0 0 0 Construction real estate 0 0 0 0 Commercial real estate 358 3 658 8 Residential real estate 1,042 7 1,126 6 Home equity 101 1 101 1 Installment 0 0 0 0 Total 1,810 17 4,186 26 Total Commercial & industrial 10,023 79 19,499 98 Lease financing 0 0 98 1 Construction real estate 25 1 1,075 0 Commercial real estate 27,874 143 26,123 152 Residential real estate 10,215 83 8,731 52 Home equity 5,323 28 4,027 28 Installment 305 1 357 1 Total $ 53,765 $ 335 $ 59,910 $ 332 Six months ended June 30, 2018 June 30, 2017 (Dollars in thousands) Average Interest Average Interest Loans with no related allowance recorded Commercial & industrial $ 8,863 $ 99 $ 15,607 $ 196 Lease financing 27 0 149 2 Construction real estate 26 2 538 0 Commercial real estate 24,485 239 19,939 304 Residential real estate 8,407 123 8,032 92 Home equity 4,933 47 4,111 51 Installment 288 1 413 3 Total 47,029 511 48,789 648 Loans with an allowance recorded Commercial & industrial 262 6 1,094 24 Lease financing 0 0 0 0 Construction real estate 0 0 0 0 Commercial real estate 1,278 6 4,374 13 Residential real estate 1,047 14 1,185 13 Home equity 100 2 101 2 Installment 0 0 0 0 Total 2,687 28 6,754 52 Total Commercial & industrial 9,125 105 16,701 220 Lease financing 27 0 149 2 Construction real estate 26 2 538 0 Commercial real estate 25,763 245 24,313 317 Residential real estate 9,454 137 9,217 105 Home equity 5,033 49 4,212 53 Installment 288 1 413 3 Total $ 49,716 $ 539 $ 55,543 $ 700
Changes in Other Real Estate Owned	Changes in OREO were as follows: Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Balance at beginning of period $ 1,065 $ 5,300 $ 2,781 $ 6,284 Additions Commercial & industrial 1,020 50 1,190 172 Residential real estate 525 1,913 984 2,078 Total additions 1,545 1,963 2,174 2,250 Disposals Commercial & industrial (326 ) (682 ) (2,430 ) (1,607 ) Residential real estate (292 ) (448 ) (410 ) (685 ) Total disposals (618 ) (1,130 ) (2,840 ) (2,292 ) Valuation adjustment Commercial & industrial 0 (116 ) (97 ) (162 ) Residential real estate (139 ) (56 ) (165 ) (119 ) Total valuation adjustment (139 ) (172 ) (262 ) (281 ) Balance at end of period $ 1,853 $ 5,961 $ 1,853 $ 5,961

ALLOWANCE FOR LOAN AND LEASE 28

ALLOWANCE FOR LOAN AND LEASE LOSSES (Tables)	6 Months Ended
	Jun. 30, 2018
Receivables [Abstract]
Allowance for Loan and Lease Losses by Classification	Changes in the ALLL by loan category were as follows: Three months ended June 30, 2018 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 period $ 18,038 $ 626 $ 4,267 $ 20,321 $ 4,727 $ 4,828 $ 290 $ 1,283 $ 54,380 Provision for loan and lease losses 3,328 170 (282 ) (619 ) (28 ) 171 136 859 3,735 Gross charge-offs (4,356 ) 0 0 (78 ) (101 ) (385 ) (218 ) (684 ) (5,822 ) Recoveries 518 1 0 887 70 187 82 38 1,783 Total net charge-offs (3,838 ) 1 0 809 (31 ) (198 ) (136 ) (646 ) (4,039 ) Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 Three months ended June 30, 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 period $ 17,148 $ 616 $ 3,607 $ 23,745 $ 5,485 $ 3,774 $ 419 $ 1,532 $ 56,326 Provision for loan and lease losses 3,537 (67 ) (280 ) (2,941 ) (305 ) 526 19 (22 ) 467 Loans charged off (3,065 ) 0 0 (485 ) (223 ) (384 ) (126 ) (215 ) (4,498 ) Recoveries 693 1 89 1,398 59 222 43 73 2,578 Total net charge-offs (2,372 ) 1 89 913 (164 ) (162 ) (83 ) (142 ) (1,920 ) Ending allowance for loan and lease losses $ 18,313 $ 550 $ 3,416 $ 21,717 $ 5,016 $ 4,138 $ 355 $ 1,368 $ 54,873 Six months ended June 30, 2018 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Allowance for loan and lease losses: Balance at beginning of period $ 17,598 $ 675 $ 3,577 $ 20,930 $ 4,683 $ 4,935 $ 307 $ 1,316 $ 54,021 Provision for loan and lease losses 4,217 121 408 196 86 (123 ) 87 1,046 6,038 Loans charged off (5,241 ) 0 0 (2,254 ) (197 ) (627 ) (234 ) (938 ) (9,491 ) Recoveries 954 1 0 1,639 96 616 130 72 3,508 Total net charge-offs (4,287 ) 1 0 (615 ) (101 ) (11 ) (104 ) (866 ) (5,983 ) Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 As of June 30, 2018 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance balance attributable to loans Individually evaluated for impairment $ 179 $ 0 $ 0 $ 25 $ 160 $ 2 $ 0 $ 0 $ 366 Collectively evaluated for impairment 17,349 797 3,985 20,486 4,508 4,799 290 1,496 53,710 Ending allowance for loan and lease losses $ 17,528 $ 797 $ 3,985 $ 20,511 $ 4,668 $ 4,801 $ 290 $ 1,496 $ 54,076 Loans Individually evaluated for impairment $ 11,235 $ 0 $ 24 $ 31,011 $ 13,255 $ 6,472 $ 304 $ 0 $ 62,301 Collectively evaluated for impairment 2,429,361 96,198 555,444 3,857,982 905,649 828,559 100,422 48,665 8,822,280 Total loans $ 2,440,596 $ 96,198 $ 555,468 $ 3,888,993 $ 918,904 $ 835,031 $ 100,726 $ 48,665 $ 8,884,581 Six months ended June 30, 2017 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Allowance for loan and lease losses: Balance at beginning of period $ 19,225 $ 716 $ 3,282 $ 26,540 $ 3,208 $ 3,043 $ 388 $ 1,559 $ 57,961 Provision for loan and lease losses 2,941 (167 ) 45 (5,507 ) 2,024 1,331 28 139 834 Loans charged off (4,808 ) 0 0 (970 ) (284 ) (564 ) (175 ) (447 ) (7,248 ) Recoveries 955 1 89 1,654 68 328 114 117 3,326 Total net charge-offs (3,853 ) 1 89 684 (216 ) (236 ) (61 ) (330 ) (3,922 ) Ending allowance for loan and lease losses $ 18,313 $ 550 $ 3,416 $ 21,717 $ 5,016 $ 4,138 $ 355 $ 1,368 $ 54,873 As of December 31, 2017 Real Estate (Dollars in thousands) Commercial & industrial Lease financing Construction Commercial Residential Home equity Installment Credit card Total Ending allowance balance attributable to loans Individually evaluated for impairment $ 169 $ 0 $ 0 $ 448 $ 160 $ 2 $ 0 $ 0 $ 779 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 Individually evaluated for impairment $ 7,331 $ 82 $ 29 $ 21,542 $ 7,932 $ 4,456 $ 255 $ 0 $ 41,627 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

GOODWILL (Tables)

GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	(Dollars in thousands) June 30, December 31, Balance at beginning of year $ 204,084 $ 204,084 Goodwill resulting from business combinations 678,941 0 Balance at end of period $ 883,025 $ 204,084

BORROWINGS (Tables)

BORROWINGS (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Summary of Long-term Debt	The following is a summary of First Financial's long-term debt: June 30, 2018 December 31, 2017 (Dollars in thousands) Amount Average rate Amount Average rate Subordinated notes $ 177,887 5.13 % $ 120,000 5.13 % Unamortized discount and debt issuance costs (8,819 ) N/A (1,362 ) N/A FHLB borrowings 299,580 1.90 % 241 1.09 % Capital loan with municipality 775 0.00 % 775 0.00 % Total long-term debt $ 469,423 3.16 % $ 119,654 5.14 %

