First Merchants (FRME) 10-K 1 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 22, 2018	Jun. 30, 2017
Document Documentand Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	FRME
Entity Registrant Name	FIRST MERCHANTS CORP
Entity Central Index Key	712,534
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		49,540,866
Entity Public Float			$ 1,732,182,000

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 154,905	$ 127,927
Interest-bearing time deposits	35,027	24,459
Investment securities available for sale	999,947	696,862
Investment securities held to maturity (fair value of $568,208 and $611,933)	560,655	607,643
Loans held for sale	7,216	2,929
Loans	6,751,199	5,139,645
Less: Allowance for loan losses	(75,032)	(66,037)
Net Loans	6,676,167	5,073,608
Premises and equipment	95,852	94,432
Federal Home Loan Bank stock	23,825	17,964
Interest receivable	37,130	26,194
Other intangibles	31,148	14,866
Goodwill	445,355	244,000
Cash surrender value of life insurance	223,557	201,671
Other real estate owned	10,373	8,966
Tax asset, deferred and receivable	23,983	39,384
Other assets	42,338	30,706
TOTAL ASSETS	9,367,478	7,211,611
Deposits:
Noninterest-bearing	1,761,553	1,348,267
Interest-bearing	5,410,977	4,208,231
Total Deposits	7,172,530	5,556,498
Borrowings:
Federal funds purchased	144,038	120,349
Securities sold under repurchase agreements	136,623	146,480
Federal Home Loan Bank advances	414,377	298,923
Subordinated debentures and term loans	139,349	128,445
Total Borrowings	834,387	694,197
Interest payable	4,390	3,110
Other liabilities	52,708	56,149
Total Liabilities	8,064,015	6,309,954
COMMITMENTS AND CONTINGENT LIABILITIES
STOCKHOLDERS' EQUITY
Cumulative Preferred Stock	125	125
Common Stock	6,145	5,114
Additional paid-in capital	834,870	509,018
Retained earnings	465,231	400,981
Accumulated other comprehensive loss	(2,908)	(13,581)
Total Stockholders' Equity	1,303,463	901,657
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 9,367,478	$ 7,211,611

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands		Dec. 31, 2017	May 01, 2017	Apr. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Investment securities held to maturity		$ 568,208			$ 611,933
Preferred Stock, par value (in dollars per share)		$ 1,000			$ 1,000
Preferred Stock, liquidation value (in dollars per share)		$ 1,000			$ 1,000
Preferred Stock, shares authorized		600			600
Preferred Stock, shares issued		125			125
Preferred Stock, shares outstanding		125			125
Common Stock, stated value (in dollars per share)		$ 0.125			$ 0.125
Common Stock, shares authorized	[1]	100,000,000	100,000,000	50,000,000	50,000,000
Common Stock, shares issued		49,158,238			40,912,697
Common Stock, shares outstanding		49,158,238			40,912,697
[1]	On May 1, 2017, the shareholders of First Merchants Corporation approved an amendment to the Articles of Incorporation to increase the number of shares of common stock authorized to issue from 50,000,000 to 100,000,000 shares.

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans receivable:
Taxable	$ 263,704	$ 210,302	$ 180,805
Tax exempt	10,694	6,525	3,459
Investment securities:
Taxable	17,489	16,415	17,885
Tax exempt	21,379	18,622	16,922
Deposits with financial institutions	736	350	160
Federal Reserve and Federal Home Loan Bank stock	894	1,098	1,967
Total Interest Income	314,896	253,312	221,198
INTEREST EXPENSE
Deposits	23,806	15,914	14,855
Federal funds purchased	561	102	74
Securities sold under repurchase agreements	477	374	368
Federal Home Loan Bank advances	5,196	3,264	2,836
Subordinated debentures and term loans	7,572	7,185	6,661
Total Interest Expense	37,612	26,839	24,794
NET INTEREST INCOME	277,284	226,473	196,404
Provision for loan losses	9,143	5,657	417
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	268,141	220,816	195,987
OTHER INCOME
Service charges on deposit accounts	18,722	17,762	16,201
Fiduciary activities	11,589	9,818	9,196
Other customer fees	20,956	19,315	16,959
Commission income			4,147
Increase in cash surrender value of life insurance	3,906	3,630	2,919
Gains on life insurance benefits	2,671	643
Net gains and fees on sales of loans	7,564	7,052	6,483
Realized securities gains reclassified into income	2,631	3,389	2,670
Gain on sale of insurance subsidiary			8,265
Gain on cancellation of subordinated debentures			1,250
Other income	2,970	3,594	1,778
Total Other Income	71,009	65,203	69,868
OTHER EXPENSES
Salaries and employee benefits	119,812	102,552	101,908
Net occupancy	16,976	16,997	14,668
Equipment	13,090	12,497	10,787
Marketing	3,739	3,008	3,493
Outside data processing fees	12,242	9,148	7,109
Printing and office supplies	1,283	1,348	1,353
Intangible asset amortization	5,647	3,910	2,835
FDIC assessments	2,564	3,036	3,655
Other real estate owned and foreclosure expenses	1,903	2,877	3,956
Professional and other outside services	12,757	6,516	9,855
Other expenses	15,543	15,470	15,187
Total Other Expenses	205,556	177,359	174,806
INCOME BEFORE INCOME TAX	133,594	108,660	91,049
Income tax expense	37,524	27,609	25,665
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 96,070	$ 81,051	$ 65,384
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS PER SHARE DATA:
Basic (in dollars per share)	$ 2.13	$ 1.99	$ 1.73
Diluted (in dollars per share)	$ 2.12	$ 1.98	$ 1.72

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 96,070	$ 81,051	$ 65,384
Other comprehensive income (loss) net of tax:
Unrealized holding gain (loss) on securities available for sale arising during the period, net of tax of $5,193, $4,893, and $20	9,645	(9,087)	(37)
Unrealized gain (loss) on cash flow hedges arising during the period, net of tax of $4, $128, and $588	9	(240)	(1,093)
Reclassification adjustment for net gains included in net income net of tax of $576, $749, and $435	(1,070)	(1,390)	(808)
Defined benefit pension plans, net of tax of $1,125, $809, and $1,187
Net gain (loss) arising during period	2,686	(470)	2,404
Amortization of prior service cost	(597)	(1,032)	(198)
Period change	10,673	(12,219)	268
Comprehensive income	$ 106,743	$ 68,832	$ 65,652

CONSOLIDATED STATEMENTS OF COM6

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Unrealized holding gain (loss) on securities available for sale arising during the period, tax	$ 5,193	$ (4,893)	$ (20)
Unrealized gain (loss) on cash flow hedges arising during the period, tax	4	(128)	(588)
Reclassification adjustment for net losses (gains) included in net income, tax	576	749	435
Defined benefit pension plans, tax	$ (1,125)	$ 809	$ (1,187)

CONSOLIDATED STATEMENT OF STOCK

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2014		125	37,669,948
Beginning balance at Dec. 31, 2014	$ 726,827	$ 125	$ 4,709	$ 431,220	$ 292,403	$ (1,630)
Comprehensive income
Net income	65,384				65,384
Other comprehensive income (loss), net of tax	268					268
Cash dividends on common stock	(15,654)				(15,654)
Issuance of common stock related to acquisition (in shares)			2,769,568
Issuance of common stock related to acquisition	70,402		$ 346	70,056
Share-based compensation (in shares)			149,577
Share-based compensation	2,270		$ 19	2,251
Stock Issued under employee benefit plans (in shares)			22,074
Stock issued under employee benefit plans	460		$ 3	457
Stock issued under dividend reinvestment and stock purchase plan (in shares)			26,375
Stock issued under dividend reinvestment and stock purchase plan	661		$ 3	658
Stock options exercised (in shares)			96,066
Stock options exercised	1,531		$ 12	1,519
Stock redeemed (in shares)			(69,349)
Stock redeemed	(1,640)		$ (9)	(1,631)
Ending balance (in shares) at Dec. 31, 2015		125	40,664,259
Ending balance at Dec. 31, 2015	850,509	$ 125	$ 5,083	504,530	342,133	(1,362)
Comprehensive income
Net income	81,051				81,051
Other comprehensive income (loss), net of tax	(12,219)					(12,219)
Cash dividends on common stock	(22,203)				(22,203)
Issuance of common stock related to acquisition
Share-based compensation (in shares)			141,126
Share-based compensation	2,600		$ 17	2,583
Stock Issued under employee benefit plans (in shares)			20,545
Stock issued under employee benefit plans	462		$ 3	459
Stock issued under dividend reinvestment and stock purchase plan (in shares)			30,297
Stock issued under dividend reinvestment and stock purchase plan	835		$ 4	831
Stock options exercised (in shares)			128,848
Stock options exercised	2,602		$ 16	2,586
Stock redeemed (in shares)			(72,378)
Stock redeemed	(1,980)		$ (9)	(1,971)
Ending balance (in shares) at Dec. 31, 2016		125	40,912,697
Ending balance at Dec. 31, 2016	901,657	$ 125	$ 5,114	509,018	400,981	(13,581)
Comprehensive income
Net income	96,070				96,070
Other comprehensive income (loss), net of tax	10,673					10,673
Cash dividends on common stock	(31,820)				(31,820)
Issuance of common stock related to acquisition (in shares)			8,044,446
Issuance of common stock related to acquisition	321,431		$ 1,006	320,425
Share-based compensation (in shares)			89,362
Share-based compensation	2,827		$ 11	2,816
Stock Issued under employee benefit plans (in shares)			14,948
Stock issued under employee benefit plans	519		$ 2	517
Stock issued under dividend reinvestment and stock purchase plan (in shares)			24,058
Stock issued under dividend reinvestment and stock purchase plan	$ 991		$ 3	988
Stock options exercised (in shares)	104,748		104,748
Stock options exercised	$ 2,398		$ 13	2,385
Stock redeemed (in shares)			(32,021)
Stock redeemed	(1,283)		$ (4)	(1,279)
Ending balance (in shares) at Dec. 31, 2017		125	49,158,238
Ending balance at Dec. 31, 2017	$ 1,303,463	$ 125	$ 6,145	$ 834,870	$ 465,231	$ (2,908)

CONSOLIDATED STATEMENT OF STOC8

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends on common stock (in dollars per share)	$ 0.69	$ 0.54	$ 0.41

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flow From Operating Activities:
Net income	$ 96,070	$ 81,051	$ 65,384
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	9,143	5,657	417
Depreciation and amortization	7,967	7,161	6,262
Change in deferred taxes	15,523	8,611	4,444
Share-based compensation	2,827	2,600	2,270
Loans originated for sale	(377,252)	(354,265)	(364,411)
Proceeds from sales of loans held for sale	387,095	367,148	367,377
Gains on sales of loans held for sale	(5,910)	(5,918)	(5,625)
Gain on the sale of insurance subsidiary			8,265
Gain on cancellation of subordinated debentures			(1,250)
Gains on sales of securities available for sale	(2,631)	(3,389)	(2,670)
Increase in cash surrender of life insurance	(3,906)	(3,630)	(2,927)
Gains on life insurance benefits	(2,671)	(643)
Change in interest receivable	(6,838)	(1,779)	(2,833)
Change in interest payable	31	18	(162)
Other adjustments	7,054	1,097	(1,351)
Net cash provided by operating activities	126,502	103,719	56,660
Cash Flows from Investing Activities:
Net change in interest-bearing deposits	237,936	7,856	24,917
Purchases of:
Securities available for sale	(479,045)	(281,470)	(200,154)
Securities held to maturity	(30,220)	(110,797)	(87,282)
Proceeds from sales of securities available for sale	94,165	167,186	83,647
Proceeds from maturities of:
Securities available for sale	70,846	73,956	63,124
Securities held to maturity	72,220	119,052	98,581
Redemption (Purchase) of Federal Reserve and Federal Home Loan Bank stock	40	19,669	7,268
Net change in loans	(670,000)	(452,781)	(350,287)
Net cash and cash equivalents received (paid) in acquisition	54,536		(7,936)
Net cash received from sale of insurance subsidiary			15,155
Proceeds from the sale of other real estate owned	6,584	9,974	12,567
Proceeds from life insurance benefits	11,655	3,141
Other investing activities	(4,047)	(4,490)	9
Net cash used in investing activities	(635,330)	(448,704)	(340,391)
Net change in :
Demand and savings deposits	425,742	332,600	240,736
Certificates of deposit and other time deposits	75,236	(66,920)	(79,656)
Borrowings	1,088,189	1,107,795	491,660
Repayment of borrowings	(1,024,166)	(982,449)	(370,813)
Cash dividends on common stock	(31,820)	(22,203)	(15,654)
Stock issued under employee benefit plans	519	462	460
Stock issued under dividend reinvestment and stock purchase plans	991	835	661
Stock options exercised	2,398	2,602	1,531
Stock redeemed	(1,283)	(1,980)	(1,640)
Net cash provided by financing activities	535,806	370,742	267,285
Net Change in Cash and Cash Equivalents	26,978	25,757	(16,446)
Cash and Cash Equivalents, beginning of the year	127,927	102,170	118,616
Cash and Cash Equivalents, end of year	154,905	127,927	102,170
Additional cash flow information:
Interest paid	36,332	26,821	24,903
Income tax paid	22,421	11,999	21,200
Loans transferred to other real estate owned	8,360	1,684	3,644
Fixed assets transferred to other assets	6,753	360	1,600
Non-cash investing activities using trade date accounting	9,401	14,179	1,559
Liabilities assumed in conjunction with acquisitions
Fair value of assets acquired	1,531,397	0	635,047
Cash received (paid) in acquisition	(12)		(14,500)
Less: Common stock issued	321,431		70,402
Liabilities assumed	$ 1,209,954	$ 0	$ 550,145