ACCUMULATED OTHER COMPREHENSI31

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Related Tax Effects Allocated to Other Comprehensive Income and Accumulated Other Comprehensive Income (Loss)	The related tax effects allocated to other comprehensive incom e and reclassifications out of accumulated other comprehensive income (loss) are as follows: Three months ended June 30, 2018 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Reclass from Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ (11,456 ) $ (30 ) $ (11,426 ) $ 2,448 $ (8,978 ) $ (10,051 ) $ (8,978 ) $ (19,029 ) Unrealized gain (loss) on derivatives 203 0 203 (44 ) 159 (545 ) 159 (386 ) Retirement obligation 0 (452 ) 452 42 494 (24,087 ) 494 (23,593 ) Total $ (11,253 ) $ (482 ) $ (10,771 ) $ 2,446 $ (8,325 ) $ (34,683 ) $ (8,325 ) $ (43,008 ) Three months ended June 30, 2017 Total other comprehensive income (loss) Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Reclass from Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 7,170 $ 838 $ 6,332 $ (2,256 ) $ 4,076 $ (3,062 ) $ 4,076 $ 1,014 Unrealized gain (loss) on derivatives 202 0 202 (74 ) 128 (963 ) 128 (835 ) Retirement obligation 0 (335 ) 335 (122 ) 213 (22,614 ) 213 (22,401 ) Total $ 7,372 $ 503 $ 6,869 $ (2,452 ) $ 4,417 $ (26,639 ) $ 4,417 $ (22,222 ) Six months ended June 30, 2018 Total other comprehensive income Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Pre-tax Tax effect Net of tax Beginning Balance Net Activity Reclass of Stranded Tax Effects Ending Balance Unrealized gain (loss) on investment securities $ (23,992 ) $ (30 ) $ (23,962 ) $ 5,154 $ (18,808 ) $ (182 ) $ (18,808 ) $ (39 ) $ (19,029 ) Unrealized gain (loss) on derivatives 405 0 405 (90 ) 315 (577 ) 315 (124 ) (386 ) Retirement obligation 0 (871 ) 871 (54 ) 817 (19,631 ) 817 (4,779 ) (23,593 ) Total $ (23,587 ) $ (901 ) $ (22,686 ) $ 5,010 $ (17,676 ) $ (20,390 ) $ (17,676 ) $ (4,942 ) $ (43,008 ) Six months ended June 30, 2017 Total other comprehensive income Total accumulated other comprehensive income (loss) (Dollars in thousands) Prior to Reclass Pre-tax Tax effect Net of tax Beginning Balance Net Activity Ending Balance Unrealized gain (loss) on investment securities $ 10,002 $ 1,354 $ 8,648 $ (3,085 ) $ 5,563 $ (4,549 ) $ 5,563 $ 1,014 Unrealized gain (loss) on derivatives 405 0 405 (149 ) 256 (1,091 ) 256 (835 ) Retirement obligation 0 (670 ) 670 (268 ) 402 (22,803 ) 402 (22,401 ) Total $ 10,407 $ 684 $ 9,723 $ (3,502 ) $ 6,221 $ (28,443 ) $ 6,221 $ (22,222 )
Other Accumulated Comprehensive income reclassified from AOCI	The following table presents the activity reclassified from accumulated other comprehensive income into income during the three and six month periods ended June 30, 2018 and 2017, respectively: Amount reclassified from accumulated other comprehensive income (1) Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Affected Line Item in the Consolidated Statements of Income Realized gain (loss) on securities available-for-sale $ (30 ) $ 838 $ (30 ) $ 1,354 Net gain (loss) on sales of investments securities Defined benefit pension plan Amortization of prior service cost (2) 103 104 206 207 Other noninterest expense (2018) Salaries and employee benefits (2017) Recognized net actuarial loss (2) (555 ) (439 ) (1,077 ) (877 ) Other noninterest expense (2018) Defined benefit pension plan total (452 ) (335 ) (871 ) (670 ) Total reclassifications for the period, before tax $ (482 ) $ 503 $ (901 ) $ 684 (1) Negative amounts are reductions to net income. (2)

DERIVATIVES (Tables)

DERIVATIVES (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Derivative Financial Instruments and Balances	The following table details the classification and amounts recognized in the Consolidated Balance Sheets for client derivatives: June 30, 2018 December 31, 2017 Estimated fair value Estimated fair value (Dollars in thousands) Balance sheet classification Notional amount Gain Loss Notional amount Gain Loss Client derivatives - instruments associated with loans Matched interest rate swaps with borrower Accrued interest and other assets $ 1,179,156 $ 3,261 $ (24,306 ) $ 837,040 $ 7,153 $ (5,529 ) Matched interest rate swaps with counterparty Accrued interest and other liabilities 1,179,156 24,306 (3,259 ) 837,040 5,529 (7,158 ) Total $ 2,358,312 $ 27,567 $ (27,565 ) $ 1,674,080 $ 12,682 $ (12,687 )
Disclosure by Type of Financial Instrument	The following table discloses the gross and net amounts of client derivative liabilities recognized in the Consolidated Balance Sheets: June 30, 2018 December 31, 2017 (Dollars in thousands) Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of liabilities presented in the Consolidated Balance Sheets Gross amounts of recognized liabilities Gross amounts offset in the Consolidated Balance Sheets Net amounts of liabilities presented in the Consolidated Balance Sheets Client derivatives Matched interest rate swaps with counterparty $ 27,567 $ (7,152 ) $ 20,415 $ 12,687 $ 2,279 $ 14,966
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 June 30, 2018 : 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 $ 1,179,156 4.8 $ (21,045 ) 4.50 % 4.25 % Pay fixed, matched interest rate swaps with counterparty 1,179,156 4.8 21,047 4.25 % 4.50 % Total client derivatives $ 2,358,312 4.8 $ 2 4.37 % 4.37 %

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	6 Months Ended
	Jun. 30, 2018
Retirement Benefits [Abstract]
Employee Benefit Plan Amounts Recognized in the Consolidated Balance Sheets and Consolidated Statements of Income	The following table sets forth information concerning amounts recognized in First Financial’s Consolidated Statements of Income related to the Company's pension plan: Three months ended Six months ended June 30, June 30, (Dollars in thousands) 2018 2017 2018 2017 Service cost $ 1,735 $ 1,239 $ 3,030 $ 2,477 Interest cost 601 589 1,191 1,178 Expected return on assets (2,450 ) (2,481 ) (4,910 ) (4,962 ) Amortization of prior service cost (103 ) (104 ) (206 ) (207 ) Net actuarial loss 555 439 1,077 877 Net periodic benefit cost (income) $ 338 $ (318 ) $ 182 $ (637 )

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	6 Months Ended
	Jun. 30, 2018
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: Three months ended Six months ended June 30, June 30, (Dollars in thousands, except per share data) 2018 2017 2018 2017 Numerator Net income available to common shareholders $ 36,418 $ 22,736 $ 66,924 $ 47,150 Denominator Basic earnings per common share - weighted average shares 97,347,533 61,543,478 79,599,709 61,471,347 Effect of dilutive securities Employee stock awards 545,374 625,031 504,914 649,706 Warrants 539,165 65,513 524,872 66,420 Diluted earnings per common share - adjusted weighted average shares 98,432,072 62,234,022 80,629,495 62,187,473 Earnings per share available to common shareholders Basic $ 0.37 $ 0.37 $ 0.84 $ 0.77 Diluted $ 0.37 $ 0.37 $ 0.83 $ 0.76

FAIR VALUE DISCLOSURES (Tables)

FAIR VALUE DISCLOSURES (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
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 June 30, 2018 Financial assets Cash and short-term investments $ 254,582 $ 254,582 $ 254,582 $ 0 $ 0 Investment securities held-to-maturity 443,957 435,785 0 435,785 0 Other investments 95,004 N/A N/A N/A N/A Loans held for sale 15,821 15,821 0 15,821 0 Loans and leases 8,830,505 8,847,519 0 0 8,847,519 Accrued interest receivable 40,152 40,152 0 13,939 26,213 Financial liabilities Deposits 10,103,747 10,073,140 0 10,073,140 0 Short-term borrowings 1,188,303 1,188,303 1,188,303 0 0 Long-term debt 469,423 462,478 0 462,478 0 Accrued interest payable 9,550 9,550 1,577 7,973 0 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 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 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
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The financial assets and liabilities measured at fair value on a recurring basis in the consolidated financial statements were as follows: Fair value measurements using (Dollars in thousands) Level 1 Level 2 Level 3 Assets/liabilities at fair value June 30, 2018 Assets Derivatives $ 0 $ 28,113 $ 0 $ 28,113 Investment securities available-for-sale 7,737 2,647,172 0 2,654,909 Total $ 7,737 $ 2,675,285 $ 0 $ 2,683,022 Liabilities Derivatives $ 0 $ 27,624 $ 0 $ 27,624 Fair value measurements using (Dollars in thousands) Level 1 Level 2 Level 3 Assets/liabilities 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
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 June 30, 2018 Assets Impaired loans $ 0 $ 0 $ 531 OREO 0 0 284 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

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table provides the purchase price calculation as of the acquisition date, identifiable assets purchased and liabilities assumed at their estimated fair value. As a condition of the merger, acquired assets and liabilities held for sale were divested subsequent to the closing of the merger. There was no gain or loss recorded in the Consolidated Statement of Income in conjunction with the divestiture. (Dollars in thousands) MainSource Purchase consideration Cash consideration $ 43 Stock consideration 1,045,876 Warrant consideration 14,460 Options consideration 1,577 Total purchase consideration 1,061,956 Assets acquired Cash 71,681 Investment securities available-for-sale 901,008 Investment securities held-to-maturity 171,423 Other investments 28,763 Loans 2,791,954 Premises and equipment 99,098 Other real estate owned 1,361 Intangible assets 41,750 Other assets 155,945 Assets held for sale 127,775 Total assets acquired 4,390,758 Liabilities assumed Deposits 3,264,038 Subordinated notes 49,027 FHLB advances 291,887 Other borrowings 205,620 Other liabilities 21,449 Liabilities held for sale 175,722 Total liabilities assumed 4,007,743 Net identifiable assets 383,015 Goodwill $ 678,941
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments	Six months ended June 30, (Dollars in thousands, except per share data) 2018 2017 Pro Forma Condensed Combined Income Statement Information Net interest income $ 242,130 $ 219,984 Net income $ 106,556 $ 58,755 Basic earnings per share $ 1.09 $ 0.61 Diluted earnings per share $ 1.08 $ 0.60

RECENTLY ADOPTED AND ISSUED A37

RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Reclassification from AOCI, Current Period, Tax	$ 0
Retained earnings
Reclassification from AOCI, Current Period, Tax	$ 4,942

INVESTMENTS INVESTMENTS - Addit

INVESTMENTS INVESTMENTS - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017
Gain (Loss) on Investments [Line Items]
NumberOfSecuritiesInSecurityPortfolio	1,385		1,385		775
NumberOfSecuritiesInUnrealizedLossPosition	656		656		237
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 216,196	$ 103,400	$ 216,200	$ 125,600
Held-to-maturity Securities, Transferred Security, at Carrying Value	367,900		367,900
Available-for-sale Securities, Gross Realized Gains	3	1,000	3	1,500
Available-for-sale Securities, Gross Realized Losses	$ 33	$ 100	$ 33	$ 100

INVESTMENTS - Summary of Held-T

INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Total	$ 443,957	$ 654,008
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	949	5,572
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(9,121)	(6,479)
Held-to-Maturity Market Value	435,785	653,101
Total	2,677,257	1,348,227
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	7,500	8,328
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(29,848)	(7,147)
Investment securities available-for-sale	2,654,909	1,349,408
U.S. Treasuries
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	98	98
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(3)	(1)
Investment securities available-for-sale	95	97
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	0	11,168
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	(76)
Held-to-Maturity Market Value	0	11,092
Total	34,896	15,695
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	84	220
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(452)	0
Investment securities available-for-sale	34,528	15,915
Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	31,857	162,093
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	2,042
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(1,515)	(1,535)
Held-to-Maturity Market Value	30,342	162,600
Total	644,358	290,793
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,314	849
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(10,152)	(2,599)
Investment securities available-for-sale	635,520	289,043
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	152,906	255,027
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	13	1,372
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(5,503)	(3,000)
Held-to-Maturity Market Value	147,416	253,399
Total	290,930	150,356
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	106	164
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(5,059)	(1,417)
Investment securities available-for-sale	285,977	149,103
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	13,982	143,545
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	354
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(675)	(1,602)
Held-to-Maturity Market Value	13,307	142,297
Total	873,923	306,095
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	965	1,158
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(10,313)	(1,861)
Investment securities available-for-sale	864,575	305,392
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	245,212	82,175
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	936	1,804
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(1,428)	(266)
Held-to-Maturity Market Value	244,720	83,713
Total	250,993	124,269
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,214	2,162
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,910)	(676)
Investment securities available-for-sale	251,297	125,755
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	492,702	377,655
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	879	1,628
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,354)	(306)
Investment securities available-for-sale	492,227	378,977
Other securities
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	89,357	83,266
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,938	2,147
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(605)	(287)
Investment securities available-for-sale	$ 90,690	$ 85,126

INVESTMENTS - Summary of Invest

INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Held-to-Maturity Amortized Cost
Amortized Cost	$ 443,957	$ 654,008
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	435,785	653,101
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	2,677,257	1,348,227
Available-for-Sale Market Value
Investment securities available-for-sale	2,654,909	1,349,408
One Year or Less [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	0
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	0
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	4,125
Available-for-Sale Market Value
Investment securities available-for-sale	4,123
After One Year Through Five Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	275
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	279
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	70,801
Available-for-Sale Market Value
Investment securities available-for-sale	70,802
After Five Years Through Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	15,799
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	15,778
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	140,577
Available-for-Sale Market Value
Investment securities available-for-sale	142,222
After Ten Years [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	229,138
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	228,663
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	159,841
Available-for-Sale Market Value
Investment securities available-for-sale	159,463
Residential Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	31,857	162,093
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	30,342	162,600
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	644,358	290,793
Available-for-Sale Market Value
Investment securities available-for-sale	635,520	289,043
Commercial Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	152,906	255,027
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	147,416	253,399
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	290,930	150,356
Available-for-Sale Market Value
Investment securities available-for-sale	285,977	149,103
Collateralized Mortgage Backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	13,982	143,545
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	13,307	142,297
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	873,923	306,095
Available-for-Sale Market Value
Investment securities available-for-sale	864,575	305,392
Asset-backed Securities [Member]
Held-to-Maturity Amortized Cost
Amortized Cost	0	0
Held-to-Maturity Market Value
Held-to-maturity Securities, Fair Value	0	0
Available-for-Sale Amortized Cost
Available-for-sale Securities, Amortized Cost Basis	492,702	377,655
Available-for-Sale Market Value
Investment securities available-for-sale	$ 492,227	$ 378,977

INVESTMENTS - Age of Gross Unre

INVESTMENTS - Age of Gross Unrealized Losses and Associated Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	$ 1,838,375	$ 570,095
Less than 12 Months Unrealized Loss	(21,924)	(4,745)
12 Months or More Fair Value	370,966	335,516
12 Months or More Unrealized Loss	(17,045)	(8,881)
Total Fair Value	2,209,341	905,611
Total Unrealized Loss	(38,969)	(13,626)
U.S. Treasuries
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	95	97
Less than 12 Months Unrealized Loss	(3)	(1)
12 Months or More Fair Value	0	0
12 Months or More Unrealized Loss	0	0
Total Fair Value	95	97
Total Unrealized Loss	(3)	(1)
Securities of U.S. government agencies and corporations
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	19,890	11,092
Less than 12 Months Unrealized Loss	(311)	(76)
12 Months or More Fair Value	5,379	0
12 Months or More Unrealized Loss	(141)	0
Total Fair Value	25,269	11,092
Total Unrealized Loss	(452)	(76)
Residential Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	488,725	175,183
Less than 12 Months Unrealized Loss	(5,650)	(1,109)
12 Months or More Fair Value	129,218	108,782
12 Months or More Unrealized Loss	(6,017)	(3,025)
Total Fair Value	617,943	283,965
Total Unrealized Loss	(11,667)	(4,134)
Commercial Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	278,366	132,818
Less than 12 Months Unrealized Loss	(5,414)	(1,713)
12 Months or More Fair Value	88,624	72,139
12 Months or More Unrealized Loss	(5,148)	(2,704)
Total Fair Value	366,990	204,957
Total Unrealized Loss	(10,562)	(4,417)
Collateralized Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	628,667	164,909
Less than 12 Months Unrealized Loss	(6,910)	(1,138)
12 Months or More Fair Value	99,142	101,436
12 Months or More Unrealized Loss	(4,078)	(2,325)
Total Fair Value	727,809	266,345
Total Unrealized Loss	(10,988)	(3,463)
Obligations of state and other political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	186,269	38,450
Less than 12 Months Unrealized Loss	(2,195)	(507)
12 Months or More Fair Value	27,441	21,639
12 Months or More Unrealized Loss	(1,143)	(435)
Total Fair Value	213,710	60,089
Total Unrealized Loss	(3,338)	(942)
Asset-backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	219,064	44,941
Less than 12 Months Unrealized Loss	(1,215)	(200)
12 Months or More Fair Value	13,591	24,396
12 Months or More Unrealized Loss	(139)	(106)
Total Fair Value	232,655	69,337
Total Unrealized Loss	(1,354)	(306)
Other securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months Fair Value	17,299	2,605
Less than 12 Months Unrealized Loss	(226)	(1)
12 Months or More Fair Value	7,571	7,124
12 Months or More Unrealized Loss	(379)	(286)
Total Fair Value	24,870	9,729
Total Unrealized Loss	$ (605)	$ (287)

LOANS AND LEASES - Additional I

LOANS AND LEASES - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Apr. 01, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased impaired loans	$ 117,155,000		$ 117,155,000				$ 104,960,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield					$ 1,200,000
Certain Loans Acquired in Transfer, Nonaccretable Difference					2,700,000
Restructured Loans, Nonaccrual Status	5,900,000		5,900,000				6,400,000
Write-downs	139,000	$ 172,000	262,000	$ 281,000
Gain (loss) on sale of other real estate owned	283,000	(162,000)	206,000	(186,000)
Real Estate Acquired Through Foreclosure	1,853,000	5,961,000	1,853,000	5,961,000		$ 1,065,000	$ 2,781,000	$ 5,300,000	$ 6,284,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, at Acquisition, at Fair Value					2,700,000,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition					$ 2,900,000,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum			250,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured Loans, Loan Relationships, Review Threshold Amount Minimum			250,000
Write-downs	139,000	$ 56,000	165,000	$ 119,000
MainSource [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased impaired loans	$ 24,100,000		$ 24,100,000