Nature of Operations and Summar

Nature of Operations and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The accounting and reporting policies of the Corporation and the Bank, conform to accounting principles generally accepted in the United States of America and reporting practices followed by the banking industry. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The Corporation is a financial holding company whose principal activity is the ownership and management of the Bank and operates in a single significant business segment. The Bank provides full banking services under an Indiana state-charter. On April 1, 2016, the Board of Directors of the Bank adopted final resolutions approving the conversion of the Bank’s banking charter from a national association to an Indiana state-chartered bank. The initial application to convert was filed with the Indiana DFI on February 9, 2016. Between the date of initial application and adoption of the final resolutions by the Bank’s Board, the Indiana DFI and the FDIC conducted a joint exam of the Bank and its banking activities. Final regulatory approval of the application was obtained at the meeting of the Members of the Indiana DFI on April 14, 2016. The Bank filed official conversion documents effective April 15, 2016. As a result of the conversion, the Indiana DFI became the Bank’s primary regulator and the FDIC became the Bank’s primary federal regulator. Upon conversion, the Bank’s official name changed from “First Merchants Bank, National Association” to “First Merchants Bank.” The Bank continues operating under the following trade names in certain geographic markets: Lafayette Bank and Trust and First Merchants Private Wealth Advisors (each as a division of First Merchants Bank). The conversion did not affect the Bank’s operations or customers in any way, and Bank customers continued to receive identical protection on deposits through the FDIC’s deposit insurance program. The Bank generates commercial, mortgage, and consumer loans and receives deposits from customers located primarily in central and northern Indiana, northeast Illinois and central Ohio counties. The Bank’s loans are generally secured by specific items of collateral, including real property, consumer assets and business assets. A brief description of current accounting practices and current valuation methodologies are presented below. CONSOLIDATION of the Corporation's financial statements include the accounts of the Corporation and all its subsidiaries, after elimination of all material intercompany transactions. BUSINESS COMBINATIONS are accounted for under the acquisition method of accounting. Under the acquisition method, assets and liabilities of the business acquired are recorded at their estimated fair values as of the date of acquisition with any excess of the cost of the acquisition over the fair value of the net tangible and intangible assets acquired recorded as goodwill. Results of operations of the acquired business are included in the income statement from the date of acquisition. AVAILABLE FOR SALE SECURITIES are recorded at fair value on a recurring basis with the unrealized gains and losses, net of applicable income taxes, recorded in other comprehensive income. Realized gains and losses are recorded in earnings and the prior fair value adjustments are reclassified within stockholders' equity. Gains and losses on sales of securities are determined on the specific-identification method. Amortization of premiums and accretion of discounts are recorded as interest income from securities. Available for sale and held to maturity securities are evaluated for OTTI at least on a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. The investment securities portfolio is evaluated for OTTI by segregating the portfolio into two general segments and applying the appropriate OTTI model. Investment securities are generally evaluated for OTTI under ASC 320, Investments - Debt and Equity Securities . However, certain purchased beneficial interest, including certain non-agency government-sponsored mortgage-backed securities, asset-backed securities and collateralized debt obligations are evaluated using the model outlined in ASC 325-10, Investments - Other . In determining OTTI under ASC 320, management considers many factors, including: (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near term prospects of the issuer, (3) whether the market decline was affected by macroeconomic conditions, and (4) whether the Corporation has the intent to sell the debt security or more likely than not, will be required to sell the debt security before its anticipated recovery. The assessment of whether an other-than-temporary decline exists involves a high degree of subjectivity and judgment and is based on the information available to management at a point in time. When OTTI occurs, the amount of OTTI recognized in the income statement depends on whether the Corporation intends to sell the security or it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis, less any recognized credit loss. If the intent is to sell, or it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis, less any recognized credit loss, the OTTI shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis, less any recognized credit loss, and its fair value at the balance sheet date. If the intent is not to sell the security and it is not more likely than not that the Corporation will be required to sell the security before the recovery of its amortized cost basis less any recognized credit loss, the OTTI has been separated into the amount representing the credit loss and the amount related to all other factors. The amount of the total OTTI related to the credit loss is determined based on the present value of cash flows expected to be collected and is recognized in earnings. The amount of the total OTTI related to other factors is recognized in other comprehensive income, net of applicable income taxes. The previous amortized cost basis less the OTTI recognized in earnings becomes the new amortized cost basis of the investment. HELD TO MATURITY SECURITIES are classified as held to maturity when the Corporation has the positive intent and ability to hold the securities to maturity. Securities held to maturity are carried at amortized cost. For held to maturity debt securities, the amount of an OTTI recorded in other comprehensive income for the noncredit portion of a previous other-than-temporary impairment is amortized prospectively over the remaining life of the security on the basis of the timing of future estimated cash flows of the security. LOANS HELD FOR SALE are carried at the principal amount outstanding. The carrying amount approximates fair value due to the short duration between origination and the date of sale. LOANS held in the Corporation’s portfolio are carried at the principal amount outstanding, net of unearned income. Certain non-accrual, substantially delinquent and renegotiated loans classified as troubled debt restructures may be considered to be impaired in accordance with ASC 310, Receivables . Under ASC 310, a loan is impaired when, based on current information or events, it is probable that the Bank will be unable to collect all amounts due (principal and interest) according to the contractual terms of the loan agreement. Renegotiated consumer loans classified as troubled debt restructures are considered to be impaired. In applying the provisions of ASC 310, the Corporation considers all other investments in one-to-four family residential loans and consumer installment loans to be homogeneous and therefore excluded from separate identification for evaluation of impairment. Interest income is accrued on the principal balances of loans. The accrual of interest is discontinued on a loan when, in management’s opinion, the borrower may be unable to meet payments as they become due. When the interest accrual is discontinued, all unpaid accrued interest is reversed against earnings when considered uncollectible. Interest income accrued in the prior year, if any, is charged to the allowance for loan losses. Interest income is subsequently recognized only to the extent cash payments are received and the loan is returned to accruing status. Certain loan fees and direct costs are being deferred and amortized as an adjustment of yield on the loans. Impaired loans are carried at the fair value of collateral if the loan is collateral dependent, or the present value of estimated future cash flows using the loan’s existing rate. A portion of the allowance for loan losses is allocated to impaired loans if the value of such loans is deemed to be less than the unpaid balance. If these allocations cause the allowance for loan losses to increase, such increase is reported as a component of the provision for loan losses. Loan losses are charged against the allowance when management believes the uncollectability of the loan is confirmed. The valuation would be considered Level 3, consisting of appraisals of underlying collateral and discounted cash flow analysis. Loan commitments and letters-of-credit generally have short-term, variable-rate features and contain clauses which limit the Bank’s exposure to changes in customer credit quality. Accordingly, their carrying values, which are immaterial at the respective balance sheet dates, are reasonable estimates of fair value. LOANS ACQUIRED IN BUSINESS COMBINATIONS with evidence of credit deterioration since origination and for which it is probable that all contractually required payments will not be collected are considered to be purchased credit impaired. Evidence of credit quality deterioration as of purchase dates may include information such as past-due and nonaccrual status, borrower credit scores and recent loan to value percentages. Acquired credit-impaired loans are accounted for under the accounting guidance for loans and debt securities acquired with deteriorated credit quality (ASC 310-30). These loans are initially measured at fair value based upon expected cash flows without anticipation of prepayments and includes estimated future credit losses expected to be incurred over the life of the loans. As a result, related discounts are recognized subsequently through accretion based on the expected cash flows of the acquired loans. For purposes of applying ASC 310-30, loans acquired in business combinations are individually evaluated for the initial fair value measurement. Accordingly, allowances for credit losses related to these loans are not carried over and recorded at the acquisition date. The difference between contractually required payments and the cash flows expected to be collected at acquisition is referred to as the nonaccretable portion of the fair value discount or premium. The accretable portion of the fair value discount or premium is the difference between the expected cash flows and the net present value of expected cash flows, with such difference accreted into earnings over the term of the loans. Acquired loans not accounted for under ASC 310-30 are accounted for under ASC 310-20, which allows the fair value adjustment to be accreted into income over the remaining life of the loans. ALLOWANCE FOR LOAN LOSSES is maintained to absorb losses inherent in the loan portfolio and is based on ongoing, quarterly assessments of the probable losses inherent in the loan portfolio. The allowance is increased by the provision for loan losses, which is charged against current operating results. Loan losses are charged against the allowance when management believes the uncollectability of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The Corporation’s strategy for credit risk management includes credit policies and underwriting criteria for all loans, as well as an overall credit limit for each customer significantly below legal lending limits. The strategy also emphasizes diversification on regional geographic and industry levels, regular credit quality reviews and management reviews of large credit exposures and loans experiencing deterioration of credit quality. The Corporation’s methodology for assessing the appropriateness of the allowance consists of three key elements – the determination of the appropriate reserves for impaired loans accounted for under ASC 310, probable losses estimated from historical loss rates, and probable losses resulting from economic, environmental, qualitative or other deterioration above and beyond what is reflected in the first two components of the allowance. Commercial relationships greater than $500,000 that exhibit probable or observed credit weaknesses are subject to individual review. Where appropriate, reserves are allocated to individual loans based on management’s estimate of the borrower’s ability to repay the loan given the availability of collateral, other sources of cash flow and legal options available to the Corporation. Included in the review of individual loans are those that are impaired as provided in ASC 310. Any allowances for impaired loans are measured based on the fair value of the underlying collateral if collateral dependent or the present value of expected future cash flows discounted at the loan’s effective interest rate. The Corporation evaluates the collectability of principal when assessing the need for a loss accrual. Historical loss rates are applied to other commercial loans not subject to specific reserve allocations. The historical allocation for commercial loans graded pass are established by loan segments using loss rates based on the Corporation’s migration analysis. This migration analysis shows the loss rates for each segment of loans based on the loan grades at the beginning of the twelve month period. This loss rate is then applied to the current portfolio of loans in each respective loan segment. Homogenous loans, such as consumer installment and residential mortgage loans, are not individually risk graded. Reserves are established for each segment of loans using loss rates based on charge-offs for the same period as the migration analysis used for commercial loans. Historical loss allocations for commercial and consumer loans may be adjusted for significant factors that, in management’s judgment, reflect the impact of any current conditions on loss recognition. Factors which management considers in the analysis include the effects of the national and local economies, trends in loan growth and charge-off rates, changes in mix, concentration of loans in specific industries, asset quality trends (delinquencies, charge-offs and non-accrual loans), risk management and loan administration, changes in the internal lending policies and credit standards, examination results from bank regulatory agencies and the Corporation’s internal loan review. PENSION benefits are provided to the Corporation’s employees. Its accounting policies related to pensions and other post retirement benefits reflect the guidance in ASC 715, Compensation – Retirement Benefits. The Corporation does not consolidate the assets and liabilities associated with the pension plan. Instead, the Corporation recognizes the funded status of the plan in the consolidated balance sheets. The measurement of the funded status and the annual pension expense involves actuarial and economic assumptions. Various statistical and other factors, which attempt to anticipate future events, are used in calculating the expense and liabilities related to the plans. Key factors include assumptions on the expected rates of return on plan assets, discount rates, expected rates of salary increases and health care costs and trends. The Corporation considers market conditions, including changes in investment returns and interest rates in making these assumptions. The primary assumptions used in determining the Corporation’s pension and post retirement benefit obligations and related expenses are presented in NOTE 20. PENSION AND OTHER POST RETIREMENT BENEFIT PLANS of these Notes to Consolidated Financial Statements. PREMISES AND EQUIPMENT is carried at cost net of accumulated depreciation. Depreciation is computed using the straight-line and declining balance methods based on the estimated useful lives of the assets ranging from three to forty years. Maintenance and repairs are expensed as incurred, while major additions and improvements, which extend the useful life, are capitalized. Gains and losses on dispositions are included in current operations. FEDERAL HOME LOAN BANK STOCK is a required investment for institutions that are members of the FHLB. The Bank is a member of the FHLB of Indianapolis. Members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income. INTANGIBLE ASSETS that are subject to amortization, including core deposit intangibles, are being amortized on both the straight-line and accelerated basis over two to twenty years. Intangible assets are periodically evaluated as to the recoverability of their carrying value. GOODWILL is maintained by applying the provisions of ASC 350, Intangibles – Goodwill and Other . For purchase acquisitions, the Corporation is required to record the assets acquired, including identified intangible assets, and the liabilities assumed at their fair value, which in many instances involves estimates based on third party valuations, such as appraisals, or internal valuations based on discounted cash flow analysis or other valuation techniques that may include estimates of attrition, inflation, asset growth rates or other relevant factors. In addition, the determination of the useful lives for which an intangible asset will be amortized is subjective. Under ASC 350, the Corporation is required to evaluate goodwill for impairment on an annual basis, as well as on an interim basis, if events or changes indicate that the asset may be impaired, indicating that the carrying value may not be recoverable. The Corporation has historically elected to test for goodwill impairment as of October 1 of each year and has determined that no impairment exists. BANK OWNED LIFE INSURANCE has been purchased on certain employees and directors of the Corporation. The Corporation records the life insurance at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or amounts due that are probable at settlement. OTHER REAL ESTATE OWNED consists of assets acquired through, or in lieu of, loan foreclosure and are held for sale. They are initially recorded at fair value less cost to sell at the date of foreclosure, establishing a new cost basis. Subsequent to foreclosure, valuations are periodically performed by management and the assets are carried at the lower of carrying amount or fair value less cost to sell. Revenue and expenses from operations and changes in the valuation are included in other real estate owned and foreclosure expenses. Other real estate owned also includes bank premises formerly, but no longer used for banking. Bank premises are transferred at the lower of carrying value or fair value less cost to sell. DERIVATIVE INSTRUMENTS are carried at the fair value of the derivatives and reflects the estimated amounts that would have been received to terminate these contracts at the reporting date based upon pricing or valuation models applied to current market information. As part of the asset/liability management program, the Corporation will utilize, from time to time, interest rate floors, caps or swaps to reduce its sensitivity to interest rate fluctuations. These are derivative instruments, which are recorded as assets or liabilities in the consolidated balance sheets at fair value. Changes in the fair values of derivatives are reported in the consolidated statements of operations or AOCI depending on the use of the derivative and whether the instrument qualifies for hedge accounting. The key criterion for the hedge accounting is that the hedged relationship must be highly effective in achieving offsetting changes in those cash flows that are attributable to the hedged risk, both at inception of the hedge and on an ongoing basis. Derivatives that qualify for the hedge accounting treatment are designated as either: a hedge of the fair value of the recognized asset or liability or of an unrecognized firm commitment (a fair value hedge) or a hedge of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (a cash flow hedge). To date, the Corporation has only entered into a cash flow hedge. For cash flow hedges, changes in the fair values of the derivative instruments are reported in AOCI to the extent the hedge is effective. The gains and losses on derivative instruments that are reported in AOCI are reflected in the consolidated statements of income in the periods in which the results of operations are impacted by the variability of the cash flows of the hedged item. Generally, net interest income is increased or decreased by amounts receivable or payable with respect to the derivatives, which qualify for hedge accounting. At inception of the hedge, the Corporation establishes the method it uses for assessing the effectiveness of the hedging derivative and the measurement approach for determining the ineffective aspect of the hedge. The ineffective portion of the hedge, if any, is recognized in the consolidated statements of income. The Corporation excludes the time value expiration of the hedge when measuring ineffectiveness. The Corporation offers interest rate derivative products (e.g. interest rate swaps) to certain of its high-quality commercial borrowers. This product allows customers to enter into an agreement with the Corporation to swap their variable rate loan to a fixed rate. These derivative products are designed to reduce, eliminate or modify the risk of changes in the borrower’s interest rate or market price risk. The extension of credit incurred through the execution of these derivative products is subject to the same approvals and rigorous underwriting standards as the related traditional credit product. The Corporation limits its risk exposure to these products by entering into a mirror-image, offsetting swap agreement with a separate, well-capitalized and rated counterparty previously approved by the Credit and Asset Liability Committee. By using these interest rate swap arrangements, the Corporation is also better insulated from the interest rate risk associated with underwriting fixed-rate loans. These derivative contracts are not designated against specific assets or liabilities under ASC 815, Derivatives and Hedging , and, therefore, do not qualify for hedge accounting. The derivatives are recorded on the balance sheet at fair value and changes in fair value of both the customer and the offsetting swap agreements are recorded (and essentially offset) in non-interest income. The fair value of the derivative instruments incorporates a consideration of credit risk (in accordance with ASC 820, Fair Value Measurements and Disclosures ), resulting in some volatility in earnings each period. INCOME TAX in the consolidated statements of income includes deferred income tax provisions or benefits for all significant temporary differences in recognizing income and expenses for financial reporting and income tax purposes. The Corporation files consolidated income tax returns with its subsidiaries. The Corporation is generally no longer subject to U.S. federal, state and local income tax examinations by tax authorities for tax years before 2014 . The Corporation adopted the provisions of the ASC 740, Income Taxes , which prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. ASC 740 also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. As a result of the implementation of ASC 740, the Corporation did not identify any uncertain tax positions that it believes should be recognized in the financial statements. The Corporation's policy is to recognize interest and penalties related to unrecognized tax benefits, if any, as a component of income tax expense. STOCK OPTION AND RESTRICTED STOCK AWARD PLANS are maintained by the Corporation. The compensation costs are recognized for stock options and restricted stock awards issued to employees and directors based on the fair value of these awards at the date of grant. A Black-Scholes model is utilized to estimate the fair value of stock options. The market price of the Corporation’s common stock at the date of grant is used for restricted stock awards. Compensation expense is recognized over the appropriate service period, which is generally two or three years. TRANSFERS OF FINANCIAL ASSETS are accounted for as sales, when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Corporation and put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets and (3) the Corporation does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity or the ability to unilaterally cause the holder to return specific assets. NET INCOME PER SHARE is computed by dividing net income available to common shareholders by the weighted-average number of shares of common stock outstanding. Diluted net income per share is computed by dividing net income available to common shareholders by the weighted-average number of shares of common stock outstanding, plus the dilutive effect of outstanding stock options and nonvested restricted stock. RECLASSIFICATIONS have been made to prior financial statements to conform to the current financial statement presentation. These reclassifications had no effect on net income.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS Independent Alliance Banks, Inc. On November 21, 2016, the Corporation purchased 495,112 shares, or 12.1 percent, of IAB's outstanding common stock from an IAB shareholder for $19.8 million , or $40.00 per share. On July 14, 2017, the Corporation acquired the remaining shares of IAB common stock. IAB, an Indiana Corporation, merged with and into the Corporation, whereupon the separate corporate existence of IAB ceased and the Corporation survived. Immediately following the merger, IAB's wholly-owned subsidiary, iAB Financial Bank, merged with and into the Bank, with the Bank continuing as the surviving bank. IAB was headquartered in Fort Wayne, Indiana and had 16 banking centers serving the Fort Wayne market. Pursuant to the merger agreement, each IAB shareholder received 1.653 shares of the Corporation's common stock for each outstanding share of IAB common stock held. The Corporation issued approximately 6.0 million shares of common stock. The transaction value for the remaining shares of common stock, not owned by the Corporation, was approximately $238.8 million , resulting in a total purchase price of $258.6 million . The Corporation engaged in this transaction with the expectation that it would be accretive to income and add a new market area with a demographic profile consistent with many of the current Indiana markets served by the Bank. Goodwill resulted from this transaction due to the expected synergies and economies of scale. In the third quarter of 2017, ASC 805-10 - Business Combinations, required the Corporation to remeasure the 12.1 percent equity interest in IAB's common stock and recognize the resulting gain or loss, if any, in earnings. The remeasurement was based upon the closing price of IAB's common stock immediately prior to the acquisition announcement, and prior to the Corporation obtaining control of IAB. The trading price of IAB's common stock subsequent to the acquisition announcement included a control or acquisition premium and was not indicative of the fair value of the Corporation's pre-existing equity interest immediately prior to the acquisition announcement. The fair value of the equity interest in IAB's common stock after the remeasurement was $19.8 million. The Corporation recorded a $50,000 loss in 2017 as a result of the remeasurement and the loss is reflected in the Corporation's Consolidated Statements of Income in the line titled "Net realized gains on sales of available for sale securities." Under the acquisition method of accounting, the total purchase price is allocated to net tangible and intangible assets based on their current estimated fair values on the date of the acquisition. Based on preliminary valuations of the fair value of tangible and intangible assets acquired and liabilities assumed, which are based on assumptions that are subject to change, the purchase price for the IAB acquisition is detailed in the following table. If prior to the end of the one-year measurement period for finalizing the purchase price allocation, information becomes available which would indicate adjustments are required to the purchase price allocation, such adjustments will be included in the purchase price allocation retrospectively. Fair Value Cash and cash equivalents $ 6,016 Interest-bearing time deposits 248,212 Investment securities 4,078 Loans held for sale 594 Loans 725,382 Premises and equipment 10,107 Federal Home Loan Bank stock 4,810 Interest receivable 3,445 Cash surrender value of life insurance 26,964 Other assets 11,780 Deposits (862,271 ) Securities sold under repurchase agreements (17,915 ) Federal Home Loan Bank Advances (47,575 ) Subordinated debentures (10,583 ) Interest payable (1,005 ) Other liabilities (14,472 ) Net tangible assets acquired 87,567 Other Intangible assets 17,403 Goodwill 153,636 Purchase price $ 258,606 Of the total purchase price, $17,403,000 has been allocated to other intangible assets. Approximately $13.6 million was allocated to a core deposit intangible, which will be amortized over its estimated life of 10 years. Approximately $3.8 million was allocated to a non-compete intangible, which will be amortized over its estimated life of 2 years. The remaining purchase price has been allocated to goodwill, which is not deductible for tax purposes. Acquired loan data for IAB can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 4,838 $ 14,131 $ 8,352 Acquired receivables not subject to ASC 310-30 $ 720,544 $ 864,613 $ 9,786 The Arlington Bank On May 19, 2017, the Corporation acquired 100 percent of Arlington Bank. Arlington Bank, an Ohio savings bank, merged with and into the Bank, with the Bank continuing as the surviving bank. Arlington Bank was headquartered in Columbus, Ohio and had 3 banking centers serving the Columbus, Ohio market. Pursuant to the merger agreement, each Arlington Bank shareholder received 2.7245 shares of the Corporation's common stock for each outstanding share of Arlington Bank common stock held. The Corporation issued approximately 2.1 million shares of common stock, which was valued at approximately $82.6 million. The Corporation engaged in this transaction with the expectation that it would be accretive to income and expand the existing footprint in Columbus, Ohio. Goodwill resulted from this transaction due to the expected synergies and economies of scale. Under the acquisition method of accounting, the total purchase price is allocated to net tangible and intangible assets based on their current estimated fair values on the date of the acquisition. Based on preliminary valuations of the fair value of tangible and intangible assets acquired and liabilities assumed, which are based on assumptions that are subject to change, the purchase price for the Arlington Bank acquisition is detailed in the following table. If prior to the end of the one-year measurement period for finalizing the purchase price allocation, information becomes available which would indicate adjustments are required to the purchase price allocation, such adjustments will be included in the purchase price allocation retrospectively. Fair Value Cash and cash equivalents $ 48,532 Interest-bearing time deposits 292 Loans held for sale 7,626 Loans 224,680 Premises and equipment 1,986 Federal Home Loan Bank stock 1,091 Interest receivable 653 Other assets 1,620 Deposits (252,783 ) Interest payable (244 ) Other liabilities (3,106 ) Net tangible assets acquired 30,347 Core deposit intangible 4,526 Goodwill 47,719 Purchase price $ 82,592 Of the total purchase price, $4,526,000 has been allocated to a core deposit intangible that will be amortized over its estimated life of 10 years. The remaining purchase price has been allocated to goodwill, which is not deductible for tax purposes. Acquired loan data for Arlington Bank can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 2,625 $ 6,183 $ 2,891 Acquired receivables not subject to ASC 310-30 $ 222,055 $ 308,857 $ 2,741 Pro Forma Financial Information The results of operations of Arlington Bank and IAB have been included in the Corporation's consolidated financial statements since the acquisition dates. The following schedule includes pro forma results for the year ended December 31, 2017 and 2016 , as if the Arlington Bank and IAB acquisitions occurred as of the beginning of the periods presented. 2017 2016 Total revenue (net interest income plus other income) $ 380,324 $ 353,732 Net income $ 95,009 $ 95,288 Net income available to common shareholders Earnings per share: Basic $ 1.94 $ 1.95 Diluted $ 1.93 $ 1.94 The pro forma information includes adjustments for interest income on loans, interest expense on deposits and borrowings, premises expense for the banking centers acquired and amortization of intangibles arising from the transaction and the related income tax effects. The pro forma information for the year ended December 31, 2017 includes operating revenue of $9.0 million and $21.4 million from Arlington Bank and IAB acquisitions since the date of acquisition, respectively. Additionally, $15.4 million, net of tax, of expenses directly attributable to the Arlington Bank and IAB acquisitions were included in the year ended December 31, 2017 pro forma information. The pro forma information for the year ended December 31, 2016 includes operating results from Arlington Bank and IAB as if the acquisitions occurred at the beginning of the year. The pro forma information is presented for information purposes only and is not indicative of the results of operations that actually would have been achieved had the acquisitions been consummated as of that time, nor is it intended to be a projection of future results.