LOANS AND LEASES - Commercial a

LOANS AND LEASES - Commercial and Consumer Credit Exposure by Risk Attribute (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Commercial	$ 2,440,596	$ 1,912,743
Real Estate - Construction	555,468	467,730
Real Estate - Commercial	3,888,993	2,490,091
Lease financing	96,198	89,347
Total Commercial	6,981,255	4,959,911
Pass
Financing Receivable, Recorded Investment [Line Items]
Commercial	2,367,649	1,882,464
Real Estate - Construction	543,479	467,687
Real Estate - Commercial	3,794,902	2,446,999
Lease financing	94,763	88,078
Total Commercial	6,800,793	4,885,228
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Commercial	24,261	6,226
Real Estate - Construction	11,947	0
Real Estate - Commercial	29,399	4,436
Lease financing	0	0
Total Commercial	65,607	10,662
Substandard
Financing Receivable, Recorded Investment [Line Items]
Commercial	48,686	24,053
Real Estate - Construction	42	43
Real Estate - Commercial	64,692	38,656
Lease financing	1,435	1,269
Total Commercial	114,855	64,021
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Commercial	0	0
Real Estate - Construction	0	0
Real Estate - Commercial	0	0
Lease financing	0	0
Total Commercial	0	0
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	918,904	471,391
Residential real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	905,649	463,459
Residential real estate | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	13,255	7,932
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	835,031	493,604
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	828,558	489,148
Home equity | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	6,473	4,456
Installment
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	100,726	41,586
Installment | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	100,422	41,331
Installment | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	304	255
Credit card
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	48,665	46,691
Credit card | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	48,665	46,691
Credit card | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	0	0
Total consumer loans
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	1,903,326	1,053,272
Total consumer loans | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	1,883,294	1,040,629
Total consumer loans | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 20,032	$ 12,643

LOANS AND LEASES - Loan Delinqu

LOANS AND LEASES - Loan Delinquency, including Nonaccrual Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 41,593	$ 27,942
Current	8,725,833	5,880,281
Loans and Leases Receivable, Gross	8,767,426	5,908,223
Purchased impaired loans	117,155	104,960
Total loans and leases	8,884,581	6,013,183
> 90 days past due and still accruing	327	62
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	12,011	6,896
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,807	3,179
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	25,775	17,867
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	5,088	7,490
Current	2,429,204	1,901,821
Loans and Leases Receivable, Gross	2,434,292	1,909,311
Purchased impaired loans	6,304	3,432
Total loans and leases	2,440,596	1,912,743
> 90 days past due and still accruing	0	0
Commercial | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,885	755
Commercial | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	389	1,657
Commercial | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,814	5,078
Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	485
Current	96,198	88,862
Loans and Leases Receivable, Gross	96,198	89,347
Purchased impaired loans	0	0
Total loans and leases	96,198	89,347
> 90 days past due and still accruing	0	0
Lease financing | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	485
Lease financing | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Lease financing | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	447	234
Current	554,754	467,216
Loans and Leases Receivable, Gross	555,201	467,450
Purchased impaired loans	267	280
Total loans and leases	555,468	467,730
> 90 days past due and still accruing	0	0
Construction real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	447	234
Construction real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	21,119	10,694
Current	3,803,534	2,419,969
Loans and Leases Receivable, Gross	3,824,653	2,430,663
Purchased impaired loans	64,340	59,428
Total loans and leases	3,888,993	2,490,091
> 90 days past due and still accruing	16	0
Commercial real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,291	1,716
Commercial real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,829	201
Commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	15,999	8,777
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	5,508	3,329
Current	872,404	430,500
Loans and Leases Receivable, Gross	877,912	433,829
Purchased impaired loans	40,992	37,562
Total loans and leases	918,904	471,391
> 90 days past due and still accruing	0	0
Residential real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,962	526
Residential real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	601	811
Residential real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,945	1,992
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	8,027	4,863
Current	822,359	485,127
Loans and Leases Receivable, Gross	830,386	489,990
Purchased impaired loans	4,645	3,614
Total loans and leases	835,031	493,604
> 90 days past due and still accruing	0	0
Home equity | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,834	2,716
Home equity | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	750	394
Home equity | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,443	1,753
Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	450	413
Current	99,669	40,529
Loans and Leases Receivable, Gross	100,119	40,942
Purchased impaired loans	607	644
Total loans and leases	100,726	41,586
> 90 days past due and still accruing	0	0
Installment | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	165	179
Installment | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	22	29
Installment | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	263	205
Credit card
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	954	434
Current	47,711	46,257
Loans and Leases Receivable, Gross	48,665	46,691
Purchased impaired loans	0	0
Total loans and leases	48,665	46,691
> 90 days past due and still accruing	311	62
Credit card | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	427	285
Credit card | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	216	87
Credit card | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 311	$ 62

LOANS AND LEASES - Restructured

LOANS AND LEASES - Restructured Loans (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)loans	Jun. 30, 2017USD ($)loans	Jun. 30, 2018USD ($)loansd	Jun. 30, 2017USD ($)loans	Dec. 31, 2017USD ($)loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extended Maturities	$ 2,000,000	$ 2,587,000	$ 2,888,000	$ 3,261,000
Adjusted Interest Rates	0	0	52,000	2,767,000
Combined Rate And Maturity	0	180,000	0	180,000
Forebearance Agreements	6,199,000	827,000	6,199,000	827,000
Other	201,000	38,000	339,000	38,000
Total	$ 8,400,000	$ 3,632,000	$ 9,478,000	$ 7,073,000
Restructured loans, Number of Loans | loans	13	10	21	12
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 8,469,000	$ 3,683,000	$ 9,562,000	$ 7,185,000
Restructured loans, Period End Balance	$ 8,400,000	$ 3,632,000	$ 9,478,000	$ 7,073,000
Restructured loans with payment default within 12 months of modification, Number of Loans | loans	1	0	1	0
Restructured loans with payment default within 12 months of modification, Period End Balance	$ 41,000	$ 0	$ 41,000	$ 0
Number of Restructured Loans | loans	205		205		214
Total restructured loans	$ 27,800,000		$ 27,800,000		$ 23,900,000
Restructured loans on accrual status	21,839,000		21,839,000		17,545,000
Restructured Loans, Nonaccrual Status	5,900,000		5,900,000		6,400,000
Allowance for loan and lease losses lncluded in reserves for restructured loans	1,100,000		1,100,000		1,300,000
Restructured loans uncollectible portion written off	100,000	$ 100,000
Accruing TDRs performing in accordance with restructured terms for more than one year	$ 13,100,000		$ 13,100,000		$ 17,200,000
Restructured loans performance threshold (days) | d			90
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	8	4	12	6
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 6,221,000	$ 2,177,000	$ 7,149,000	$ 5,679,000
Restructured loans, Period End Balance	$ 6,183,000	$ 2,183,000	$ 7,096,000	$ 5,624,000
Construction real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0	$ 0	$ 0
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	4	6	6	6
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 2,047,000	$ 1,506,000	$ 2,119,000	$ 1,506,000
Restructured loans, Period End Balance	$ 2,016,000	$ 1,449,000	$ 2,088,000	$ 1,449,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	1	0	3	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 201,000	$ 0	$ 294,000	$ 0
Restructured loans, Period End Balance	$ 201,000	$ 0	294,000	$ 0
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	0	0	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0	$ 0	$ 0
Installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restructured loans, Number of Loans | loans	0	0	0	0
Restructured loans, Restructured loans, Pre-Modification Loan Balance	$ 0	$ 0	$ 0	$ 0
Restructured loans, Period End Balance	$ 0	$ 0	$ 0	$ 0

LOANS AND LEASES - Nonaccrual,

LOANS AND LEASES - Nonaccrual, Restructured and Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Average current balance	$ 53,765	$ 59,910	$ 49,716	$ 55,543
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	17	26	28	52
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	318	306	511	648
Nonaccrual loans	40,462		40,462		$ 24,082
Accruing trouble debt restructurings	21,839		21,839		17,545
Total impaired loans	62,301		62,301		41,627
Restructured loans - nonaccrual status	5,900		5,900		6,400
Interest income effect
Gross amount of interest that would have been recorded under original terms	1,132	1,158	1,934	1,974
Interest included in income
Nonaccrual loans	146	163	226	305
Troubled debt restructurings	189	169	313	395
Total interest included in income	335	332	539	700
Net impact on interest income	797	826	1,395	1,274
Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	10,023	19,499	9,125	16,701
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	6	11	6	24
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	73	87	99	196
Nonaccrual loans	3,448		3,448		5,229
Total impaired loans	11,235		11,235		7,331
Interest included in income
Total interest included in income	79	98	105	220
Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	0	98	27	149
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	0	1	0	2
Nonaccrual loans	0		0		82
Total impaired loans	0		0		82
Interest included in income
Total interest included in income	0	1	0	2
Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	25	1,075	26	538
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	0	2	0
Nonaccrual loans	24		24		29
Total impaired loans	24		24		29
Interest included in income
Total interest included in income	1	0	2	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	27,874	26,123	25,763	24,313
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	3	8	6	13
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	140	144	239	304
Nonaccrual loans	21,593		21,593		10,616
Total impaired loans	31,011		31,011		21,542
Interest included in income
Total interest included in income	143	152	245	317
Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	10,215	8,731	9,454	9,217
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	7	6	14	13
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	76	46	123	92
Nonaccrual loans	9,278		9,278		4,140
Total impaired loans	13,255		13,255		7,932
Interest included in income
Total interest included in income	83	52	137	105
Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	5,323	4,027	5,033	4,212
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	1	1	2	2
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	27	27	47	51
Nonaccrual loans	5,820		5,820		3,743
Total impaired loans	6,472		6,472		4,456
Interest included in income
Total interest included in income	28	28	49	53
Installment
Financing Receivable, Modifications [Line Items]
Average current balance	305	357	288	413
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	1	1	3
Nonaccrual loans	299		299		243
Total impaired loans	304		304		255
Interest included in income
Total interest included in income	1	1	1	3
Loans with no related allowance recorded [member]
Financing Receivable, Modifications [Line Items]
Average current balance	51,955	55,724	47,029	48,789
Total impaired loans	60,427		60,427		37,183
Loans with no related allowance recorded [member] | Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	9,714	17,198	8,863	15,607
Total impaired loans	10,856		10,856		7,162
Loans with no related allowance recorded [member] | Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	0	98	27	149
Total impaired loans	0		0		82
Loans with no related allowance recorded [member] | Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	25	1,075	26	538
Total impaired loans	24		24		29
Loans with no related allowance recorded [member] | Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	27,516	25,465	24,485	19,939
Total impaired loans	30,655		30,655		18,423
Loans with no related allowance recorded [member] | Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	9,173	7,605	8,407	8,032
Total impaired loans	12,216		12,216		6,876
Loans with no related allowance recorded [member] | Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	5,222	3,926	4,933	4,111
Total impaired loans	6,372		6,372		4,356
Loans with no related allowance recorded [member] | Installment
Financing Receivable, Modifications [Line Items]
Average current balance	305	357	288	413
Total impaired loans	304		304		255
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Total impaired loans	1,874		1,874
Impaired Financing Receivables With Related Allowance [Member] | Commercial
Financing Receivable, Modifications [Line Items]
Average current balance	309	2,301	262	1,094
Total impaired loans	379		379		169
Impaired Financing Receivables With Related Allowance [Member] | Lease financing
Financing Receivable, Modifications [Line Items]
Average current balance	0	0	0	0
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member] | Construction real estate
Financing Receivable, Modifications [Line Items]
Average current balance	0	0	0	0
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member] | Commercial real estate
Financing Receivable, Modifications [Line Items]
Average current balance	358	658	1,278	4,374
Total impaired loans	356		356		3,119
Impaired Financing Receivables With Related Allowance [Member] | Residential real estate
Financing Receivable, Modifications [Line Items]
Average current balance	1,042	1,126	1,047	1,185
Total impaired loans	1,039		1,039		1,056
Impaired Financing Receivables With Related Allowance [Member] | Home equity
Financing Receivable, Modifications [Line Items]
Average current balance	101	101	100	101
Total impaired loans	100		100		100
Impaired Financing Receivables With Related Allowance [Member] | Installment
Financing Receivable, Modifications [Line Items]
Average current balance	0	0	0	0
Total impaired loans	0		0		0
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Modifications [Line Items]
Average current balance	$ 1,810	$ 4,186	$ 2,687	$ 6,754
Total impaired loans					$ 4,444

LOANS AND LEASES - Investment i

LOANS AND LEASES - Investment in Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 40,462		$ 40,462		$ 24,082
Current balance	62,301		62,301		41,627
Contractual Principal Balance	75,296		75,296		47,857
Related Allowance	366		366		779
Average current balance	53,765	$ 59,910	49,716	$ 55,543
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	17	26	28	52
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	318	306	511	648
Interest income recognized	335	332	539	700
Commercial
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,448		3,448		5,229
Current balance	11,235		11,235		7,331
Contractual Principal Balance	15,026		15,026		8,629
Related Allowance	179		179		169
Average current balance	10,023	19,499	9,125	16,701
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	6	11	6	24
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	73	87	99	196
Interest income recognized	79	98	105	220
Lease financing
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0		0		82
Current balance	0		0		82
Contractual Principal Balance	0		0		82
Related Allowance	0		0		0
Average current balance	0	98	27	149
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	0	1	0	2
Interest income recognized	0	1	0	2
Construction real estate
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	24		24		29
Current balance	24		24		29
Contractual Principal Balance	57		57		60
Related Allowance	0		0		0
Average current balance	25	1,075	26	538
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	0	2	0
Interest income recognized	1	0	2	0
Commercial real estate
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	21,593		21,593		10,616
Current balance	31,011		31,011		21,542
Contractual Principal Balance	36,777		36,777		23,957
Related Allowance	25		25		448
Average current balance	27,874	26,123	25,763	24,313
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	3	8	6	13
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	140	144	239	304
Interest income recognized	143	152	245	317
Residential real estate
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	9,278		9,278		4,140
Current balance	13,255		13,255		7,932
Contractual Principal Balance	15,422		15,422		9,208
Related Allowance	160		160		160
Average current balance	10,215	8,731	9,454	9,217
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	7	6	14	13
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	76	46	123	92
Interest income recognized	83	52	137	105
Home equity
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	5,820		5,820		3,743
Current balance	6,472		6,472		4,456
Contractual Principal Balance	7,411		7,411		5,499
Related Allowance	2		2		2
Average current balance	5,323	4,027	5,033	4,212
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	1	1	2	2
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	27	27	47	51
Interest income recognized	28	28	49	53
Installment
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	299		299		243
Current balance	304		304		255
Contractual Principal Balance	603		603		422
Related Allowance	0		0		0
Average current balance	305	357	288	413
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	0	0	0	0
Impaired Financing Receivable, with No Related Allowance, Interest Income, Accrual Method	1	1	1	3
Interest income recognized	1	1	1	3
Loans with no related allowance recorded [member]
Financing Receivable, Impaired [Line Items]
Current balance	60,427		60,427		37,183
Contractual Principal Balance	73,422		73,422		43,405
Related Allowance	0		0		0
Average current balance	51,955	55,724	47,029	48,789
Loans with no related allowance recorded [member] | Commercial
Financing Receivable, Impaired [Line Items]
Current balance	10,856		10,856		7,162
Contractual Principal Balance	14,647		14,647		8,460
Related Allowance	0		0		0
Average current balance	9,714	17,198	8,863	15,607
Loans with no related allowance recorded [member] | Lease financing
Financing Receivable, Impaired [Line Items]
Current balance	0		0		82
Contractual Principal Balance	0		0		82
Related Allowance	0		0		0
Average current balance	0	98	27	149
Loans with no related allowance recorded [member] | Construction real estate
Financing Receivable, Impaired [Line Items]
Current balance	24		24		29
Contractual Principal Balance	57		57		60
Related Allowance	0		0		0
Average current balance	25	1,075	26	538
Loans with no related allowance recorded [member] | Commercial real estate
Financing Receivable, Impaired [Line Items]
Current balance	30,655		30,655		18,423
Contractual Principal Balance	36,421		36,421		20,837
Related Allowance	0		0		0
Average current balance	27,516	25,465	24,485	19,939
Loans with no related allowance recorded [member] | Residential real estate
Financing Receivable, Impaired [Line Items]
Current balance	12,216		12,216		6,876
Contractual Principal Balance	14,383		14,383		8,145
Related Allowance	0		0		0
Average current balance	9,173	7,605	8,407	8,032
Loans with no related allowance recorded [member] | Home equity
Financing Receivable, Impaired [Line Items]
Current balance	6,372		6,372		4,356
Contractual Principal Balance	7,311		7,311		5,399
Related Allowance	0		0		0
Average current balance	5,222	3,926	4,933	4,111
Loans with no related allowance recorded [member] | Installment
Financing Receivable, Impaired [Line Items]
Current balance	304		304		255
Contractual Principal Balance	603		603		422
Related Allowance	0		0		0
Average current balance	305	357	288	413
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Current balance	1,874		1,874
Contractual Principal Balance	1,874		1,874
Related Allowance	366		366
Impaired Financing Receivables With Related Allowance [Member] | Commercial
Financing Receivable, Impaired [Line Items]
Current balance	379		379		169
Contractual Principal Balance	379		379		169
Related Allowance	179		179		169
Average current balance	309	2,301	262	1,094
Impaired Financing Receivables With Related Allowance [Member] | Lease financing
Financing Receivable, Impaired [Line Items]
Current balance	0		0		0
Contractual Principal Balance	0		0		0
Related Allowance	0		0		0
Average current balance	0	0	0	0
Impaired Financing Receivables With Related Allowance [Member] | Construction real estate
Financing Receivable, Impaired [Line Items]
Current balance	0		0		0
Contractual Principal Balance	0		0		0
Related Allowance	0		0		0
Average current balance	0	0	0	0
Impaired Financing Receivables With Related Allowance [Member] | Commercial real estate
Financing Receivable, Impaired [Line Items]
Current balance	356		356		3,119
Contractual Principal Balance	356		356		3,120
Related Allowance	25		25		448
Average current balance	358	658	1,278	4,374
Impaired Financing Receivables With Related Allowance [Member] | Residential real estate
Financing Receivable, Impaired [Line Items]
Current balance	1,039		1,039		1,056
Contractual Principal Balance	1,039		1,039		1,063
Related Allowance	160		160		160
Average current balance	1,042	1,126	1,047	1,185
Impaired Financing Receivables With Related Allowance [Member] | Home equity
Financing Receivable, Impaired [Line Items]
Current balance	100		100		100
Contractual Principal Balance	100		100		100
Related Allowance	2		2		2
Average current balance	101	101	100	101
Impaired Financing Receivables With Related Allowance [Member] | Installment
Financing Receivable, Impaired [Line Items]
Current balance	0		0		0
Contractual Principal Balance	0		0		0
Related Allowance	0		0		0
Average current balance	0	0	0	0
Impaired Financing Receivables With Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Current balance					4,444
Contractual Principal Balance					4,452
Related Allowance					$ 779
Average current balance	$ 1,810	$ 4,186	$ 2,687	$ 6,754