Restriction on Cash and Due Fro

Restriction on Cash and Due From Banks	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Restriction on Cash and Due From Banks	RESTRICTION ON CASH AND DUE FROM BANKS The Corporation considers all liquid investments with original maturities of three months or less to be cash equivalents. As of December 31, 2017 , cash and cash equivalents is defined to include cash on hand, deposits in other institutions and federal funds sold. At December 31, 2017 , the Corporation’s interest-bearing cash accounts and noninterest-bearing transaction deposits held at other institutions exceeded the $250,000 federally insured limits by approximately $128,127,000 . Each correspondent bank’s financial performance and market rating are reviewed on a quarterly basis to ensure the Corporation has deposits only at institutions providing minimal risk for those exceeding the federally insured limits. Additionally, the Corporation had approximately $5,826,000 at the Federal Home Loan Bank and Federal Reserve Bank, which are government-sponsored entities not insured by the FDIC. The Corporation is required to maintain reserve funds in cash and/or on deposit with the Federal Reserve Bank. The reserve required at December 31, 2017 , was $14,522,000 .

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investment Securities	INVESTMENT SECURITIES The amortized cost, gross unrealized gains, gross unrealized losses and approximate market value of the Corporation's investment securities at the dates indicated were: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available for sale at December 31, 2017 State and municipal $ 510,852 $ 16,932 $ 1,091 $ 526,693 U.S. Government-sponsored mortgage-backed securities 473,325 964 3,423 470,866 Corporate obligations 31 31 Equity securities 2,357 2,357 Total available for sale 986,565 17,896 4,514 999,947 Held to maturity at December 31, 2017 U.S. Government-sponsored agency securities 22,618 435 22,183 State and municipal 235,594 6,295 244 241,645 U.S. Government-sponsored mortgage-backed securities 301,443 3,341 1,404 303,380 Foreign Investment 1,000 1,000 Total held to maturity 560,655 9,636 2,083 568,208 Total Investment Securities $ 1,547,220 $ 27,532 $ 6,597 $ 1,568,155 Available for sale at December 31, 2016 U.S. Government-sponsored agency securities $ 100 $ 100 State and municipal 360,779 $ 8,443 $ 5,564 363,658 U.S. Government-sponsored mortgage-backed securities 313,459 1,904 3,071 312,292 Corporate obligations 31 31 Equity securities 21,820 1,039 20,781 Total available for sale 696,189 10,347 9,674 696,862 Held to maturity at December 31, 2016 U.S. Government-sponsored agency securities 22,619 479 22,140 State and municipal 224,811 3,136 1,796 226,151 U.S. Government-sponsored mortgage-backed securities 360,213 4,956 1,527 363,642 Total held to maturity 607,643 8,092 3,802 611,933 Total Investment Securities $ 1,303,832 $ 18,439 $ 13,476 $ 1,308,795 Certain investments in debt securities are reported in the financial statements at amounts less than their historical cost. The historical cost of these investments totaled $452,644,000 and $523,773,000 at December 31, 2017 and 2016 , respectively. Total fair value of these investments was $446,047,000 and $510,297,000 , which was approximately 28.6 and 39.1 percent of the Corporation's available for sale and held to maturity investment portfolio at December 31, 2017 and 2016 , respectively. Except as discussed below, management believes the decline in fair value for these securities was temporary. Should the impairment of any of these securities become other-than-temporary, the cost basis of the investment will be reduced and the resulting loss recognized in net income during the period the OTTI is identified. The Corporation’s management has evaluated all securities with unrealized losses for OTTI as of December 31, 2017 . The evaluations are based on the nature of the securities, the extent and duration of the loss and the intent and ability of the Corporation to hold these securities either to maturity or through the expected recovery period. In determining the fair value of the investment securities portfolio, the Corporation utilizes a third party for portfolio accounting services, including market value input, for those securities classified as Level I and Level II in the fair value hierarchy. The Corporation has obtained an understanding of what inputs are being used by the vendor in pricing the portfolio and how the vendor classified these securities based upon these inputs. From these discussions, the Corporation’s management is comfortable that the classifications are proper. The Corporation has gained trust in the data for two reasons: (a) independent spot testing of the data is conducted by the Corporation through obtaining market quotes from various brokers on a periodic basis; and (b) actual gains or loss resulting from the sale of certain securities has proven the data to be accurate over time. Fair value of securities classified as Level 3 in the valuation hierarchy was determined using a discounted cash flow model that incorporated market estimates of interest rates and volatility in markets that have not been active. U.S. Government-Sponsored Mortgage-Backed Securities The unrealized losses on the Corporation's investment in mortgage-backed securities were a result of interest rate changes. The Corporation expects to recover the amortized cost basis over the term of the securities. Because the decline in market value is attributable to changes in interest rates and not credit quality, and because the Corporation does not intend to sell the investments and it is not more likely than not that the Corporation will be required to sell the investments before recovery of their amortized cost basis, which may be maturity, the Corporation does not consider those investments to be other-than-temporarily impaired at December 31, 2017 . As noted in the table above, the mortgage-backed securities portfolio contains unrealized losses of $3,423,000 on sixty-three securities and $1,404,000 on thirty-six securities in the available for sale and held to maturity portfolios, respectively. All these securities are issued by a government-sponsored entity. State and Municipal Securities and U.S. Government-Sponsored Agency Securities The unrealized losses on the Corporation's investments in securities of state and political subdivisions and U.S. Government-Sponsored Agency securities were caused by interest rate increases. The contractual terms of those investments do not permit the issuer to settle the securities at a price less than the amortized cost basis of the investments. Because the Corporation does not intend to sell the investments and it is not more likely than not that the Corporation will be required to sell the investments before recovery of their amortized cost basis, which may be maturity, the Corporation does not consider those investments to be other-than-temporarily impaired at December 31, 2017 . As noted in the table above, the state and political subdivision securities portfolio contains unrealized losses of $1,091,000 on forty-two securities and $244,000 on twenty-eight securities in the available for sale and held to maturity portfolios, respectively. The U.S. Government-Sponsored Agency securities portfolio contains no unrealized losses in the available for sale portfolio, and $435,000 on five securities in the held to maturity portfolio. The following table shows the Corporation’s gross unrealized losses and fair value, aggregated by investment category and length of time the individual securities have been in a continuous unrealized loss position at December 31, 2017 and 2016 : Less than 12 Months 12 Months or Longer Total Fair Gross Fair Gross Fair Gross Temporarily Impaired Available for Sale Securities at December 31, 2017 State and municipal $ 13,296 $ 198 $ 35,324 $ 893 $ 48,620 $ 1,091 U.S. Government-sponsored mortgage-backed securities 182,755 1,520 68,667 1,903 251,422 3,423 Total Temporarily Impaired Available for Sale Securities 196,051 1,718 103,991 2,796 300,042 4,514 Temporarily Impaired Held to Maturity Securities at December 31, 2017 U.S. Government-sponsored agency securities 9,988 131 12,196 304 22,184 435 State and municipal 2,430 36 15,805 208 18,235 244 U.S. Government-sponsored mortgage-backed securities 62,508 485 43,078 919 105,586 1,404 Total Temporarily Impaired Held to Maturity Securities 74,926 652 71,079 1,431 146,005 2,083 Total Temporarily Impaired Investment Securities $ 270,977 $ 2,370 $ 175,070 $ 4,227 $ 446,047 $ 6,597 Less than 12 Months 12 Months or Longer Total Fair Gross Fair Gross Fair Gross Temporarily Impaired Available for Sale Securities at December 31, 2016 State and municipal $ 126,593 $ 5,564 $ 126,593 $ 5,564 U.S. Government-sponsored mortgage-backed securities 185,544 3,071 185,544 3,071 Equity securities 18,765 1,039 18,765 1,039 Total Temporarily Impaired Available for Sale Securities 330,902 9,674 330,902 9,674 Temporarily Impaired Held to Maturity Securities at December 31, 2016 U.S. Government-sponsored agency securities 19,121 479 19,121 479 State and municipal 50,897 1,796 50,897 1,796 U.S. Government-sponsored mortgage-backed securities 109,377 1,527 109,377 1,527 Total Temporarily Impaired Held to Maturity Securities 179,395 3,802 179,395 3,802 Total Temporarily Impaired Investment Securities $ 510,297 $ 13,476 $ 510,297 $ 13,476 The amortized cost and fair value of securities available for sale and held to maturity at December 31, 2017 by contractual maturity are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Available for Sale Held to Maturity Amortized Cost Fair Value Amortized Cost Fair Value Maturity Distribution at December 31, 2017 Due in one year or less $ 425 $ 425 $ 12,015 $ 12,158 Due after one through five years 5,040 5,204 76,146 76,334 Due after five through ten years 74,921 78,806 54,441 55,679 Due after ten years 430,497 442,289 116,610 120,657 510,883 526,724 259,212 264,828 U.S. Government-sponsored mortgage-backed securities 473,325 470,866 301,443 303,380 Equity securities 2,357 2,357 Total Investment Securities $ 986,565 $ 999,947 $ 560,655 $ 568,208 Securities with a carrying value of approximately $475,999,000 , $572,896,000 and $637,358,000 were pledged at December 31, 2017 , 2016 and 2015 , respectively, to secure certain deposits and securities sold under repurchase agreements, and for other purposes as permitted or required by law. The book value of securities sold under agreements to repurchase amounted to $136,639,000 at December 31, 2017, and $145,936,000 at December 31, 2016. Gross gains of $2,681,000 , $3,389,000 and $2,770,000 were realized on sales of investment securities in 2017 , 2016 and 2015 , respectively. Gross losses of $50,000 and $100,000 were realized on sales of investment securities in 2017 and 2015 , respectively. There were no losses from the sales of investment securities in 2016 .

Loans and Allowance

Loans and Allowance	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans and Allowance	90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,487,221 $ 2,967 $ 30 $ 3,275 $ 6,272 $ 1,493,493 Agriculture production financing and other loans to farmers 120,720 10 1,027 1,037 121,757 Real estate loans: Construction 610,896 1,193 $ 65 65 1,323 612,219 Commercial and farmland 2,542,048 6,923 166 603 12,951 20,643 2,562,691 Residential 948,947 4,010 308 56 9,444 13,818 962,765 Home equity 510,362 1,372 184 175 1,928 3,659 514,021 Individuals' loans for household and other personal expenditures 85,744 298 834 25 34 1,191 86,935 Lease financing receivables, net of unearned income 2,527 2,527 Other commercial loans 394,791 394,791 Loans $ 6,703,256 $ 16,773 $ 1,522 $ 924 $ 28,724 $ 47,943 $ 6,751,199 December 31, 2016 Current 30-59 Days 60-89 Days Loans > 90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,192,079 $ 466 $ 162 $ 100 $ 1,839 $ 2,567 $ 1,194,646 Agriculture production financing and other loans to farmers 78,360 1,329 1,329 79,689 Real estate loans: Construction 415,975 2,655 73 2,728 418,703 Commercial and farmland 1,932,896 1,385 3,027 15,754 20,166 1,953,062 Residential 725,338 3,664 635 9 9,523 13,831 739,169 Home equity 415,969 850 246 3 1,457 2,556 418,525 Individuals' loans for household and other personal expenditures 76,929 470 57 23 550 77,479 Lease financing receivables, net of unearned income 311 311 Other commercial loans 258,061 258,061 Loans $ 5,095,918 $ 9,490 $ 4,127 $ 112 $ 29,998 $ 43,727 $ 5,139,645 On occasion, borrowers experience declines in income and cash flow. As a result, these borrowers seek to reduce contractual cash outlays including debt payments. Concurrently, in an effort to preserve and protect its earning assets, specifically troubled loans, the Corporation works to maintain its relationship with certain customers who are experiencing financial difficulty by contractually modifying the borrower's debt agreement with the Corporation. In certain loan restructuring situations, the Corporation may grant a concession to a debtor experiencing financial difficulty, resulting in a trouble debt restructuring. A concession is deemed to be granted when, as a result of the restructuring, the Corporation does not expect to collect all original amounts due, including interest accrued at the original contract rate. If the payment of principal at original maturity is primarily dependent on the value of collateral, the current value of the collateral is considered in determining whether the principal will be paid. The following tables summarize troubled debt restructures in the Corporation's loan portfolio that occurred during the periods ended December 31, 2017 and 2016 : December 31, 2017 Pre-Modification Post-Modification Number Commercial and industrial loans $ 599 $ 376 3 Agriculture production financing and other loans to farmers 387 387 3 Real estate loans: Commercial and farmland 1,022 1,156 8 Residential 788 862 15 Home equity 195 107 4 Individuals' loans for household and other personal expenditures 13 14 1 Total $ 3,004 $ 2,902 34 December 31, 2016 Pre-Modification Post-Modification Number Commercial and industrial loans $ 410 $ 410 4 Agriculture production financing and other loans to farmers 1,368 1,234 4 Real estate loans: Commercial and farmland 3,978 3,954 7 Residential 1,126 1,183 17 Home equity 266 244 4 Individuals' loans for household and other personal expenditures 17 10 1 Total $ 7,165 $ 7,035 37 The following tables summarize the recorded investment of troubled debt restructures as of December 31, 2017 and 2016 , by modification type, that occurred during the years indicated: December 31, 2017 Term Rate Combination Total Commercial and industrial loans $ 203 $ 166 $ 369 Agriculture production financing and other farm loans 387 387 Real estate loans: Commercial and farmland 705 $ 59 232 996 Residential 761 85 846 Home equity 105 105 Individuals' loans for household and other personal expenditures 14 14 Total $ 1,295 $ 939 $ 483 $ 2,717 December 31, 2016 Term Rate Combination Total Commercial and industrial loans $ 397 $ 397 Agriculture production financing and other loans to farmers $ 660 $ 12 672 Real estate loans: Commercial and farmland 297 3,456 3,753 Residential 238 928 1,166 Home equity 266 266 Individuals' loans for household and other personal expenditures 9 9 Total $ 1,195 $ 1,215 $ 3,853 $ 6,263 Loans secured by commercial and farmland real estate made up 40 percent of the post-modification balances of the troubled debt restructured loans that occurred during the twelve months ending December 31, 2017 . The following tables summarize troubled debt restructures that occurred during the twelve months ended December 31, 2017 and 2016 , that subsequently defaulted during the period indicated and remained in default at period end. For purposes of this schedule, a loan is considered in default if it is 30 or more days past due. Twelve Months Ended December 31, 2017 Number of Loans Recorded Balance Real estate loans: Commercial and farmland 1 $ 14 Residential 4 323 Total 5 $ 337 Twelve Months Ended December 31, 2016 Number of Loans Recorded Balance Commercial and industrial loans 3 $ 197 Agriculture production financing and other loans to farmers 1 661 Real estate loans: Commercial and farmland 1 343 Residential 1 $ 64 Total 6 $ 1,265 For potential consumer loan restructures, impairment evaluation occurs prior to modification. Any subsequent impairment is typically addressed through the charge-off process, or may be addressed through a specific reserve. Consumer troubled debt restructures are generally included in the general historical allowance for loan loss at the post modification balance. Consumer non-accrual and delinquent troubled debt restructures are also considered in the calculation of the non-accrual and delinquency trend environmental allowance allocation. Consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process totaled $2,302,000 and $1,530,000 at December 31, 2017 and 2016, respectively. Commercial troubled debt restructured loans risk graded special mention, substandard, doubtful and loss are individually evaluated for impairment under ASC 310. Any resulting specific reserves are included in the allowance for loan losses. Commercial 30 - 89 day delinquent troubled debt restructures are included in the calculation of the delinquency trend environmental allowance allocation. With the exception of the acquired loans excluded from the allowance for loan losses, all commercial non-impaired loans, including non-accrual and 90+ day delinquents, are included in the ASC 450 loss estimate." id="sjs-B4">LOANS AND ALLOWANCE The Corporation's primary lending focus is small business and middle market commercial, commercial real estate and residential real estate, which results in portfolio diversification. The following tables show the composition of the loan portfolio, the allowance for loan losses and credit quality characteristics by collateral classification, excluding loans held for sale. Loans held for sale at December 31, 2017 and 2016 , were $7,216,000 and $2,929,000 , respectively. The following table illustrates the composition of the Corporation’s loan portfolio by loan class for the years indicated: December 31, 2017 December 31, 2016 Commercial and industrial loans $ 1,493,493 $ 1,194,646 Agricultural production financing and other loans to farmers 121,757 79,689 Real estate loans: Construction 612,219 418,703 Commercial and farmland 2,562,691 1,953,062 Residential 962,765 739,169 Home equity 514,021 418,525 Individuals' loans for household and other personal expenditures 86,935 77,479 Lease financing receivables, net of unearned income 2,527 311 Other commercial loans 394,791 258,061 Loans 6,751,199 5,139,645 Allowance for loan losses (75,032 ) (66,037 ) Net Loans $ 6,676,167 $ 5,073,608 Allowance, Credit Quality and Loan Portfolio The Corporation maintains an allowance for loan losses to cover probable credit losses identified during its loan review process. Management believes that the allowance for loan losses is adequate to cover probable losses inherent in the loan portfolio at December 31, 2017 . The process for determining the adequacy of the allowance for loan losses is critical to the Corporation’s financial results. It requires management to make difficult, subjective and complex judgments to estimate the effect of uncertain matters. The allowance for loan losses considers current factors, including economic conditions and ongoing internal and external examinations, and will increase or decrease as deemed necessary to ensure it remains adequate. In addition, the allowance as a percentage of charge-offs and nonperforming loans will change at different points in time based on credit performance, portfolio mix and collateral values. The allowance for loan losses is maintained through the provision for loan losses, which is a charge against earnings. The allowance is increased by provision expense and decreased by charge-offs less recoveries. All charge-offs are approved by the Bank's senior credit officers and in accordance with established policies. The Bank charges off a loan when a determination is made that all or a portion of the loan is uncollectible. The amount provided for loan losses in a given period may be greater than or less than net loan losses experienced during the period, and is based on management’s judgment as to the appropriate level of the allowance for loan losses. The determination of the provision amount is based on management’s ongoing review and evaluation of the loan portfolio, including an internally administered loan "watch" list and independent loan reviews. The evaluation takes into consideration identified credit problems, the possibility of losses inherent in the loan portfolio that are not specifically identified and management’s judgment as to the impact of the current environment and economic conditions on the portfolio. The allowance consists of specific impairment reserves as required by ASC 310-10-35, a component for historical losses in accordance with ASC 450 and the consideration of current environmental factors in accordance with ASC 450. A loan is deemed impaired when, based on current information or events, it is probable that all amounts due of principal and interest according to the contractual terms of the loan agreement will not be collected. The historical loss allocation for loans not deemed impaired according to ASC 450 is the product of the volume of loans within the non-impaired criticized and non-criticized risk grade classifications, each segmented by call code, and the historical loss factor for each respective classification and call code segment. The historical loss factors are based upon actual loss experience within each risk and call code classification. The historical look back period for non-criticized loans looks to the most recent rolling-four-quarter average and aligns with the look back period for non-impaired criticized loans. Each of the rolling four quarter periods used to obtain the average, include all charge-offs for the previous twelve-month period, therefore the historical look back period includes seven quarters. The resulting allocation is reflective of current conditions. Criticized loans are grouped based on the risk grade assigned to the loan. Loans with a special mention grade are assigned a loss factor, and loans with a classified grade but not impaired are assigned a separate loss factor. The loss factor computation for this allocation includes a segmented historical loss migration analysis of risk grades to charge-off. In addition to the specific reserves and historical loss components of the allowance, consideration is given to various environmental factors to ensure that losses inherent in the portfolio are reflected in the allowance for loan losses. The environmental component adjusts the historical loss allocations for non-impaired loans to reflect relevant current conditions that, in management's opinion, have an impact on loss recognition. Environmental factors that management reviews in the analysis include: national and local economic trends and conditions; trends in growth in the loan portfolio and growth in higher risk areas; levels of, and trends in, delinquencies and non-accruals; experience and depth of lending management and staff; adequacy of, and adherence to, lending policies and procedures including those for underwriting; industry concentrations of credit; and adequacy of risk identification systems and controls through the internal loan review and internal audit processes. In conformance with ASC 805 and ASC 820, loans purchased after December 31, 2008 are recorded at the acquisition date fair value. Such loans are included in the allowance to the extent a specific impairment is identified that exceeds the fair value adjustment on an impaired loan or the historical loss and environmental factor analysis indicates losses inherent in a purchased portfolio exceeds the fair value adjustment on the portion of the purchased portfolio not deemed impaired. At December 31, 2017, the allowance for loan losses was $75,032,000 , an increase of $8,995,000 from the December 31, 2016 balance of $66,037,000 . Net charge-offs for the twelve months ended December 31, 2017, were $148,000 , a decrease of $1,925,000 from the same period in 2016. The provision for loan losses for the twelve months ended December 31, 2017 was $9,143,000 , an increase of $3,486,000 from the same period in 2016. The determination of the provision for loan losses in any period is based on management’s continuing review and evaluation of the loan portfolio, and its judgment as to the impact of current economic conditions on the portfolio. The following tables summarize changes in the allowance for loan losses by loan segment for the twelve months ended December 31, 2017, 2016, and 2015: Twelve Months Ended December 31, 2017 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2016 $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Provision for losses 2,515 3,159 1,078 2,391 9,143 Recoveries on loans 1,590 2,260 324 706 4,880 Loans charged off (1,383 ) (1,737 ) (593 ) (1,315 ) (5,028 ) Balances, December 31, 2017 $ 30,418 $ 27,343 $ 3,732 $ 13,537 $ 2 $ 75,032 Twelve Months Ended December 31, 2016 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2015 $ 26,478 $ 22,145 $ 2,689 $ 11,139 $ 2 $ 62,453 Provision for losses 1,876 1,834 432 1,515 5,657 Recoveries on loans 1,806 2,090 369 1,091 5,356 Loans charged off (2,464 ) (2,408 ) (567 ) (1,990 ) (7,429 ) Balances, December 31, 2016 $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Twelve Months Ended December 31, 2015 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2014 $ 28,824 $ 19,327 $ 2,658 $ 13,152 $ 3 $ 63,964 Provision for losses (1,901 ) 1,710 299 310 $ (1 ) 417 Recoveries on loans 1,911 2,545 352 1,536 6,344 Loans charged off (2,356 ) (1,437 ) (620 ) (3,859 ) (8,272 ) Balances, December 31, 2015 $ 26,478 $ 22,145 $ 2,689 $ 11,139 $ 2 $ 62,453 The following tables show the Corporation’s allowance for loan losses and loan portfolio by loan segment for the years indicated: December 31, 2017 Commercial Commercial Consumer Residential Finance Total Allowance balances: Individually evaluated for impairment $ 666 $ 567 $ 404 $ 1,637 Collectively evaluated for impairment 29,752 26,776 $ 3,732 13,133 $ 2 73,395 Total Allowance for Loan Losses $ 30,418 $ 27,343 $ 3,732 $ 13,537 $ 2 $ 75,032 Loan balances: Individually evaluated for impairment $ 4,776 $ 21,009 $ 5 $ 3,941 $ 29,731 Collectively evaluated for impairment 2,003,844 3,131,589 86,930 1,471,309 $ 2,527 6,696,199 Loans acquired with deteriorated credit quality 1,421 22,312 1,536 25,269 Loans $ 2,010,041 $ 3,174,910 $ 86,935 $ 1,476,786 $ 2,527 $ 6,751,199 December 31, 2016 Commercial Commercial Consumer Residential Finance Total Allowance balances: Individually evaluated for impairment $ 37 $ 553 $ 298 $ 888 Collectively evaluated for impairment 27,659 23,108 $ 2,923 11,457 $ 2 65,149 Total Allowance for Loan Losses $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Loan balances: Individually evaluated for impairment $ 4,762 $ 21,358 $ 9 $ 4,450 $ 30,579 Collectively evaluated for impairment 1,520,981 2,315,686 77,470 1,151,396 $ 311 5,065,844 Loans acquired with deteriorated credit quality 6,653 34,721 1,848 43,222 Loans $ 1,532,396 $ 2,371,765 $ 77,479 $ 1,157,694 $ 311 $ 5,139,645 The risk characteristics of the Corporation’s material portfolio segments are as follows: Commercial Commercial lending is primarily based on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. The cash flows of borrowers, however, may not be as expected and the collateral securing these loans may fluctuate in value. Most commercial loans are secured by the tangible assets being financed such as equipment or real estate or other business assets such as accounts receivable or inventory and may incorporate a personal guarantee. Other loans may be unsecured, secured but under-collateralized or otherwise made on the basis of the enterprise value of an organization. In the case of loans secured by accounts receivable, the availability of funds for the repayment of these loans may be substantially dependent on the ability of the borrower to collect amounts due from its customers. Commercial real estate These loans are viewed primarily as cash flow loans and secondarily as loans secured by real estate. Commercial real estate lending typically involves higher loan principal amounts and the repayment of these loans is generally dependent on the successful operation of the property securing the loan or the business conducted on the property securing the loan. Commercial real estate loans may be more adversely affected by conditions in the real estate markets or in the general economy. Management monitors and evaluates commercial real estate loans based on collateral and risk grade criteria. In addition, management tracks the level of owner-occupied commercial real estate loans versus non-owner occupied loans. Consumer and Residential With respect to residential loans that are secured by 1-4 family residences and are typically owner occupied, the Corporation generally establishes a maximum loan-to-value ratio and requires private mortgage insurance if that ratio is exceeded. Home equity loans are secured by a subordinate interest in 1-4 family residences, and consumer loans are secured by consumer assets such as automobiles or recreational vehicles. Some consumer loans are unsecured such as small installment loans and certain lines of credit. Repayment of these loans is primarily dependent on the personal income and credit rating of the borrowers, which can be impacted by economic conditions in their market areas such as unemployment levels. Repayment on loans secured by 1-4 family residences can be impacted by changes in property values. Risk is mitigated by the fact that the loans are of smaller individual amounts and spread over a large number of borrowers. Loans are reclassified to a non-accruing status when, in management’s judgment, the collateral value and financial condition of the borrower do not justify accruing interest. When the interest accrual is discontinued, all unpaid accrued interest is reversed against earnings when considered uncollectible. Payments subsequently received on non-accrual loans are applied to principal. A loan is returned to accrual status when principal and interest are no longer past due and collectability is probable, typically after a minimum of six consecutive months of performance. Payments received on impaired accruing or delinquent loans are applied to interest income as accrued. The following table summarizes the Corporation’s non-accrual loans by loan class for the years indicated: December 31, 2017 December 31, 2016 Commercial and industrial loans $ 3,275 $ 1,839 Agriculture production financing and other loans to farmers 1,027 1,329 Real estate loans: Construction 65 73 Commercial and farmland 12,951 15,754 Residential 9,444 9,523 Home equity 1,928 1,457 Individuals' loans for household and other personal expenditures 34 23 Total $ 28,724 $ 29,998 Commercial impaired loans include non-accrual loans, loans accounted for under ASC 310-30, and loans risk graded as substandard, doubtful and loss that were still accruing but deemed impaired according to the guidance set forth in ASC 310. Also included in impaired loans are accruing loans that are contractually past due 90 days or more and troubled debt restructures. Allowable methods for determining the amount of impairment include estimating fair value using the fair value of the collateral for collateral dependent loans. If the impaired loan is identified as collateral dependent, then the fair value method for measuring the amount of impairment is utilized. This method requires obtaining a current independent appraisal of the collateral and applying a discount factor, which includes selling costs if applicable, to the value. The fair value of real estate is generally based on appraisals by qualified licensed appraisers. The appraisers typically determine the value of the real estate by utilizing an income or market valuation approach. If an appraisal is not available, the fair value may be determined by using a cash flow analysis. Fair value on other collateral such as business assets is typically ascertained by assessing, either singularly or some combination of, asset appraisals, accounts receivable aging reports, inventory listings and or customer financial statements. Both appraised values and values based on borrower’s financial information are discounted as considered appropriate based on age and quality of the information and current market conditions. The following tables show the composition of the Corporation’s commercial impaired loans, related allowance and interest income recognized while impaired by loan class for the years indicated: December 31, 2017 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 14,110 $ 3,850 $ 7,653 $ 186 Agriculture production financing and other loans to farmers 1,595 1,238 1,304 20 Real estate loans: Construction 2,530 1,396 1,420 64 Commercial and farmland 51,829 39,651 43,445 1,734 Residential 5,403 3,133 3,558 122 Home equity 80 40 48 Total $ 75,547 $ 49,308 $ 57,428 $ 2,126 Impaired loans with related allowance: Commercial and industrial loans $ 812 $ 782 $ 552 $ 1,517 Agriculture production financing and other loans to farmers 357 327 114 327 Real estate loans: Commercial and farmland 2,989 2,270 567 2,383 $ 4 Total $ 4,158 $ 3,379 $ 1,233 $ 4,227 $ 4 Total Impaired Loans $ 79,705 $ 52,687 $ 1,233 $ 61,655 $ 2,130 December 31, 2016 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 17,645 $ 10,074 $ 13,393 $ 499 Agriculture production financing and other loans to farmers 757 680 750 3 Real estate loans: Construction 5,946 3,178 3,255 258 Commercial and farmland 67,936 49,731 51,740 2,978 Residential 8,039 4,664 5,410 167 Home equity 82 44 44 Other commercial loans 11 Total $ 100,416 $ 68,371 $ 74,592 $ 3,905 Impaired loans with related allowance: Agriculture production financing and other loans to farmers $ 660 $ 660 $ 36 $ 691 Real estate loans: Commercial and farmland 4,238 2,985 553 2,989 Residential 65 34 23 38 Total $ 4,963 $ 3,679 $ 612 $ 3,718 Total Impaired Loans $ 105,379 $ 72,050 $ 612 $ 78,310 $ 3,905 December 31, 2015 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 22,151 $ 11,669 $ 12,578 $ 488 Agriculture production financing and other loans to farmers 370 361 439 Real estate loans: Construction 4,551 2,336 3,662 157 Commercial and farmland 95,930 69,024 71,569 3,328 Residential 11,262 7,338 7,926 244 Home equity 297 247 249 Other commercial loans 20 Total $ 134,581 $ 90,975 $ 96,423 $ 4,217 Impaired loans with related allowance: Commercial and industrial loans $ 3,043 $ 2,690 $ 1,247 $ 2,752 $ 38 Agriculture production financing and other loans to farmers 466 466 30 538 Real estate loans: Commercial and farmland 2,144 1,933 392 1,868 Residential 2,300 1,463 173 1,787 Total $ 7,953 $ 6,552 $ 1,842 $ 6,945 $ 38 Total Impaired Loans $ 142,534 $ 97,527 $ 1,842 $ 103,368 $ 4,255 As part of the ongoing monitoring of the credit quality of the Corporation's loan portfolio, management tracks certain credit quality indicators including trends related to: (i) the level of criticized commercial loans, (ii) net charge-offs, (iii) non-performing loans, (iv) covenant failures and (v) the general national and local economic conditions. The Corporation utilizes a risk grading of pass, special mention, substandard, doubtful and loss to assess the overall credit quality of large commercial loans. All large commercial credit grades are reviewed at a minimum of once a year for pass grade loans. Loans with grades below pass are reviewed more frequently depending on the grade. A description of the general characteristics of these grades is as follows: • Pass - Loans that are considered to be of acceptable credit quality. • Special Mention - Loans which possess some credit deficiency or potential weakness, which deserves close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the Corporation's credit position at some future date. Special mention assets are not adversely classified and do not expose the Corporation to sufficient risk to warrant adverse classification. The key distinctions of this category's classification are that it is indicative of an unwarranted level of risk; and weaknesses are considered “potential”, not “defined”, impairments to the primary source of repayment. Examples include businesses that may be suffering from inadequate management, loss of key personnel or significant customer or litigation. • Substandard - A substandard loan is inadequately protected by the current net worth and paying capacity of the obligor or of the collateral pledged, if any. Assets so classified have a well-defined weakness that jeopardizes the liquidation of the debt. They are characterized by the distinct possibility that the Corporation will sustain some loss if the deficiencies are not corrected. Other characteristics may include: o the likelihood that a loan will be paid from the primary source of repayment is uncertain or financial deterioration is underway and very close attention is warranted to ensure that the loan is collected without loss, o the primary source of repayment is gone, and the Corporation is forced to rely on a secondary source of repayment, such as collateral liquidation or guarantees, o loans have a distinct possibility that the Corporation will sustain some loss if deficiencies are not corrected, o unusual courses of action are needed to maintain a high probability of repayment, o the borrower is not generating enough cash flow to repay loan principal; however, it continues to make interest payments, o the Corporation is forced into a subordinated or unsecured position due to flaws in documentation, o loans have been restructured so that payment schedules, terms and collateral represent concessions to the borrower when compared to the normal loan terms, o the Corporation is seriously contemplating foreclosure or legal action due to the apparent deterioration of the loan, and o there is significant deterioration in market conditions to which the borrower is highly vulnerable. • Doubtful - Loans that have all of the weaknesses of those classified as Substandard. However, based on currently existing facts, conditions and values, these weaknesses make full collection of principal highly questionable and improbable. Other credit characteristics may include the primary source of repayment is gone or there is considerable doubt as to the quality of the secondary sources of repayment. The possibility of loss is high, but because of certain important pending factors that may strengthen the loan, loss classification is deferred until the exact status of repayment is known. • Loss – Loans that are considered uncollectible and of such little value that continuing to carry them as an asset is not warranted. Loans will be classified as Loss when it is neither practical or desirable to defer writing off or reserving all or a portion of a basically worthless asset, even though partial recovery may be possible at some time in the future. The following tables summarize the credit quality of the Corporation’s loan portfolio, by loan class for the years indicated. Consumer non-performing loans include accruing consumer loans 90 plus days delinquent and consumer non-accrual loans. The entire balance of a loan is considered delinquent if the minimum payment contractually required to be made is not received by the specified date. Loans that evidenced deterioration of credit quality since origination and it was probable, at acquisition, that all contractually required payments would not be collected are included in the applicable categories below. December 31, 2017 Commercial Pass Commercial Special Mention Commercial Substandard Commercial Doubtful Commercial Loss Consumer Performing Consumer Total Commercial and industrial loans $ 1,418,401 $ 51,336 $ 23,386 $ 370 $ 1,493,493 Agriculture production financing and other loans to farmers 73,800 27,502 20,018 387 $ 50 121,757 Real estate loans: Construction 587,906 828 981 $ 22,374 $ 130 612,219 Commercial and farmland 2,408,329 70,074 79,769 1,536 2,980 3 2,562,691 Residential 185,725 4,376 4,209 114 759,900 8,441 962,765 Home equity 28,554 457 286 482,661 2,063 514,021 Individuals' loans for household and other personal expenditures 86,875 60 86,935 Lease financing receivables, net of unearned income 2,527 2,527 Other commercial loans 394,222 569 394,791 Loans $ 5,099,464 $ 154,573 $ 129,218 $ 2,407 $ 50 $ 1,354,790 $ 10,697 $ 6,751,199 December 31, 2016 Commercial Pass Commercial Special Mention Commercial Substandard Commercial Doubtful Commercial Loss Consumer Performing Consumer Total Commercial and industrial loans $ 1,117,545 $ 30,919 $ 46,182 $ 1,194,646 Agriculture production financing and other loans to farmers 30,712 25,273 23,704 79,689 Real estate loans: Construction 398,646 3,490 1,858 $ 14,636 $ 73 418,703 Commercial and farmland 1,811,367 60,028 80,626 1,034 7 1,953,062 Residential 146,251 5,106 6,046 574,054 7,712 739,169 Home equity 7,310 47 516 409,237 1,415 418,525 Individuals' loans for household and other personal expenditures 77,456 23 77,479 Lease financing receivables, net of unearned income 228 83 311 Other commercial loans 257,861 200 258,061 Loans $ 3,769,920 $ 124,863 $ 159,215 $ 1,076,417 $ 9,230 $ 5,139,645 The tables below show a past due aging of the Corporation’s loan portfolio, by loan class, for the years indicated: December 31, 2017 Current 30-59 Days 60-89 Days Loans > 90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,487,221 $ 2,967 $ 30 $ 3,275 $ 6,272 $ 1,493,493 Agriculture production financing and other loans to farmers 120,720 10 1,027 1,037 121,757 Real estate loans: Construction 610,896 1,193 $ 65 65 1,323 612,219 Commercial and farmland 2,542,048 6,923 166 603 12,951 20,643 2,562,691 Residential 948,947 4,010 308 56 9,444 13,818 962,765 Home equity 510,362 1,372 184 175 1,928 3,659 514,021 Individuals' loans for household and other personal expenditures 85,744 298 834 25 34 1,191 86,935 Lease financing receivables, net of unearned income 2,527 2,527 Other commercial loans 394,791 394,791 Loans $ 6,703,256 $ 16,773 $ 1,522 $ 924 $ 28,724 $ 47,943 $ 6,751,199 December 31, 2016 Current 30-59 Days 60-89 Days Loans > 90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,192,079 $ 466 $ 162 $ 100 $ 1,839 $ 2,567 $ 1,194,646 Agriculture production financing and other loans to farmers 78,360 1,329 1,329 79,689 Real estate loans: Construction 415,975 2,655 73 2,728 418,703 Commercial and farmland 1,932,896 1,385 3,027 15,754 20,166 1,953,062 Residential 725,338 3,664 635 9 9,523 13,831 739,169 Home equity 415,969 850 246 3 1,457 2,556 418,525 Individuals' loans for household and other personal expenditures 76,929 470 57 23 550 77,479 Lease financing receivables, net of unearned income 311 311 Other commercial loans 258,061 258,061 Loans $ 5,095,918 $ 9,490 $ 4,127 $ 112 $ 29,998 $ 43,727 $ 5,139,645 On occasion, borrowers experience declines in income and cash flow. As a result, these borrowers seek to reduce contractual cash outlays including debt payments. Concurrently, in an effort to preserve and protect its earning assets, specifically troubled loans, the Corporation works to maintain its relationship with certain customers who are experiencing financial difficulty by contractually modifying the borrower's debt agreement with the Corporation. In certain loan restructuring situations, the Corporation may grant a concession to a debtor experiencing financial difficulty, resulting in a trouble debt restructuring. A concession is deemed to be granted when, as a result of the restructuring, the Corporation does not expect to collect all original amounts due, including interest accrued at the original contract rate. If the payment of principal at original maturity is primarily dependent on the value of collateral, the current value of the collateral is considered in determining whether the principal will be paid. The following tables summarize troubled debt restructures in the Corporation's loan portfolio that occurred during the periods ended December 31, 2017 and 2016 : December 31, 2017 Pre-Modification Post-Modification Number Commercial and industrial loans $ 599 $ 376 3 Agriculture production financing and other loans to farmers 387 387 3 Real estate loans: Commercial and farmland 1,022 1,156 8 Residential 788 862 15 Home equity 195 107 4 Individuals' loans for household and other personal expenditures 13 14 1 Total $ 3,004 $ 2,902 34 December 31, 2016 Pre-Modification Post-Modification Number Commercial and industrial loans $ 410 $ 410 4 Agriculture production financing and other loans to farmers 1,368 1,234 4 Real estate loans: Commercial and farmland 3,978 3,954 7 Residential 1,126 1,183 17 Home equity 266 244 4 Individuals' loans for household and other personal expenditures 17 10 1 Total $ 7,165 $ 7,035 37 The following tables summarize the recorded investment of troubled debt restructures as of December 31, 2017 and 2016 , by modification type, that occurred during the years indicated: December 31, 2017 Term Rate Combination Total Commercial and industrial loans $ 203 $ 166 $ 369 Agriculture production financing and other farm loans 387 387 Real estate loans: Commercial and farmland 705 $ 59 232 996 Residential 761 85 846 Home equity 105 105 Individuals' loans for household and other personal expenditures 14 14 Total $ 1,295 $ 939 $ 483 $ 2,717 December 31, 2016 Term Rate Combination Total Commercial and industrial loans $ 397 $ 397 Agriculture production financing and other loans to farmers $ 660 $ 12 672 Real estate loans: Commercial and farmland 297 3,456 3,753 Residential 238 928 1,166 Home equity 266 266 Individuals' loans for household and other personal expenditures 9 9 Total $ 1,195 $ 1,215 $ 3,853 $ 6,263 Loans secured by commercial and farmland real estate made up 40 percent of the post-modification balances of the troubled debt restructured loans that occurred during the twelve months ending December 31, 2017 . The following tables summarize troubled debt restructures that occurred during the twelve months ended December 31, 2017 and 2016 , that subsequently defaulted during the period indicated and remained in default at period end. For purposes of this schedule, a loan is considered in default if it is 30 or more days past due. Twelve Months Ended December 31, 2017 Number of Loans Recorded Balance Real estate loans: Commercial and farmland 1 $ 14 Residential 4 323 Total 5 $ 337 Twelve Months Ended December 31, 2016 Number of Loans Recorded Balance Commercial and industrial loans 3 $ 197 Agriculture production financing and other loans to farmers 1 661 Real estate loans: Commercial and farmland 1 343 Residential 1 $ 64 Total 6 $ 1,265 For potential consumer loan restructures, impairment evaluation occurs prior to modification. Any subsequent impairment is typically addressed through the charge-off process, or may be addressed through a specific reserve. Consumer troubled debt restructures are generally included in the general historical allowance for loan loss at the post modification balance. Consumer non-accrual and delinquent troubled debt restructures are also considered in the calculation of the non-accrual and delinquency trend environmental allowance allocation. Consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process totaled $2,302,000 and $1,530,000 at December 31, 2017 and 2016, respectively. Commercial troubled debt restructured loans risk graded special mention, substandard, doubtful and loss are individually evaluated for impairment under ASC 310. Any resulting specific reserves are included in the allowance for loan losses. Commercial 30 - 89 day delinquent troubled debt restructures are included in the calculation of the delinquency trend environmental allowance allocation. With the exception of the acquired loans excluded from the allowance for loan losses, all commercial non-impaired loans, including non-accrual and 90+ day delinquents, are included in the ASC 450 loss estimate.