LOANS AND LEASES - Changes in O

LOANS AND LEASES - Changes in Other Real Estate Owned (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 1,065	$ 5,300	$ 2,781	$ 6,284
Additions	1,545	1,963	2,174	2,250
Disposals	(618)	(1,130)	(2,840)	(2,292)
Write-downs	139	172	262	281
Balance at end of period	1,853	5,961	1,853	5,961
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additions	1,020	50	1,190	172
Disposals	(326)	(682)	(2,430)	(1,607)
Write-downs	0	116	97	162
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Additions	525	1,913	984	2,078
Disposals	(292)	(448)	(410)	(685)
Write-downs	$ 139	$ 56	$ 165	$ 119

ALLOWANCE FOR LOAN AND LEASE 49

ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in the Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Allowance for loan and lease losses:
Balance at beginning of period	$ 54,380	$ 56,326	$ 54,021	$ 57,961
Provision for loan and lease losses	3,735	467	6,038	834
Loans charged-off	(5,822)	(4,498)	(9,491)	(7,248)
Recoveries	1,783	2,578	3,508	3,326
Total net charge-offs	4,039	1,920	5,983	3,922
Balance at end of period	54,076	54,873	54,076	54,873
Ending allowance on loans individually evaluated for impairment					$ 366	$ 779
Ending allowance on loans collectively evaluated for impairment					53,710	53,242
Ending allowance for loan and lease losses	54,380	56,326	54,021	54,873	54,076	54,021
Loans and Leases:
Ending balance of loans individually evaluated for impairment					62,301	41,627
Ending balance of loans collectively evaluated for impairment					8,822,280	5,971,556
Loans and Leases Receivable, Net of Deferred Income					8,884,581	6,013,183
Commercial
Allowance for loan and lease losses:
Balance at beginning of period	18,038	17,148	17,598	19,225
Provision for loan and lease losses	3,328	3,537	4,217	2,941
Loans charged-off	(4,356)	(3,065)	(5,241)	(4,808)
Recoveries	518	693	954	955
Total net charge-offs	3,838	2,372	4,287	3,853
Balance at end of period	17,528	18,313	17,528	18,313
Ending allowance on loans individually evaluated for impairment					179	169
Ending allowance on loans collectively evaluated for impairment					17,349	17,429
Ending allowance for loan and lease losses	18,038	17,148	17,528	19,225	17,528	17,598
Loans and Leases:
Ending balance of loans individually evaluated for impairment					11,235	7,331
Ending balance of loans collectively evaluated for impairment					2,429,361	1,905,412
Loans and Leases Receivable, Net of Deferred Income					2,440,596	1,912,743
Lease financing
Allowance for loan and lease losses:
Balance at beginning of period	626	616	675	716
Provision for loan and lease losses	170	(67)	121	(167)
Loans charged-off	0	0	0	0
Recoveries	1	1	1	1
Total net charge-offs	(1)	(1)	(1)	(1)
Balance at end of period	797	550	797	550
Ending allowance on loans individually evaluated for impairment					0	0
Ending allowance on loans collectively evaluated for impairment					797	675
Ending allowance for loan and lease losses	626	616	797	716	797	675
Loans and Leases:
Ending balance of loans individually evaluated for impairment					0	82
Ending balance of loans collectively evaluated for impairment					96,198	89,265
Loans and Leases Receivable, Net of Deferred Income					96,198	89,347
Construction real estate
Allowance for loan and lease losses:
Balance at beginning of period	4,267	3,607	3,577	3,282
Provision for loan and lease losses	(282)	(280)	408	45
Loans charged-off	0	0	0	0
Recoveries	0	89	0	89
Total net charge-offs	0	(89)	0	(89)
Balance at end of period	3,985	3,416	3,985	3,416
Ending allowance on loans individually evaluated for impairment					0	0
Ending allowance on loans collectively evaluated for impairment					3,985	3,577
Ending allowance for loan and lease losses	4,267	3,607	3,985	3,416	3,985	3,577
Loans and Leases:
Ending balance of loans individually evaluated for impairment					24	29
Ending balance of loans collectively evaluated for impairment					555,444	467,701
Loans and Leases Receivable, Net of Deferred Income					555,468	467,730
Commercial real estate
Allowance for loan and lease losses:
Balance at beginning of period	20,321	23,745	20,930	26,540
Provision for loan and lease losses	(619)	(2,941)	196	(5,507)
Loans charged-off	(78)	(485)	(2,254)	(970)
Recoveries	887	1,398	1,639	1,654
Total net charge-offs	(809)	(913)	615	(684)
Balance at end of period	20,511	21,717	20,511	21,717
Ending allowance on loans individually evaluated for impairment					25	448
Ending allowance on loans collectively evaluated for impairment					20,486	20,482
Ending allowance for loan and lease losses	20,321	23,745	20,511	21,717	20,511	20,930
Loans and Leases:
Ending balance of loans individually evaluated for impairment					31,011	21,542
Ending balance of loans collectively evaluated for impairment					3,857,982	2,468,549
Loans and Leases Receivable, Net of Deferred Income					3,888,993	2,490,091
Residential real estate
Allowance for loan and lease losses:
Balance at beginning of period	4,727	5,485	4,683	3,208
Provision for loan and lease losses	(28)	(305)	86	2,024
Loans charged-off	(101)	(223)	(197)	(284)
Recoveries	70	59	96	68
Total net charge-offs	31	164	101	216
Balance at end of period	4,668	5,016	4,668	5,016
Ending allowance on loans individually evaluated for impairment					160	160
Ending allowance on loans collectively evaluated for impairment					4,508	4,523
Ending allowance for loan and lease losses	4,727	5,485	4,668	5,016	4,668	4,683
Loans and Leases:
Ending balance of loans individually evaluated for impairment					13,255	7,932
Ending balance of loans collectively evaluated for impairment					905,649	463,459
Loans and Leases Receivable, Net of Deferred Income					918,904	471,391
Home equity
Allowance for loan and lease losses:
Balance at beginning of period	4,828	3,774	4,935	3,043
Provision for loan and lease losses	171	526	(123)	1,331
Loans charged-off	(385)	(384)	(627)	(564)
Recoveries	187	222	616	328
Total net charge-offs	198	162	11	236
Balance at end of period	4,801	4,138	4,801	4,138
Ending allowance on loans individually evaluated for impairment					2	2
Ending allowance on loans collectively evaluated for impairment					4,799	4,933
Ending allowance for loan and lease losses	4,828	3,774	4,935	3,043	4,801	4,935
Loans and Leases:
Ending balance of loans individually evaluated for impairment					6,472	4,456
Ending balance of loans collectively evaluated for impairment					828,559	489,148
Loans and Leases Receivable, Net of Deferred Income					835,031	493,604
Installment
Allowance for loan and lease losses:
Balance at beginning of period	290	419	307	388
Provision for loan and lease losses	136	19	87	28
Loans charged-off	(218)	(126)	(234)	(175)
Recoveries	82	43	130	114
Total net charge-offs	136	83	104	61
Balance at end of period	290	355	290	355
Ending allowance on loans individually evaluated for impairment					0	0
Ending allowance on loans collectively evaluated for impairment					290	307
Ending allowance for loan and lease losses	290	419	290	355	290	307
Loans and Leases:
Ending balance of loans individually evaluated for impairment					304	255
Ending balance of loans collectively evaluated for impairment					100,422	41,331
Loans and Leases Receivable, Net of Deferred Income					100,726	41,586
Credit card
Allowance for loan and lease losses:
Balance at beginning of period	1,283	1,532	1,316	1,559
Provision for loan and lease losses	859	(22)	1,046	139
Loans charged-off	(684)	(215)	(938)	(447)
Recoveries	38	73	72	117
Total net charge-offs	646	142	(866)	(330)
Balance at end of period	1,496	1,368	1,496	1,368
Ending allowance on loans individually evaluated for impairment					0	0
Ending allowance on loans collectively evaluated for impairment					1,496	1,316
Ending allowance for loan and lease losses	$ 1,283	$ 1,532	$ 1,496	$ 1,368	1,496	1,316
Loans and Leases:
Ending balance of loans individually evaluated for impairment					0	0
Ending balance of loans collectively evaluated for impairment					48,665	46,691
Loans and Leases Receivable, Net of Deferred Income					$ 48,665	$ 46,691