Accounting for Certain Loans Ac

Accounting for Certain Loans Acquired in a Purchase	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Accounting for Certain Loans Acquired in a Purchase	ACCOUNTING FOR CERTAIN LOANS ACQUIRED IN A PURCHASE The acquired loans detailed in the tables below are included in NOTE 5. LOANS AND ALLOWANCE of these Notes to Consolidated Financial Statements. As described in NOTE 5, loans purchased after December 31, 2008 are recorded at the acquisition date fair value, which could result in a fair value discount or premium. Purchased loans with evidence of credit deterioration since origination and for which it is probable at the date of acquisition that the acquirer will not collect all contractually required principal and interest payments are accounted for under ASC 310-30, Loans Acquired with Deteriorated Credit Quality . The difference between contractually required payments and the cash flows expected to be collected at acquisition is referred to as the nonaccretable difference. The accretable portion of the fair value discount or premium is the difference between the expected cash flows and the net present value of expected cash flows, with such difference accreted into earnings over the term of the loans. All other loans not accounted for under ASC 310-30 are accounted for under ASC 310-20, which allows the fair value adjustment to be accreted into income over the remaining life of the loans. The Corporation's most recent acquisitions, Arlington Bank and IAB, are detailed in NOTE 2. ACQUISITIONS of these Notes to Consolidated Financial Statements. All of the Corporation's acquisitions since December 31, 2008 are as indicated below. The following tables include the outstanding balance and carrying amount of all acquired loans which were included in the Corporation's balance sheet at December 31, 2017 and December 31, 2016. December 31, 2017 IAB Arlington Bank Ameriana C Financial Community CFS SCB Total Outstanding Balance: Commercial and industrial loans $ 83,630 $ 3,152 $ 4,150 $ 64 $ 235 $ 10,539 $ 1,760 $ 103,530 Agricultural production financing and other loans to farmers 33,537 76 50 1,317 34,980 Real estate loans: Construction 23,571 14,716 2,451 830 1,499 65 43,132 Commercial and farmland 346,155 76,375 79,739 15,791 27,910 65,578 6,733 618,281 Residential 100,569 69,011 86,098 32,854 6,354 79,674 2,899 377,459 Home equity 36,349 22,581 8,800 5,733 4,392 19,972 9,636 107,463 Individuals' loans for household and other personal expenditures 3,552 174 356 82 22 21 4,207 Other commercial loans 11,189 90 1,745 58 13,082 Total 638,552 186,099 183,339 55,272 40,548 175,958 22,366 1,302,134 Remaining fair value discount (20,090 ) (5,242 ) (6,689 ) (1,266 ) (2,482 ) (5,859 ) (2,120 ) (43,748 ) Carrying amount 618,462 180,857 176,650 54,006 38,066 170,099 20,246 1,258,386 Allowance 290 411 52 16 769 Carrying amount net of allowance $ 618,172 $ 180,857 $ 176,239 $ 54,006 $ 38,014 $ 170,083 $ 20,246 $ 1,257,617 December 31, 2016 Ameriana C Financial Community CFS SCB Total Outstanding Balance: Commercial and industrial loans $ 8,003 $ 85 $ 2,269 $ 23,327 $ 3,552 $ 37,236 Agricultural production financing and other loans to farmers 1,030 50 1,630 2,710 Real estate loans: Construction 22,017 2,835 4,026 420 29,298 Commercial and farmland 103,075 22,130 36,947 131,895 9,315 303,362 Residential 103,414 44,101 9,363 96,627 4,135 257,640 Home Equity 11,728 7,947 6,326 26,894 11,924 64,819 Individuals' loans for household and other personal expenditures 762 2 147 201 30 1,142 Other commercial loans 1,825 65 1,890 Total 250,824 77,100 60,108 279,479 30,586 698,097 Remaining fair value discount (10,771 ) (1,906 ) (4,101 ) (12,634 ) (3,268 ) (32,680 ) Carrying Amount 240,053 75,194 56,007 266,845 27,318 665,417 Allowance 265 23 92 380 Carrying Amount Net of Allowance $ 239,788 $ 75,194 $ 55,984 $ 266,753 $ 27,318 $ 665,037 The outstanding balance and related carrying amount of loans acquired and accounted for under ASC 310-30 as of December 31, 2017 were $38.9 million and $25.3 million , respectively; with no required allowance for loan losses. Comparatively, the outstanding balance and related carrying amount as of December 31, 2016 were $60.5 million and $43.2 million , respectively; with no required allowance for loan losses. During the twelve months ended December 31, 2017, one loan with a December 31, 2016 outstanding balance of $12.1 million and a carrying amount of $7.6 million , was transferred to other real estate owned. As customer cash flow expectations improve on loans accounted for under ASC310-30, nonaccretable yield can be reclassified to accretable yield. The accretable portion, or income expected to be collected, and reclassifications from nonaccretable, are identified in the tables below for the years indicated. Twelve Months Ended December 31, 2017 IAB Arlington Bank Ameriana C Financial Community CFS SCB Total Beginning balance $ 1,629 $ 73 $ 1,233 $ 736 $ 279 $ 3,950 Additions $ 941 $ 667 1,608 Accretion (1,009 ) (314 ) (2,983 ) (260 ) (454 ) (1,172 ) (557 ) (6,749 ) Reclassification from nonaccretable 834 164 1,805 187 212 1,075 471 4,748 Disposals (122 ) (545 ) (667 ) Ending balance $ 766 $ 517 $ 451 $ 869 $ 94 $ 193 $ 2,890 Twelve Months Ended December 31, 2016 Ameriana C Financial Community CFS SCB Total Beginning balance $ 2,160 $ 114 $ 1,508 $ 1,188 $ 642 $ 5,612 Additions Accretion (311 ) (123 ) (1,119 ) (4,268 ) (756 ) (6,577 ) Reclassification from nonaccretable 12 82 858 3,827 393 5,172 Disposals (232 ) (14 ) (11 ) (257 ) Ending balance $ 1,629 $ 73 $ 1,233 $ 736 $ 279 $ 3,950 Twelve Months Ended December 31, 2015 Ameriana C Financial Community CFS SCB Total Beginning balance $ 2,122 $ 2,400 $ 868 $ 5,390 Additions $ 2,160 $ 145 2,305 Accretion (31 ) (723 ) (4,050 ) (1,046 ) (5,850 ) Reclassification from nonaccretable 249 2,854 822 3,925 Disposals (140 ) (16 ) (2 ) (158 ) Ending balance $ 2,160 $ 114 $ 1,508 $ 1,188 $ 642 $ 5,612 The following table presents loans acquired during the period ending December 31, 2017, for which it was probable at acquisition that all contractually required payments would not be collected. There were no loans acquired during the period ending December 31, 2016. 2017 IAB Arlington Bank Total Contractually required payments receivable at acquisition date $ 14,131 $ 6,183 $ 20,314 Nonaccretable difference 8,352 2,891 11,243 Expected cash flows at acquisition date 5,779 3,292 9,071 Accretable difference 941 667 1,608 Basis in loans at acquisition date $ 4,838 $ 2,625 $ 7,463

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT The following table summarizes the Corporation's premises and equipment as of December 31, 2017 and 2016 : 2017 2016 Cost at December 31: Land $ 22,042 $ 25,035 Buildings and Leasehold Improvements 124,441 114,444 Equipment 82,344 65,547 Total Cost 228,827 205,026 Accumulated Depreciation and Amortization (132,975 ) (110,594 ) Net $ 95,852 $ 94,432 The IAB acquisition on July 14, 2017 and the Arlington Bank acquisition on May 19, 2017 resulted in additions to premises and equipment of $10,107,000 and $1,986,000 , respectively. Details regarding the acquisitions are discussed in NOTE 2. ACQUISITIONS of these Notes to Consolidated Financial Statements. The Corporation is committed under various non-cancelable lease contracts for certain subsidiary office facilities and equipment. Total lease expense for 2017 , 2016 and 2015 was $4,072,000 , $4,586,000 and $3,456,000 , respectively. The future minimum rental commitments required under the operating leases, which expire at various dates through the year 2035, are as follows for the years ending December 31: Future Minimum Rental Commitments 2018 $ 3,161 2019 3,611 2020 3,484 2021 3,137 2022 3,090 After 2022 15,180 Total Future Minimum Obligations $ 31,663

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	GOODWILL Goodwill is recorded on the acquisition date of an entity. During the measurement period, the Corporation may record subsequent adjustments to goodwill for provisional amounts recorded at the acquisition date. The IAB acquisition on July, 14, 2017 resulted in $153,636,000 of goodwill. The Arlington Bank acquisition on May 19, 2017 resulted in $47,719,000 of goodwill, which includes a reduction of $469,000 . This reduction was recorded in the third quarter of 2017 as a measurement period adjustment. The Ameriana acquisition on December 31, 2015 resulted in $38,624,000 of goodwill, of which, $871,000 was recorded during the first quarter of 2016 as a measurement period adjustment. Details regarding the IAB and Arlington Bank acquisitions are discussed in NOTE 2. ACQUISITIONS of these Notes to Consolidated Financial Statements. No impairment loss was recorded in 2017 or 2016. The Corporation tested goodwill for impairment during 2017 and 2016. In both valuations, the fair value exceeded the Corporation’s carrying value; therefore, it was concluded goodwill is not impaired. For additional details related to impairment testing, see the “GOODWILL” section of Management’s Discussion and Analysis of Financial Condition and Results of Operations included as Item 7 of this Annual Report on Form 10-K. 2017 2016 Balance, January 1 $ 244,000 $ 243,129 Goodwill acquired 201,824 Measurement period adjustment (469 ) $ 871 Balance, December 31 $ 445,355 $ 244,000

Other Intangibles

Other Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangibles	OTHER INTANGIBLES Core deposit intangibles and other intangibles are recorded on the acquisition date of an entity. During the measurement period, the Corporation may record subsequent adjustments to these intangibles for provisional amounts recorded at the acquisition date. The IAB acquisition on July 14, 2017 resulted in a core deposit intangible of $13,638,000 and other intangibles, consisting of non-compete intangibles, of $3,765,000 . The Arlington Bank acquisition on May 19, 2017 resulted in a core deposit intangible of $4,526,000 . The Ameriana acquisition on December 31, 2015 resulted in a core deposit intangible of $5,342,000 , of which, $2,142,000 was recorded as a measurement period adjustment in the first quarter of 2016. Details regarding the IAB and Arlington Bank acquisitions are discussed in NOTE 2. ACQUISITIONS of these in the Notes to Consolidated Financial Statements. The carrying basis and accumulated amortization of recognized core deposit and other intangibles are noted below. 2017 2016 Gross carrying amount $ 63,940 $ 61,798 Core deposit intangible acquired 18,164 Other intangibles acquired 3,765 Measurement period adjustment 2,142 Accumulated amortization (54,721 ) (49,074 ) Core deposit intangible and other intangibles reduction Core Deposit and Other Intangibles $ 31,148 $ 14,866 Amortization expense for the years ended December 31, 2017 , 2016 and 2015 , was $5,647,000 , $3,910,000 and $2,835,000 , respectively. Estimated future amortization expense is summarized as follows: Amortization Expense 2018 $ 6,719 2019 5,169 2020 3,632 2021 3,427 2022 3,325 After 2022 8,876 $ 31,148

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Deposits	DEPOSITS The composition of the deposit portfolio is included in the table below for the years indicated: December 31, 2017 December 31, 2016 Demand deposits $ 3,746,654 $ 2,866,853 Savings deposits 1,994,366 1,560,752 Certificates and other time deposits of $100,000 or more 468,895 276,274 Other certificates and time deposits 581,894 471,247 Brokered deposits 380,721 381,372 Total deposits $ 7,172,530 $ 5,556,498 At December 31, 2017 and 2016 , deposits exceeding the FDIC's Standard Maximum Deposit Insurance Amount of $250,000 were $3.2 billion and $2.2 billion , respectively. At December 31, 2017 , the contractual maturities of time deposits are summarized as follows: Certificates and Other Time Deposits 2018 $ 876,126 2019 330,892 2020 119,066 2021 63,005 2022 27,518 After 2022 14,903 $ 1,431,510

Transfers Accounted for as Secu

Transfers Accounted for as Secured Borrowings	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Transfers Accounted for as Secured Borrowings	TRANSFERS ACCOUNTED FOR AS SECURED BORROWINGS The collateral pledged for all repurchase agreements that are accounted for as secured borrowings as of December 31, 2017 and 2016 were: December 31, 2017 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater Than 90 Days Total U.S. Government-sponsored mortgage-backed securities $ 126,187 1,340 1,500 $ 7,596 $ 136,623 December 31, 2016 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater Than 90 Days Total U.S. Government-sponsored mortgage-backed securities $ 129,617 1,337 10,253 $ 5,273 $ 146,480

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	BORROWINGS The following table summarizes the Corporation's borrowings as of December 31, 2017 and 2016: December 31, 2017 December 31, 2016 Federal funds purchased $ 144,038 $ 120,349 Securities sold under repurchase agreements 136,623 146,480 Federal Home Loan Bank advances 414,377 298,923 Subordinated debentures and term loans 139,349 128,445 Total Borrowings $ 834,387 $ 694,197 Securities sold under repurchase agreements consist of obligations of the Bank to other parties and are secured by U.S. Government-Sponsored Enterprise obligations. The maximum amount of outstanding agreements at any month-end during 2017 and 2016 totaled $145,883,000 and $158,185,000 , respectively, and the average of such agreements totaled $134,401,000 and $145,379,000 during 2017 and 2016 , respectively. Contractual maturities of borrowings as of December 31, 2017 , are as follows: Maturities in Years Ending December 31: Federal Funds Purchased Securities Sold Federal Home Subordinated 2018 $ 144,038 $ 136,623 $ 171,391 2019 121,713 2020 41,273 2021 25,000 2022 20,000 After 2022 35,000 $ 143,430 ASC 805 fair value adjustments at acquisition (4,081 ) $ 144,038 $ 136,623 $ 414,377 $ 139,349 The terms of a security agreement with the FHLB require the Corporation to pledge, as collateral for advances, qualifying first mortgage loans, investment securities and multi-family loans in an amount equal to at least 142 percent of these advances depending on the type of collateral pledged. Advances, with interest rates from 0.88 to 5.86 percent, are subject to restrictions or penalties in the event of prepayment. The total available remaining borrowing capacity from the FHLB at December 31, 2017 , was $664,177,000 . As of December 31, 2017 , the Corporation had $45,000,000 of putable advances with the FHLB. Subordinated Debentures and Term Loans. As of December 31, 2017 and 2016 , subordinated debentures and term loans totaled $139,349,000 and $ 128,445,000 , respectively. • First Merchants Capital Trust II. The subordinated debenture was entered into on July 2, 2007 for $56,702,000 . On August 10, 2015, the Corporation completed the cancellation of $5 million of subordinated debentures at a gain of $1,250,000 . As of December 31, 2017 , $51,702,000 of subordinated debentures remain outstanding with a maturity date of September 15, 2037. The Corporation could not redeem the debenture prior to September 15, 2012, and redemption is subject to the prior approval of the Board of Governors of the Federal Reserve System, as required by law or regulation. Interest was fixed at 6.495 percent for the period from the date of issuance through September 15, 2012; interest is now an annual floating rate equal to the three-month LIBOR plus 1.56 percent , reset quarterly. Interest is payable in March, June, September and December of each year. The interest rate at December 31, 2017 and 2016 was 3.15 percent and 2.52 percent , respectively. The Corporation holds all of the outstanding common securities of First Merchants Capital Trust II. • Ameriana Capital Trust I. On December 31, 2015 the Corporation acquired Ameriana Capital Trust I in conjunction with its acquisition of Ameriana Bancorp, Inc. The subordinated debentures of Ameriana Capital Trust I were entered into in March 2007 for $10,310,000 and have a maturity of March 2036. Ameriana could not redeem the debenture prior to March 2011, and redemption is subject to the prior approval of the Board of Governors of the Federal Reserve System, as required by law or regulation. The interest rate is equal to the three-month LIBOR plus 1.50 percent , reset quarterly. Interest is payable in March, June, September and December of each year. The interest rate at December 31, 2017 and 2016 was 3.09 percent and 2.46 percent , respectively. The Corporation holds all of the outstanding common securities of Ameriana Capital Trust I. • Grabill Capital Trust I. On July 14, 2017 the Corporation acquired Grabill Capital Trust I in conjunction with its acquisition of Independent Alliance Banks, Inc. The subordinated debentures of Grabill Capital Trust I were entered into in June 2004 for $10,310,000 and have a maturity of July 23, 2034. IAB could not redeem the debenture prior to July 2009, and redemption is subject to the prior approval of the Board of Governors of the Federal Reserve System, as required by law or regulation. The interest rate is equal to the three-month LIBOR plus 2.60 percent , reset quarterly. Interest is payable in January, April, July and October of each year. The interest rate at December 31, 2017 was 3.96 percent . The Corporation holds all of the outstanding common securities of Grabill Capital Trust I. • On November 1, 2013, the Corporation completed the private issuance and sale to four institutional investors of an aggregate of $70 million of debt comprised of (a) 5.00 percent Fixed-to-Floating Rate Senior Notes due 2028 in the aggregate principal amount of $5 million (the "Senior Debt") and (b) 6.75 percent Fixed-to -Floating Rate Subordinated Notes due 2028 in the aggregate principal amount of $65 million (the "Subordinated Debt"). The interest rate on the Senior Debt and Subordinated Debt remains fixed for the first ten ( 10 ) years and will become floating thereafter. Once the rates convert to floating on October 30, 2023, the Senior Debt will have an annual floating rate equal to the three-month LIBOR plus 2.345 percent and the Subordinated Debt will have an annual floating rate equal to the three-month LIBOR plus 4.095 percent . The Corporation has an option to redeem the Subordinated Debt in whole or in part at a redemption price equal to 100 percent of the principal amount of the redeemed Subordinated Notes, plus accrued and unpaid interest to the date of the redemption. The option of redemption is subject to the approval of the Federal Reserve Board. The Corporation has an option to redeem the Senior Debt in whole or in part at a redemption price equal to 100 percent of the principal amount of the redeemed Senior Notes, plus accrued and unpaid interest to the date of the redemption; provided, however, that no Subordinated Notes (as defined in the Issuing and Paying Agency Agreement) may remain outstanding subsequent to any early redemption of Senior Notes. The Subordinated Debt and the Senior Debt options to redeem begin with the interest payment date on October 30, 2023, or on any scheduled interest payment date thereafter. The Senior Debt agreement contains certain customary representations and warranties and financial and negative covenants. As of December 31, 2017 and 2016 the Corporation was in compliance with these covenants.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES Risk Management Objective of Using Derivatives The Corporation is exposed to certain risks arising from both its business operations and economic conditions. The Corporation principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Corporation manages economic risks, including interest rate, liquidity, and credit risk, primarily by managing the amount, sources, and duration of its assets and liabilities and through the use of derivative financial instruments. Specifically, the Corporation enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Corporation’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the Corporation’s known or expected cash payments principally related to certain variable-rate liabilities. The Corporation also has derivatives that are a result of a service the Corporation provides to certain qualifying customers, and, therefore, are not used to manage interest rate risk in the Corporation’s assets or liabilities. The Corporation manages a matched book with respect to its derivative instruments offered as a part of this service to its customers in order to minimize its net risk exposure resulting from such transactions. Cash Flow Hedges of Interest Rate Risk The Corporation’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Corporation primarily uses interest rate swaps and interest rate caps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the payment of fixed amounts to a counterparty in exchange for the Corporation receiving variable payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up-front premium. As of December 31, 2017 and 2016 , the Corporation had five interest rate swaps with a notional amount of $56.0 million and one interest rate cap with a notional amount of $13.0 million . The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During 2017 , $26.0 million of the interest rate swaps and the $13.0 million interest rate cap were used to hedge the variable cash outflows (LIBOR-based) associated with existing trust preferred securities when the outflows converted from a fixed rate to variable rate in September 2012 . In addition, the remaining $30.0 million of interest rate swaps were used to hedge the variable cash outflows (LIBOR-based) associated with three Federal Home Loan Bank advances. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. During the years ended December 31, 2017 and 2016 , the Corporation did not recognize any ineffectiveness. Amounts reported in accumulated other comprehensive income related to derivatives will be reclassified to interest expense as interest payments are made on the Corporation’s variable-rate liabilities. During the next twelve months, the Corporation expects to reclassify $640,000 from accumulated other comprehensive income to interest expense. Non-designated Hedges The Corporation does not use derivatives for trading or speculative purposes. Derivatives not designated as hedges are not speculative and result from a service the Corporation provides to certain customers. The Corporation executes interest rate swaps with commercial banking customers to facilitate their respective risk management strategies. Those interest rate swaps are simultaneously hedged by offsetting interest rate swaps that the Corporation executes with a third party, such that the Corporation minimizes its net risk exposure resulting from such transactions. As the interest rate swaps associated with this program do not meet the strict hedge accounting requirements, changes in the fair value of both the customer swaps and the offsetting swaps are recognized directly in earnings. As of December 31, 2017 , the notional amount of customer-facing swaps was approximately $396,206,000 . This amount is offset with third party counterparties, as described above. Fair Values of Derivative Instruments on the Balance Sheet The table below presents the fair value of the Corporation’s derivative financial instruments as well as their classification on the Balance Sheet as of December 31, 2017 and December 31, 2016 . Asset Derivatives Liability Derivatives December 31, 2017 December 31, 2016 December 31, 2017 December 31, 2016 Balance Sheet Location Fair Balance Sheet Location Fair Balance Sheet Location Fair Balance Sheet Location Fair Derivatives designated as hedging instruments: Interest rate contracts Other Assets $ 18 Other Assets $ 15 Other Liabilities $ 1,383 Other Liabilities $ 2,182 Derivatives not designated as hedging instruments: Interest rate contracts Other Assets $ 7,305 Other Assets $ 6,295 Other Liabilities $ 7,305 Other Liabilities $ 6,295 The amount of gain (loss) recognized in other comprehensive income is included in the table below for the periods indicated. Derivatives in Cash Flow Hedging Relationships Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivative 2017 2016 Interest rate products $ 13 $ (368 ) Effect of Derivative Instruments on the Income Statement The tables below present the effect of the Corporation’s derivative financial instruments on the Income Statement for the years ended December 31, 2017 , 2016 and 2015 . Derivatives Not Location of Gain Amount of Gain (Loss) Recognized in Income on Derivative 2017 2016 2015 Interest rate contracts Other income $ — $ 211 $ (53 ) Derivatives Designated as Hedging Location of Loss Reclassified from Accumulated Other Comprehensive Income (Effective Portion) Amount of Loss Reclassified from Other Comprehensive Income into Income (Effective Portion) 2017 2016 2015 Interest rate contracts Interest expense $ (985 ) $ (1,250 ) $ (1,427 ) The Corporation’s exposure to credit risk occurs because of nonperformance by its counterparties. The counterparties approved by the Corporation are usually financial institutions, which are well capitalized and have credit ratings through Moody’s and/or Standard & Poor’s, at or above investment grade. The Corporation’s control of such risk is through quarterly financial reviews, comparing mark-to-market values with policy limitations, credit ratings and collateral pledging. Credit-Risk-Related Contingent Features The Corporation has agreements with certain of its derivative counterparties that contain a provision where if the Corporation fails to maintain its status as a well/adequately capitalized institution, then the Corporation could be required to terminate or fully collateralize all outstanding derivative contracts. Additionally, the Corporation has agreements with certain of its derivative counterparties that contain a provision where if the Corporation defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Corporation could also be declared in default on its derivative obligations. As of December 31, 2017 , the termination value of derivatives in a net liability position related to these agreements was $2,579,000 . As of December 31, 2017 , the Corporation has minimum collateral posting thresholds with certain of its derivative counterparties and has posted collateral of $11,866,000 . If the Corporation had breached any of these provisions at December 31, 2017 , it could have been required to settle its obligations under the agreements at their termination value.