GOODWILL AND OTHER INTANGIBLE50

GOODWILL AND OTHER INTANGIBLE ASSETS GOODWILL AND OTHER INTANGIBLE ASSETS--Schedule of Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Goodwill [Roll Forward]
Balance at beginning of period	$ 204,084	$ 204,084	$ 204,084
Goodwill	678,941	$ 0	0
Balance at end of period	$ 883,025		$ 204,084

GOODWILL AND OTHER INTANGIBLE51

GOODWILL AND OTHER INTANGIBLE ASSETS--Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 883,025		$ 883,025		$ 204,084	$ 204,084
Intangible Assets, Net (Excluding Goodwill)	51,600		51,600		5,300
Finite-Lived Core Deposits, Gross	42,500		42,500		$ 3,300
Finite-Lived Intangible Assets, Amortization Expense	$ 2,400	$ 300	$ 2,600	$ 700
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets amortization method			accelerated basis
Estimated weighted average life (in years)			9 years 3 months 18 days

BORROWINGS Borrowings - - Addit

BORROWINGS Borrowings - - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Federal Home Loan Bank short-term borrowings	$ 1,100,233	$ 742,300
Line of Credit Facility, Maximum Borrowing Capacity	15,000
Commitments outstanding to extend credit	0	0
Short-term Debt	1,188,303	814,565
Long-term Debt	469,423	119,654
Subordinated debt	$ 120,000
Subordinated Borrowing, Interest Rate	5.125%
Subordinated debt	$ 177,887	120,000
Advances from Federal Home Loan Banks	$ 299,580	$ 241
Federal Home Loan Bank	1.90%	1.09%
Subordinated Debt [Member]
Subordinated debt	$ 49,500
Short-term Debt [Member]
Short-term Debt	$ 8,300
Debt Instrument, Interest Rate, Stated Percentage	4.19%
Private Placement [Member]
Subordinated debt	$ 8,400
Debt Instrument, Interest Rate, Effective Percentage	6.95%
Subordinated Debt [Member]
Debt Instrument Maturity Period	30 years
DebtInstrumentMinimumCallablePeriod	5 years

BORROWINGS - Schedule of Long-t

BORROWINGS - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Amount
Subordinated debt	$ 177,887	$ 120,000
FHLB long-term advances	299,580	241
Capital loan with municipality	775	775
Total long-term debt	$ 469,423	$ 119,654
Average Rate [Abstract]
Debt, Weighted Average Interest Rate	5.13%	5.13%
Federal Home Loan Bank	1.90%	1.09%
Weighted average rate on other long-term debt	0.00%	0.00%
Total long-term debt	3.16%	5.14%
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (8,819)	$ (1,362)

ACCUMULATED OTHER COMPREHENSI54

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Other Comprehensive Income (Loss), before Reclassification Adjustments and Tax [Abstract]
Unrealized gain (loss) on investment securities	$ (11,456)	$ 7,170	$ (23,992)	$ 10,002
Unrealized gain (loss) on derivatives	203	202	405	405
Retirement obligation	0	0	0	0
Total	(11,253)	7,372	(23,587)	10,407
Other Comprehensive Income (Loss) Reclassifications before Tax [Abstract]
Unrealized gain (loss) on investment securities	(30)	838	(30)	1,354
Unrealized gain (loss) on derivatives	0	0	0	0
Retirement obligation	(452)	(335)	(871)	(670)
Total	(482)	503	(901)	684
Transactions Pre-tax
Unrealized gain (loss) on investment securities	(11,426)	6,332	(23,962)	8,648
Unrealized gain (loss) on derivatives	203	202	405	405
Unfunded pension obligation	452	335	871	670
Total	(10,771)	6,869	(22,686)	9,723
Transactions Tax-effect
Unrealized gain (loss) on investment securities	2,448	(2,256)	5,154	(3,085)
Unrealized gain (loss) on derivatives	(44)	(74)	(90)	(149)
Retirement obligation	42	(122)	(54)	(268)
Total	2,446	(2,452)	5,010	(3,502)
Transactions Net of tax
Unrealized gain (loss) on investment securities	(8,978)	4,076	(18,808)	5,563
Unrealized gain (loss) on derivatives	159	128	315	256
Retirement obligation	494	213	817	402
Total	(8,325)	4,417	(17,676)	6,221
Stranded Tax Effects
Unrealized gain (loss) on investment securities			(39)
Unrealized gain (loss) on Derivatives			(124)
Retirement obligation			(4,779)
Total			(4,942)
Balances Net of tax
Unrealized gain (loss) on investment securities	(19,029)	1,014	(19,029)	1,014	$ (10,051)	$ (182)	$ (3,062)	$ (4,549)
Unrealized gain (loss) on cash flow hedges	(386)	(835)	(386)	(835)	(545)	(577)	(963)	(1,091)
Retirement obligation	(23,593)	(22,401)	(23,593)	(22,401)	(24,087)	(19,631)	(22,614)	(22,803)
Total	$ (43,008)	$ (22,222)	(43,008)	(22,222)	$ (34,683)	$ (20,390)	$ (26,639)	$ (28,443)
Accumulated other comprehensive income (loss)
Transactions Net of tax
Total			$ (17,676)	$ 6,221

ACCUMULATED OTHER COMPREHENSI55

ACCUMULATED OTHER COMPREHENSIVE INCOME AMOUNT RECLASSIFIED FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Accumulated Comprehensive income reclassified from AOCI [Line Items]
Net gain (loss) on sales of investment securities	$ (30)	$ 838	$ (30)	$ 1,354
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	103	104	206	207
Defined Benefit Plan, Amortization of Gain (Loss)	(555)	(439)	(1,077)	(877)
Other Comprehensive Income, Reclassification, Amortization of Defined Benefit Plans items, Pre-tax	(452)	(335)	(871)	(670)
Total	$ (482)	$ 503	$ (901)	$ 684

DERIVATIVES - Additional Inform

DERIVATIVES - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)entity	Dec. 31, 2017USD ($)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
Inerest-bearing deposit liability	$ 2,358,312	$ 1,674,080
Number of counterparties | entity	14	13
Derivative Asset	$ 27,567	$ 12,682
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	27,565	12,687
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	37,200	12,300
Other Credit Derivatives [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	35,600	15,400
Credit Risk Derivative Liabilities, at Fair Value		100
Credit Risk Contract [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	146,300	95,900
Credit Risk Derivative Liabilities, at Fair Value	100	54
Accrued interest and other liabilities | Derivative [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	1,200,000	837,500
Derivative Asset	$ (21,800)
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		$ 1,300

DERIVATIVES - Summary of Deriva

DERIVATIVES - Summary of Derivative Financial Instruments and Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	$ 2,358,312	$ 1,674,080
Derivative Asset	27,567	12,682
Estimate Fair Value Loss	(27,565)	(12,687)
Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	35,600	15,400
Credit Risk Derivative Liabilities, at Fair Value		100
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	1,179,156	837,040
Derivative Asset	24,306	5,529
Estimate Fair Value Loss	(3,259)	(7,158)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other assets
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	1,179,156	837,040
Derivative Asset	3,261	7,153
Estimate Fair Value Loss	$ (24,306)	$ (5,529)

DERIVATIVES DERIVATIVES - Discl

DERIVATIVES DERIVATIVES - Disclosure by Type of Financial Instrument (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Credit Risk Contract [Member]
Derivatives, Fair Value [Line Items]
Credit Risk Derivative Liabilities, at Fair Value	$ 100	$ 54
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	27,567	12,687
Derivative Liability, Fair Value, Gross Asset	(7,152)	2,279
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 20,415	$ 14,966

DERIVATIVES - Derivative Financ

DERIVATIVES - Derivative Financial Instruments, Average Remaining Maturity and the Weighted-Average Interest Rates being Paid and Received (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional Value	$ 2,358,312	$ 1,674,080
Interest Rate Swap
Derivative [Line Items]
Notional Value	$ 2,358,312
Average Maturity (years)	4 years 9 months 18 days
Fair Value	$ 2
Weighted-Average Rate Receive	4.37%
Weighted-Average Rate Pay	4.37%
Interest Rate Swap | Derivative Financial Instruments Receive Fixed Pay Variable
Derivative [Line Items]
Notional Value	$ 1,179,156
Average Maturity (years)	4 years 9 months 18 days
Fair Value	$ (21,045)
Weighted-Average Rate Receive	4.50%
Weighted-Average Rate Pay	4.25%
Interest Rate Swap | Derivative Financial Instruments Receive Variable Pay Fixed
Derivative [Line Items]
Notional Value	$ 1,179,156
Average Maturity (years)	4 years 9 months 18 days
Fair Value	$ 21,047
Weighted-Average Rate Receive	4.25%
Weighted-Average Rate Pay	4.50%