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	FAIR VALUES OF FINANCIAL INSTRUMENTS The Corporation used fair value measurements to record fair value adjustments, to certain assets, and liabilities and to determine fair value disclosures. The accounting guidance defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements. ASC 820 applies only when other guidance requires or permits assets or liabilities to be measured at fair value; it does not expand the use of fair value in any new circumstances. As defined in ASC 820, fair value is the price to sell an asset or transfer a liability in an orderly transaction between market participants. It represents an exit price at the measurement date. Market participants are buyers and sellers, who are independent, knowledgeable, and willing and able to transact in the principal (or most advantageous) market for the asset or liability being measured. Current market conditions, including imbalances between supply and demand, are considered in determining fair value. The Corporation values its assets and liabilities in the principal market where it sells the particular asset or transfers the liability with the greatest volume and level of activity. In the absence of a principal market, the valuation is based on the most advantageous market for the asset or liability (i.e., the market where the asset could be sold or the liability transferred at a price that maximizes the amount to be received for the asset or minimizes the amount to be paid to transfer the liability). Valuation inputs refer to the assumptions market participants would use in pricing a given asset or liability. Inputs can be observable or unobservable. Observable inputs are those assumptions which market participants would use in pricing the particular asset or liability. These inputs are based on market data and are obtained from a source independent of the Corporation. Unobservable inputs are assumptions based on the Corporation’s own information or estimate of assumptions used by market participants in pricing the asset or liability. Unobservable inputs are based on the best and most current information available on the measurement date. All inputs, whether observable or unobservable, are ranked in accordance with a prescribed fair value hierarchy which gives the highest ranking to quoted prices (unadjusted) in active markets for identical assets or liabilities (Level 1) and the lowest ranking to unobservable inputs for which there is little or no market activity (Level 3). Fair values for assets or liabilities classified as Level 2 are based on one or a combination of the following factors: (i) quoted prices for similar assets; (ii) observable inputs for the asset or liability, such as interest rates or yield curves; or (iii) inputs derived principally from or corroborated by observable market data. The level in the fair value hierarchy within which the fair value measurement in its entirety falls is determined based on the lowest level input that is significant to the fair value measurement in its entirety. The Corporation considers an input to be significant if it drives 10 percent or more of the total fair value of a particular asset or liability. RECURRING MEASUREMENTS Assets and liabilities are considered to be measured at fair value on a recurring basis if fair value is measured regularly (i.e., daily, weekly, monthly or quarterly). Recurring valuation occurs at a minimum on the measurement date. Assets and liabilities are considered to be measured at fair value on a non-recurring basis if the fair value measurement of the instrument does not necessarily result in a change in the amount recorded on the balance sheet. Generally, nonrecurring valuation is the result of the application of other accounting pronouncements which require assets or liabilities to be assessed for impairment or recorded at the lower of cost or fair value. The fair value of assets or liabilities transferred in or out of Level 3 is measured on the transfer date, with any additional changes in fair value subsequent to the transfer considered to be realized or unrealized gains or losses. Following is a description of the valuation methodologies used for instruments measured at fair value on a recurring basis and recognized in the accompanying balance sheets, as well as the general classification of such instruments pursuant to the valuation hierarchy. Investment Securities Where quoted prices are available in an active market, securities are classified within Level 1 of the valuation hierarchy. At December 31, 2017, there were no Level 1 securities. At December 31, 2016, Level 1 securities included equity securities. If quoted market prices are not available, then fair values are estimated by using pricing models, quoted prices of securities with similar characteristics or discounted cash flows. Level 2 securities included agencies, government-sponsored mortgage backs, state and municipal and equity securities. In certain cases where Level 1 or Level 2 inputs are not available, securities are classified within Level 3 of the hierarchy. Level 3 securities included state and municipal, corporate obligations and equity securities. Level 3 fair value for state and municipal, corporate obligations and equity securities was determined using a discounted cash flow model that incorporated market estimates of interest rates and volatility in markets that have not been active. Third party vendors compile prices from various sources and 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 specific investment securities but rather relying on the investment securities’ relationship to other benchmark quoted investment securities. Any investment security not valued based upon the methods above are considered Level 3. Interest Rate Derivative Agreements See information regarding the Corporation’s interest rate derivative products in NOTE 13. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES of these Notes to Consolidated Financial Statements. The following table presents the fair value measurements of assets and liabilities recognized in the accompanying balance sheets measured at fair value on a recurring basis and the level within the ASC 820-10 fair value hierarchy in which the fair value measurements fall at December 31, 2017 and 2016 . Fair Value Measurements Using: Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Available for sale securities: State and municipal $ 526,693 $ 522,750 $ 3,943 U.S. Government-sponsored mortgage-backed securities 470,866 470,866 Corporate obligations 31 31 Equity securities 2,357 2,353 4 Interest rate swap asset 7,305 7,305 Interest rate cap 18 18 Interest rate swap liability 8,688 8,688 Fair Value Measurements Using: Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Available for sale securities: U.S. Government-sponsored agency securities $ 100 $ 100 State and municipal 363,658 358,524 $ 5,134 U.S. Government-sponsored mortgage-backed securities 312,292 312,292 Corporate obligations 31 31 Equity securities 20,781 $ 18,765 2,012 4 Interest rate swap asset 6,295 6,295 Interest rate cap 15 15 Interest rate swap liability 8,477 8,477 LEVEL 3 RECONCILIATION The following is a reconciliation of the beginning and ending balances of recurring fair value measurements recognized in the accompanying balance sheets using significant unobservable Level 3 inputs for year ended December 31, 2017 and 2016 . Available for Sale Securities For The Year Ended December 31, 2017 December 31, 2016 Beginning Balance $ 5,169 $ 5,932 Included in other comprehensive income 26 (223 ) Principal payments (1,217 ) (540 ) Ending balance $ 3,978 $ 5,169 There were no gains or losses included in earnings that were attributable to the changes in unrealized gains or losses related to assets or liabilities held at December 31, 2017 or 2016 . TRANSFERS BETWEEN LEVELS There were no transfers in or out of Level 3 during 2017 or 2016. NONRECURRING MEASUREMENTS Following is a description of valuation methodologies used for instruments measured at fair value on a non-recurring basis and recognized in the accompanying balance sheets, as well as the general classification of such instruments pursuant to the valuation hierarchy for year ended December 31, 2017 and 2016 . Fair Value Measurements Using Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Impaired Loans (collateral dependent) $ 9,576 $ 9,576 Other real estate owned $ 859 $ 859 Fair Value Measurements Using Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Impaired Loans (collateral dependent) $ 15,318 $ 15,318 Other real estate owned $ 1,612 $ 1,612 Impaired Loans (collateral dependent) Loans for which it is probable that the Corporation will not collect all principal and interest due according to contractual terms are measured for impairment. Allowable methods for determining the amount of impairment include estimating fair value of the collateral for collateral dependent loans. If the impaired loan is identified as collateral dependent, then the fair value method of measuring the amount of impairment is utilized. This method requires obtaining a current independent appraisal of the collateral and applying a discount factor to the value. A portion of the allowance for loan losses is allocated to impaired loans if the value of such loans is deemed to be less than the unpaid balance. If these allocations cause the allowance for loan losses to increase, such increase is reported as a component of the provision for loan losses. Loan losses are charged against the allowance when management believes the uncollectability of the loan is confirmed. During 2017 , certain impaired loans were partially charged off or re-evaluated. Impaired loans that are collateral dependent are classified within Level 3 of the fair value hierarchy when impairment is determined using the fair value method. Other Real Estate Owned The fair value for impaired loans and other real estate owned is measured based on the value of the collateral securing those loans or real estate and is determined using several methods. The fair value of real estate is generally determined based on appraisals by qualified licensed appraisers. The appraisers typically determine the value of the real estate by utilizing an income or market valuation approach. If an appraisal is not available, the fair value may be determined by using a discounted cash flow analysis. Fair value on other collateral such as business assets is typically ascertained by assessing, either singularly or some combination of, asset appraisals, accounts receivable aging reports, inventory listings and or customer financial statements. Both appraised values and values based on borrower’s financial information are discounted as considered appropriate based on age and quality of the information and current market conditions. UNOBSERVABLE (LEVEL 3) INPUTS The following table presents quantitative information about unobservable inputs used in recurring and nonrecurring Level 3 fair value measurements, other than goodwill, at December 31, 2017 and 2016 . December 31, 2017 Fair Value Valuation Technique Unobservable Inputs Range (Weighted-Average) State and municipal securities $ 3,943 Discounted cash flow Maturity Call Date 1 month to 20 years Corporate obligations and Equity securities $ 35 Discounted cash flow Risk free rate 3 month LIBOR Impaired loans (collateral dependent) $ 9,576 Collateral based measurements Discount to reflect current market conditions and ultimate collectability 0% - 10% (1%) Other real estate owned $ 859 Appraisals Discount to reflect current market conditions 0% - 10% (2%) December 31, 2016 Fair Value Valuation Technique Unobservable Inputs Range (Weighted-Average) State and municipal securities $ 5,134 Discounted cash flow Maturity Call Date 1 month to 20 years Corporate obligations and Equity securities $ 35 Discounted cash flow Risk free rate 3 month LIBOR Impaired loans (collateral dependent) $ 15,318 Collateral based measurements Discount to reflect current market conditions and ultimate collectability 0% - 10% (1%) Other real estate owned $ 1,612 Appraisals Discount to reflect current market conditions 0% - 10% (9%) The following is a discussion of the sensitivity of significant unobservable inputs, the interrelationships between those inputs and other unobservable inputs used in recurring fair value measurement and how those inputs might magnify or mitigate the effect of changes in the unobservable inputs on the fair value measurement. State and Municipal Securities, Corporate Obligations and Equity Securities The significant unobservable inputs used in the fair value measurement of the Corporation's state and municipal securities, corporate obligations and equity securities are premiums for unrated securities and marketability discounts. Significant increases or decreases in either of those inputs in isolation would result in a significantly lower or higher fair value measurement. Generally, changes in on input will not affect the other input. FAIR VALUE OF FINANCIAL INSTRUMENTS The following table presents estimated fair values of the Corporation's financial instruments and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2017 and 2016 . 2017 Carrying Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets at December 31: Cash and cash equivalents $ 154,905 $ 154,905 Interest-bearing time deposits 35,027 35,027 Investment securities available for sale 999,947 $ 995,969 $ 3,978 Investment securities held to maturity 560,655 556,305 11,903 Loans held for sale 7,216 7,216 Loans 6,676,167 6,534,877 Federal Home Loan Bank stock 23,825 23,825 Interest rate swap asset 7,323 7,323 Interest receivable 37,130 37,130 Liabilities at December 31: Deposits $ 7,172,530 $ 5,741,019 $ 1,406,526 Borrowings: Federal funds purchased 144,038 144,038 Securities sold under repurchase agreements 136,623 136,562 Federal Home Loan Bank advances 414,377 361,085 Subordinated debentures and term loans 139,349 120,085 Interest rate swap liability 8,688 8,688 Interest payable 4,390 4,390 2016 Carrying Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets at December 31: Cash and cash equivalents $ 127,927 $ 127,927 Interest-bearing time deposits 24,459 24,459 Investment securities available for sale 696,862 18,765 $ 672,928 $ 5,169 Investment securities held to maturity 607,643 597,246 14,687 Loans held for sale 2,929 2,929 Loans 5,073,608 4,933,552 Federal Home Loan Bank stock 17,964 17,964 Interest rate swap asset 6,310 6,310 Interest receivable 26,194 26,194 Liabilities at December 31: Deposits $ 5,556,498 $ 4,427,605 $ 1,111,491 Borrowings: Federal funds purchased 120,349 120,349 Securities sold under repurchase agreements 146,480 146,449 Federal Home Loan Bank advances 298,923 297,465 Subordinated debentures and term loans 128,445 105,930 Interest rate swap liability 8,477 8,477 Interest payable 3,110 3,110 The following methods were used to estimate the fair value of all other financial instruments recognized in the Consolidated Balance Sheets at amounts other than fair value. Cash and cash equivalents : The fair value of cash and cash equivalents approximates carrying value. Interest-bearing time deposits : The fair value of interest-bearing time deposits approximates carrying value. Investment securities : Fair value is based on quoted market prices, if available. If a quoted market price is not available, fair value is estimated using quoted market prices for similar securities. The fair value of certain Level III securities is estimated using discounted cash flow analysis, using interest rates currently being offered on investments with similar maturities and investment quality. Loans held for sale : The carrying amount approximates fair value due to the short duration between origination and date of sale. Loans: The fair value for loans is estimated using discounted cash flow analysis, using interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. See Impaired Loans above. Federal Home Loan Bank stock : The fair value of Federal Home Loan Bank stock is based on the price which it may be resold to the Federal Home Loan Bank. Derivative instruments : The fair value of interest rate swaps reflect the estimated amounts that would have been received to terminate these contracts at the reporting date based upon pricing or valuation models applied to current market information. Interest rate caps are valued using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rose above the strike rate of the caps. The projected cash receipts on the caps are based on an expectation of future interest rates derived from observed market interest rate curves and volatilities. Interest receivable and Interest payable : The fair value of interest receivable/payable approximates carrying value. Deposits: The fair values of noninterest-bearing and interest-bearing demand accounts and savings deposits are equal to the amount payable on demand at the balance sheet date. The carrying amounts for variable rate, fixed-term certificates of deposit approximate their fair values at the balance sheet date. Fair values for fixed-rate certificates of deposit and other time deposits are estimated using a discounted cash flow calculation that applies interest rates currently being offered to a schedule of aggregated expected monthly maturities on such time deposits. Borrowings: The fair value of Federal Funds purchased approximates the carrying amount. The fair value of all other borrowings is estimated using a discounted cash flow calculation, based on current rates for similar debt.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	COMMITMENTS AND CONTINGENT LIABILITIES In the normal course of business there are outstanding commitments and contingent liabilities, such as commitments to extend credit and standby letters of credit, which are not included in the accompanying financial statements. The Corporation's exposure to credit loss in the event of nonperformance by the other party to the financial instruments for commitments to extend credit and standby letters of credit is represented by the contractual or notional amount of those instruments. The Bank uses the same credit policies in making such commitments as they do for instruments that are included in the consolidated balance sheets. Financial instruments, whose contract amount represents credit risk as of December 31, were as follows: 2017 2016 Amounts of commitments: Loan commitments to extend credit $ 2,482,641 $ 2,057,878 Standby letters of credit $ 43,526 $ 46,010 Commitments to extend credit are agreements to lend to a customer, as long as there is no violation of any condition established in the contract. 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 Bank evaluates each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the Bank upon extension of credit, is based on management's credit evaluation. Collateral held varies, but may include accounts receivable, inventory, property and equipment, and income-producing commercial properties. Standby letters of credit are conditional commitments issued by the Bank to guarantee the performance of a customer to a third party. The Corporation and subsidiaries are also subject to claims and lawsuits, which arise primarily in the ordinary course of business. It is the opinion of management that the disposition or ultimate resolution of such claims and lawsuits will not have a material adverse effect on the consolidated financial position of the Corporation.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table summarizes the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax, as of December 31, 2017 and 2016 : Accumulated Other Comprehensive Income (Loss) Unrealized Gains (Losses) on Securities Available for Sale Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Defined Benefit Plans Total Balance at December 31, 2016 $ 1,035 $ (1,774 ) $ (12,842 ) $ (13,581 ) Other comprehensive income before reclassifications 9,645 9 2,686 12,340 Amounts reclassified from accumulated other comprehensive income (1,710 ) 640 (597 ) (1,667 ) Period change 7,935 649 2,089 10,673 Balance at December 31, 2017 $ 8,970 $ (1,125 ) $ (10,753 ) $ (2,908 ) Balance at December 31, 2015 $ 12,325 $ (2,347 ) $ (11,340 ) $ (1,362 ) Other comprehensive income before reclassifications (9,087 ) (240 ) (470 ) (9,797 ) Amounts reclassified from accumulated other comprehensive income (2,203 ) 813 (1,032 ) (2,422 ) Period change (11,290 ) 573 (1,502 ) (12,219 ) Balance at December 31, 2016 $ 1,035 $ (1,774 ) $ (12,842 ) $ (13,581 ) The following table presents the reclassification adjustments out of accumulated other comprehensive income (loss) that were included in net income in the Consolidated Condensed Statements of Income for the years ended December 31, 2017 , 2016 and 2015 : Amount Reclassified from Accumulated Other Comprehensive Income (Loss) For the Year Ended December 31, Details about Accumulated Other Comprehensive Income (Loss) Components 2017 2016 2015 Affected Line Item in the Statements of Income Unrealized gains (losses) on available for sale securities (1) Realized securities gains reclassified into income $ 2,631 $ 3,389 $ 2,670 Other income - net realized gains on sales of available for sale securities Related income tax expense (921 ) (1,186 ) (934 ) Income tax expense $ 1,710 $ 2,203 $ 1,736 Unrealized gains (losses) on cash flow hedges (2) Interest rate contracts $ (985 ) $ (1,250 ) $ (1,427 ) Interest expense - subordinated debentures and term loans Related income tax benefit 345 437 499 Income tax expense $ (640 ) $ (813 ) $ (928 ) Unrealized gains (losses) on defined benefit plans Amortization of net loss and prior service costs $ 806 $ 1,588 $ 305 Other expenses - salaries and employee benefits Related income tax benefit (expense) (209 ) (556 ) (107 ) Income tax expense $ 597 $ 1,032 $ 198 Total reclassifications for the period, net of tax $ 1,667 $ 2,422 1,006 (1) For additional detail related to unrealized gains (losses) on available for sale securities and related amounts reclassified from accumulated other comprehensive income see NOTE 4. INVESTMENT SECURITIES. (2) For additional detail related to unrealized gains (losses) on cash flow hedges and related amounts reclassified from accumulated other comprehensive income see NOTE 13. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES.