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Commitments and Contingencies Disclosure [Line Items]
Reserves for unfunded commitments	$ 1,100		$ 1,100		$ 500
Commitments outstanding to extend credit	0		0		0
Letters of credit issued to guarantee performance of a client to a third party	35,600		35,600		25,300
Affordable Housing Program Obligation	34,300		34,300		35,900
Affordable housing contingent commitment	0		0		0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	2,900		2,900		3,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	2,900		2,900		3,000
Amortization Method Qualified Affordable Housing Project Investments, Amortization	1,600	$ 1,200	2,800	$ 2,200
Estimated Litigation Liability	0		0		0
Loans and Leases Receivable, Commitments, Fixed Rates			215,800		44,300
Loans and Leases Receivable, Commitments, Variable Rates			$ 2,600,000		2,000,000
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			30 years
Commitments to Extend Credit
Commitments and Contingencies Disclosure [Line Items]
Commitments outstanding to extend credit	2,900,000		$ 2,900,000		$ 2,100,000
Affordable housing investment [Member]
Commitments and Contingencies Disclosure [Line Items]
Low-income housing tax credit	1,200	800	2,300	1,600
Historic tax credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Low-income housing tax credit	$ 100	$ 100	$ 200	$ 300

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 9,327	$ 11,215	$ 16,980	$ 21,685
Effective tax rate	20.40%	33.00%	20.20%	31.50%
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 100	$ 0		$ 1,200
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	35.00%
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 2,900		$ 2,900		$ 2,900

EMPLOYEE BENEFIT PLANS - Additi

EMPLOYEE BENEFIT PLANS - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 0		$ 0
Payment for Pension Benefits			0		$ 0
Pension Cost (Reversal of Cost)	$ 338,000	$ (318,000)	$ 182,000	$ (637,000)

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS - Employee benefit plan amounts recognized in the Consolidated Balance Sheets and Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Retirement Benefits [Abstract]
Service cost	$ 1,735	$ 1,239	$ 3,030	$ 2,477
Interest cost	601	589	1,191	1,178
Expected return on plan assets	(2,450)	(2,481)	(4,910)	(4,962)
Amortization of prior service cost	(103)	(104)	(206)	(207)
Defined Benefit Plan, Amortization of Gain (Loss)	555	439	1,077	877
Net periodic benefit cost (income)	$ 338	$ (318)	$ 182	$ (637)

REVENUE RECOGNITION REVENUE REC

REVENUE RECOGNITION REVENUE RECOGNITION (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Revenue Recognition [Abstract]
Fees and Commissions, Credit and Debit Cards	$ 8.1	$ 13.5
Credit card expense	$ 2.8	$ 4.8

EARNINGS PER COMMON SHARE - Com

EARNINGS PER COMMON SHARE - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator for basic and diluted earnings per share -income available to common shareholders:
Net income	$ 36,418	$ 22,736	$ 66,924	$ 47,150
Denominator for basic earnings per share - weighted average shares	97,347,533	61,543,478	79,599,709	61,471,347
Effect of dilutive securities -
Employee stock awards	545,374	625,031	504,914	649,706
Warrants	539,165	65,513	524,872	66,420
Denominator for diluted earnings per share - adjusted weighted average shares	98,432,072	62,234,022	80,629,495	62,187,473
Basic	$ 0.37	$ 0.37	$ 0.84	$ 0.77
Diluted	$ 0.37	$ 0.37	$ 0.83	$ 0.76

EARNINGS PER COMMON SHARE - Add

EARNINGS PER COMMON SHARE - Additional Information (Details) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share Disclosure [Line Items]
Investment Warrants, Exercise Price	$ 12.11
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	22,698	112,233
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
MainSource [Member]
Earnings Per Share Disclosure [Line Items]
Investment Warrants, Exercise Price	$ 10.72
MainSource [Member] | 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	793,520

FAIR VALUE DISCLOSURES - Estima

FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 27,565	$ 12,687
Financial assets
Investment securities held-to-maturity	443,957	654,008
Other investments	95,004	53,140
Deposits
Noninterest-bearing	2,471,932	1,662,058
Savings	3,087,683	2,462,420
Time	2,104,044	1,317,105
Carrying value
Financial assets
Cash and short-term investments	254,582	184,624
Investment securities held-to-maturity	443,957	654,008
Other investments	95,004	53,140
Loans held for sale	15,821	11,502
Loans and leases	8,830,505	5,959,162
Interest Receivable	40,152	24,496
Deposits
Deposits	10,103,747	6,895,046
Short-term borrowings	1,188,303	814,565
Long-term debt	469,423	119,654
Interest Payable	9,550	5,104
Fair value
Financial assets
Cash and short-term investments	254,582	184,624
Investment securities held-to-maturity	435,785	653,101
Loans held for sale	15,821	11,502
Loans and leases	8,847,519	6,006,656
Interest Receivable	40,152	24,496
Deposits
Deposits	10,073,140	6,884,615
Short-term borrowings	1,188,303	814,565
Long-term debt	462,478	117,908
Interest Payable	9,550	5,104
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	254,582	184,624
Investment securities held-to-maturity	0	0
Loans held for sale	0	0
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	1,188,303	814,565
Long-term debt	0	0
Interest Payable	1,577	204
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	435,785	653,101
Loans held for sale	15,821	11,502
Loans and leases	0	0
Interest Receivable	13,939	8,265
Deposits
Deposits	10,073,140	6,884,615
Short-term borrowings	0	0
Long-term debt	462,478	117,908
Interest Payable	7,973	4,900
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	8,847,519	6,006,656
Interest Receivable	26,213	16,231
Deposits
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 (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Derivatives	$ 27,567	$ 12,682
Investment securities available-for-sale	2,654,909	1,349,408
Liabilities
Derivatives	27,565	12,687
Fair Value, Measurements, Recurring
Assets
Derivatives	28,113	12,757
Investment securities available-for-sale	2,654,909	1,349,408
Total	2,683,022	1,362,165
Liabilities
Derivatives	27,624	12,755
Fair Value, Measurements, Recurring | Fair Value Measurements Using Level 1
Assets
Derivatives	0	0
Investment securities available-for-sale	7,737	2,969
Total	7,737	2,969
Liabilities
Derivatives	0	0
Fair Value, Measurements, Recurring | Fair Value Measurements Using Level 2
Assets
Derivatives	28,113	12,757
Investment securities available-for-sale	2,647,172	1,346,439
Total	2,675,285	1,359,196
Liabilities
Derivatives	27,624	12,755
Fair Value, Measurements, Recurring | Fair Value Measurements Using Level 3
Assets
Derivatives	0	0
Investment securities available-for-sale	0	0
Total	0	0
Liabilities
Derivatives	$ 0	$ 0

FAIR VALUE DISCLOSURES - Summ69

FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Measurements Using Level 1
Assets
Impaired loans	$ 0	$ 0
Other Real Estate Owned, Fair Value Disclosure	0	0
Fair Value Measurements Using Level 2
Assets
Impaired loans	0	0
Other Real Estate Owned, Fair Value Disclosure	0	0
Fair Value Measurements Using Level 3
Assets
Impaired loans	531	2,671
Other Real Estate Owned, Fair Value Disclosure	$ 284	$ 1,086

BUSINESS COMBINATION BUSINESS C

BUSINESS COMBINATION BUSINESS COMBINATION - Additional Information (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Business Acquisition, Number Of Shares Received by Acquiree	1.3875
Business Combination, Consideration Transferred	$ 1,100,000	$ 1,061,956
Goodwill		678,941	$ 0	$ 0
Payments for Merger Related Costs		$ 25,900

BUSINESS COMBINATION BUSINESS71

BUSINESS COMBINATION BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Cash consideration		$ 43
Stock consideration		1,045,876
Warrant consideration		14,460
Options consideration		1,577
Total purchase consideration	$ 1,100,000	1,061,956
Cash		71,681
Investment securities available for sale		901,008
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Held to Maturity Securities		171,423
Other investments		28,763
Loans		2,791,954
Premises and equipment		99,098
Other real estate owned		1,361
Intangible assets		41,750
Other assets		155,945
Assets held for sale		127,775
Total assets acquired		4,390,758
Deposits		3,264,038
Subordinated notes		49,027
FHLB advances		291,887
Other borrowings		205,620
Other liabilities		21,449
Liabilities held for sale		175,722
Total liabilities assumed		4,007,743		$ 0
Net identifiable assets		383,015
Goodwill		$ 678,941	$ 0	$ 0

BUSINESS COMBINATION Business A

BUSINESS COMBINATION Business Acquisition, Pro Forma Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Business Acquisition, Pro Forma Revenue	$ 242,130	$ 219,984
Business Acquisition, Pro Forma Net Income (Loss)	$ 106,556	$ 58,755
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 1.09	$ 0.61
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 1.08	$ 0.60