Regulatory Capital and Dividend

Regulatory Capital and Dividends	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Regulatory Capital and Dividends	REGULATORY CAPITAL AND DIVIDENDS Regulatory Capital Capital adequacy is an important indicator of financial stability and performance. The Corporation and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies and are assigned to a capital category. The assigned capital category is largely determined by four ratios that are calculated according to the regulations: total risk-based capital, tier 1 risk-based capital, common equity tier 1 capital, and tier 1 leverage ratios. The ratios are intended to measure capital relative to assets and credit risk associated with those assets and off-balance sheet exposures of the entity. The capital category assigned to an entity can also be affected by qualitative judgments made by regulatory agencies about the risk inherent in the entity's activities that are not part of the calculated ratios. There are five capital categories defined in the regulations, ranging from well capitalized to critically undercapitalized. Classification of a bank in any of the undercapitalized categories can result in actions by regulators that could have a material effect on a bank's operations. Quantitative measures established by regulation to ensure capital adequacy require the Bank to maintain minimum amounts and ratios of total and tier 1 capital to risk-weighted assets, and of tier 1 capital to average assets, or leverage ratio, all of which are calculated as defined in the regulations. Banks with lower capital levels are deemed to be undercapitalized, significantly undercapitalized or critically undercapitalized, depending on their actual levels. The appropriate federal regulatory agency may also downgrade a bank to the next lower capital category upon a determination that the bank is in an unsafe or unsound practice. Banks are required to monitor closely their capital levels and to notify their appropriate regulatory agency of any basis for a change in capital category. Basel III was effective for the Corporation on January 1, 2015. Basel III requires the Corporation and the Bank to maintain a minimum ratio of CET1 capital to risk weighted assets, as defined in the regulation. Under the new Basel III rules, in order to avoid limitations on capital distributions, including dividends, the Corporation must hold a capital conservation buffer above the adequately capitalized CET1 capital to risk-weighted assets ratio. The capital conservation buffer is being phased in from zero percent to 2.50 percent by 2019. As of January 1, 2017, the Corporation was required to hold a capital conservation buffer of 1.25 percent, which amount increases by 0.625 percent in each successive year until 2019. Under Basel III, the Corporation and Bank elected to opt-out of including AOCI in regulatory capital. As of December 31, 2017 , the Bank met all capital adequacy requirements to be considered well capitalized. There is no threshold for well capitalized status for bank holding companies. The Corporation's and Bank's actual and required capital ratios as of December 31, 2017 and December 31, 2016 were as follows: Prompt Corrective Action Thresholds Actual Adequately Capitalized Well Capitalized December 31, 2017 Amount Ratio Amount Ratio Amount Ratio Total risk-based capital to risk-weighted assets First Merchants Corporation $ 1,048,757 13.69 % $ 612,848 8.00 % N/A N/A First Merchants Bank 1,016,355 13.17 617,477 8.00 $ 771,847 10.00 % Tier 1 capital to risk-weighted assets First Merchants Corporation $ 908,725 11.86 % $ 459,636 6.00 % N/A N/A First Merchants Bank 941,323 12.20 463,108 6.00 $ 617,477 8.00 % Common equity tier 1 capital to risk-weighted assets First Merchants Corporation $ 842,806 11.00 % $ 344,727 4.50 % N/A N/A First Merchants Bank 941,323 12.20 347,331 4.50 $ 501,700 6.50 % Tier 1 capital to average assets First Merchants Corporation $ 908,725 10.43 % $ 348,407 4.00 % N/A N/A First Merchants Bank 941,323 10.83 347,794 4.00 $ 434,742 5.00 % Prompt Corrective Action Thresholds Actual Adequately Capitalized Well Capitalized December 31, 2016 Amount Ratio Amount Ratio Amount Ratio Total risk-based capital to risk-weighted assets First Merchants Corporation $ 851,521 14.21 % $ 479,470 8.00 % N/A N/A First Merchants Bank 800,598 13.30 481,490 8.00 $ 601,862 10.00 % Tier 1 capital to risk-weighted assets First Merchants Corporation $ 720,484 12.02 % $ 359,603 6.00 % N/A N/A First Merchants Bank 734,561 12.20 361,117 6.00 $ 481,490 8.00 % Common equity tier 1 capital to risk-weighted assets First Merchants Corporation $ 665,445 11.10 % $ 269,702 4.50 % N/A N/A First Merchants Bank 734,561 12.20 270,838 4.50 $ 391,210 6.50 % Tier 1 capital to average assets First Merchants Corporation $ 720,484 10.54 % $ 273,456 4.00 % N/A N/A First Merchants Bank 734,561 10.78 272,461 4.00 $ 340,576 5.00 % Management believes that all of the above capital ratios are meaningful measurements for evaluating the safety and soundness of the Corporation. Traditionally, the banking regulators have assessed bank and bank holding company capital adequacy based on both the amount and the composition of capital, the calculation of which is prescribed in federal banking regulations. The Federal Reserve focuses its assessment of capital adequacy on a component of Tier 1 capital known as CET1. Because the Federal Reserve has long indicated that voting common shareholders' equity (essentially Tier 1 risk-based capital less preferred stock and non-controlling interest in subsidiaries) generally should be the dominant element in Tier 1 risk-based capital, this focus on CET1 is consistent with existing capital adequacy categories. Tier I regulatory capital consists primarily of total stockholders’ equity and subordinated debentures issued to business trusts categorized as qualifying borrowings, less non-qualifying intangible assets and unrealized net securities gains or losses. Because these measures are not defined in GAAP, they are considered non-GAAP financial measures. Non-GAAP financial measures have inherent limitations, are not required to be uniformly applied, and are not audited. Although these non-GAAP financial measures are frequently used by investors to evaluate a company, they have limitations as analytical tools, and should not be considered in isolation, or as a substitute for analyses of results as reported under GAAP. For a reconciliation of GAAP measures to regulatory measures (non-GAAP), see additional details within the “Capital” section of Management’s Discussion and Analysis of Financial Condition and Results of Operations included as Item 7 of this Annual Report on Form 10-K. Dividends The Corporation's principal source of funds for dividend payments to shareholders is dividends received from the Bank. Banking regulations limit the maximum amount of dividends that a bank may pay without requesting prior approval of regulatory agencies. Under these regulations, the amount of dividends that may be paid in any calendar year is limited to the bank’s retained net income (as defined) for the current year plus those for the previous two years, subject to the capital requirements described above. As of December 31, 2017 , the amount available without prior regulatory approval for 2018 dividends from the Corporation’s subsidiaries (both banking and non-banking) was $154,949,000 . Additionally, the Corporation has a Dividend Reinvestment and Stock Purchase Plan, enabling stockholders to elect to have their cash dividends on all shares automatically reinvested in additional shares of the Corporation’s common stock. In addition, stockholders may elect to make optional cash payments up to an aggregate of $2,500 per quarter for the purchase of additional shares of common stock. The stock is credited to participant accounts at fair market value. Dividends are reinvested on a quarterly basis. Stock Repurchase Program On February 9, 2016, the Board of Directors of the Corporation approved a stock repurchase program of up to $15 million of the outstanding shares of the Corporation's common stock. The shares may be purchased from time to time in open market transactions at prevailing market prices in accordance with federal securities laws. The Corporation is not obligated to purchase any shares under the program, and the program may be discontinued at any time. The actual timing, number and share price of shares purchased under the repurchase program will be determined by the Corporation at its discretion and will depend upon such factors as the market price of the stock, general market and economic conditions and applicable legal requirements.

Loan Servicing

Loan Servicing	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Loan Servicing	LOAN SERVICING Mortgage loans serviced for others are not included in the accompanying consolidated balance sheets. The loans are serviced primarily for the Federal Home Loan Mortgage Corporation, Fannie Mae, Federal Home Loan Bank of Cincinnati and Federal Home Loan Bank of Indianapolis, and the unpaid balances totaled $549,618,000 , $369,592,000 and $312,204,000 at December 31, 2017 , 2016 and 2015 , respectively. The amount of capitalized servicing assets is considered immaterial.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION Stock options and RSAs have been issued to directors, officers and other management employees under the Corporation's 1999 Long-term Equity Incentive Plan and the 2009 Long-term Equity Incentive Plan. The stock options, which have a ten -year life, become 100 percent vested ranging from six months to two years and are fully exercisable when vested. Option exercise prices equal the Corporation's common stock closing price on NASDAQ on the date of grant. RSAs issued to employees and non-employee directors provide for the issuance of shares of the Corporation's common stock at no cost to the holder and generally vest after three years. The RSAs vest only if the employee is actively employed by the Corporation on the vesting date and, therefore, any unvested shares are forfeited. For non-employee directors, the RSA's vest only if the non-employee director remains as an active board member on the vesting date and, therefore, any unvested shares are forfeited. RSAs for employees and non-employee directors retired from the Corporation are either immediately vested at retirement or continue to vest after retirement, depending on the plan under which the shares were granted. Deferred Stock Units ("DSUs") can be credited to non-employee directors who elect to defer payment of compensation under the Corporation's 2008 Equity Compensation Plan for Non-employee Directors. DSUs credited are equal to the restricted shares that the non-employee director would have received under the plan. As of December 31, 2017 , the Corporation did not have any outstanding DSUs. The Corporation’s 2009 ESPP provides eligible employees of the Corporation and its subsidiaries an opportunity to purchase shares of common stock of the Corporation through quarterly offerings financed by payroll deductions. The price of the stock to be paid by the employees shall be equal to 85 percent of the average of the closing price of the Corporation’s common stock on each trading day during the offering period. However, in no event shall such purchase price be less than the lesser of an amount equal to 85 percent of the market price of the Corporation’s stock on the offering date or an amount equal to 85 percent of the market value on the date of purchase. Common stock purchases are made quarterly and are paid through advance payroll deductions up to a calendar year maximum of $25,000 . Compensation expense related to unvested share-based awards is recorded by recognizing the unamortized grant date fair value of these awards over the remaining service periods of those awards, with no change in historical reported fair values and earnings. Awards are valued at fair value in accordance with provisions of share-based compensation guidance and are recognized on a straight-line basis over the service periods of each award. To complete the exercise of vested stock options, RSA’s and ESPP options, the Corporation generally issues new shares from its authorized but unissued share pool. Share-based compensation for the years ended December 31, 2017 , 2016 , and 2015 was $2,827,000 , $2,600,000 , and $2,270,000 , respectively, and has been recognized as a component of salaries and benefits expense in the accompanying CONSOLIDATED STATEMENTS OF INCOME. Share-based compensation expense recognized in the CONSOLIDATED STATEMENTS OF INCOME is based on awards ultimately expected to vest and is reduced for estimated forfeitures. Share-based compensation guidance requires forfeitures to be estimated at the time of grant and revised, if necessary, in subsequent periods, if actual forfeitures differ from those estimates. Pre-vesting forfeitures were estimated to be approximately 2.8 percent for the year ended December 31, 2017 , based on historical experience. The following table summarizes the components of the Corporation's share-based compensation awards recorded as an expense and the income tax benefit of such awards. The income tax benefit increase for the year ended December 31, 2017 is due to the implementation of ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting . This ASU requires all income tax effects of awards to be recognized as income tax expense or benefit in the income statement when the awards vest or are settled. Implementation of the ASU was effective January 1, 2017 and resulted in approximately $935,000 of income tax benefit for the year ended December 31, 2017 . Years Ended December 31, 2017 2016 2015 Stock and ESPP Options Pre-tax compensation expense $ 121 $ 76 $ 101 Income tax expense (benefit) (322 ) 18 4 Stock and ESPP option expense, net of income taxes $ (201 ) $ 94 $ 105 Restricted Stock Awards Pre-tax compensation expense $ 2,706 $ 2,524 $ 2,169 Income tax benefit (1,561 ) (883 ) (749 ) Restricted stock awards expense, net of income taxes $ 1,145 $ 1,641 $ 1,420 Total Share-Based Compensation: Pre-tax compensation expense $ 2,827 $ 2,600 $ 2,270 Income tax benefit (1,883 ) (865 ) (745 ) Total share-based compensation expense, net of income taxes $ 944 $ 1,735 $ 1,525 As of December 31, 2017 , unrecognized compensation expense related to RSAs was $6,090,000 and is expected to be recognized over weighted-average period of 1.45 years . The Corporation did no t have any unrecognized compensation expense related to stock options as of December 31, 2017 . Stock option activity under the Corporation's stock option plans, as of December 31, 2017 , and changes during the year ended December 31, 2017 , were as follows: Number of Weighted-Average Price Weighted Average Aggregate Outstanding at January 1, 2017 260,211 $ 19.26 Exercised (104,748 ) $ 22.90 Canceled (2,811 ) $ 22.21 Outstanding December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499 Vested and Expected to Vest at December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499 Exercisable at December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499 The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value (the difference between the Corporation's closing stock price on the last trading day of 2017 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their stock options on December 31, 2017 . The amount of aggregate intrinsic value will change based on the fair market value of the Corporation's common stock. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2017 and 2016 was $1,728,000 and $1,641,000 , respectively. Cash receipts of stock options exercised during 2017 and 2016 were $2,398,000 and $2,602,000 , respectively. The following table summarizes information on unvested RSAs outstanding as of December 31, 2017 : Number of Weighted-Average Unvested RSAs at January 1, 2017 328,347 $ 22.87 Granted 132,710 $ 40.47 Forfeited (4,702 ) $ 23.63 Vested (89,362 ) $ 20.53 Unvested RSAs at December 31, 2017 366,993 $ 29.79 The grant date fair value of ESPP options was estimated at the beginning of the October 1, 2017, quarterly offering period of approximately $28,000 . The ESPP options vested during the three months ending December 31, 2017 , leaving no unrecognized compensation expense related to unvested ESPP options at December 31, 2017 .

Pension and Other Post Retireme

Pension and Other Post Retirement Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension and Other Post Retirement Benefit Plans	PENSION AND OTHER POST RETIREMENT BENEFIT PLANS The Corporation’s defined-benefit pension plans cover approximately 15 percent of the Corporation’s employees. In 2005 , the Board of Directors of the Corporation approved the curtailment of the accumulation of defined benefits for future services provided by certain participants in the First Merchants Corporation Retirement Plan. No additional pension benefits have been earned by any employees who had not attained both the age of 55 and accrued at least 10 years of vesting service as of March 1, 2005 . The benefits are based primarily on years of service and employees’ pay near retirement. Contributions are intended to provide not only for benefits attributed to service-to-date, but also for those expected to be earned in the future. The Corporation also maintained a post retirement benefit plan that provided health insurance benefits to retirees. The plan allowed retirees to be carried under the Corporation’s health insurance plan, generally from ages 55 to 65 . The retirees paid 100 percent of the premiums due for their coverage. In 2016, the Corporation elected to terminate this plan effective December 31, 2017. The table below sets forth the plans’ funded status and amounts recognized in the consolidated balance sheets at December 31 , using measurement dates of December 31, 2017 and 2016 . 2017 2016 Change in Benefit Obligation: Benefit obligation at beginning of year $ 84,090 $ 71,747 Service cost 10 9 Interest cost 3,353 3,273 Actuarial loss 3,686 2,679 Benefits paid (5,179 ) (5,263 ) Plan settlements (3,803 ) Net transfers in from Ameriana acquisition 11,645 Benefit obligation at end of year $ 82,157 $ 84,090 Change in Plan Assets: Fair value of plan assets at beginning of year $ 83,557 $ 71,396 Actual return on plan assets 9,968 6,959 Employer contributions 670 739 Benefits paid (5,179 ) (5,263 ) Plan settlements (3,803 ) Ameriana acquisition 9,726 End of year 85,213 83,557 Funded status at end of year $ 3,056 $ (533 ) Assets and Liabilities Recognized in the Balance Sheets: Deferred tax asset $ 3,474 $ 7,041 Assets $ 7,660 $ 5,028 Liabilities $ 4,604 $ 5,561 Amounts Recognized in Accumulated Other Comprehensive Income Not Yet Recognized as Components of Net Periodic Cost, net of tax, consist of: Accumulated loss $ (10,360 ) $ (12,624 ) Prior service cost (393 ) (451 ) $ (10,753 ) $ (13,075 ) In 2017, the Corporation offered certain terminated vested pension plan participants the opportunity to elect a lump sum payment during a specific distribution window. The lump sums paid, or plan settlements, released $4.6 million of benefit obligation, while lump sum payments were $3.8 million . The total amount of lump sum payment elections and lump sums paid under regular operation of the plan, triggered pension plan settlement accounting, resulting in a $761,000 settlement charge, which is reflected in the Corporation's CONSOLIDATED STATEMENTS OF INCOME in the line titled "Salaries and employee benefits." Ameriana participated in the Pentegra Defined Benefit Plan for Financial Institutions (the "Pentegra Plan”), an industry-wide, tax-qualified defined-benefit pension plan. The Pentegra Plan operated as a multi-employer plan for accounting purposes and as a multiple employer plan under ERISA and the Internal Revenue Code. On November 20, 2015, Ameriana provided Pentegra a 60 -day written notice of withdrawal as a Participating Employer in the Pentegra Plan. Upon completion of the withdrawal from the Pentegra Plan, the assets and liabilities were merged into the First Merchants Corporation Retirement Plan in 2016. The accumulated benefit obligation for all defined benefit plans was $82,157,000 and $84,090,000 at December 31, 2017 and 2016 , respectively. Information for pension plans with an accumulated benefit obligation in excess of plan assets is included in the table below. December 31, 2017 December 31, 2016 Projected benefit obligation $ 4,604 $ 5,561 Accumulated benefit obligation $ 4,604 $ 5,561 Fair value of plan assets $ — $ — The following table shows the components of net periodic pension costs: December 31, 2017 December 31, 2016 December 31, 2015 Service cost $ 10 $ 9 $ 55 Interest cost 3,353 3,273 3,087 Expected return on plan assets (4,778 ) (4,508 ) (4,471 ) Amortization of prior service costs 90 79 64 Amortization of net loss 1,218 1,656 1,722 Settlement loss recognized 761 Net periodic pension cost $ 654 $ 509 $ 457 Other changes in plan assets and benefit obligations recognized in other comprehensive income: December 31, 2017 December 31, 2016 December 31, 2015 Net periodic pension cost $ 654 $ 509 $ 457 Net gain (loss) 1,504 (228 ) 1,299 Amortization of loss 1,979 1,656 1,722 Amortization of prior service cost 90 79 64 Total recognized in other comprehensive income 3,573 1,507 3,085 Total recognized in net periodic pension cost and other comprehensive income $ 2,919 $ 998 $ 2,628 The estimated net loss and transition obligation for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into net periodic pension cost over the next fiscal year are: December 31, 2017 December 31, 2016 December 31, 2015 Amortization of net loss $ (830 ) $ (1,208 ) $ (1,505 ) Amortization of prior service cost (87 ) (90 ) (61 ) Total $ (917 ) $ (1,298 ) $ (1,566 ) Significant assumptions include: December 31, 2017 December 31, 2016 December 31, 2015 Weighted-average Assumptions Used to Determine Benefit Obligation: Discount rate 3.60 % 4.20 % 4.50 % Rate of compensation increase for accruing active participants n/a 3.00 % 3.00 % Weighted-average Assumptions Used to Determine Cost: Discount rate 4.20 % 4.50 % 4.00 % Expected return on plan assets 6.00 % 6.00 % 6.00 % Rate of compensation increase for accruing active participants n/a 3.00 % 3.00 % At December 31, 2017 and 2016 , the Corporation based its estimate of the expected long-term rate of return on analysis of the historical returns of the plans and current market information available. The plans’ investment strategies are to provide for preservation of capital with an emphasis on long-term growth without undue exposure to risk. The assets of the plans’ are invested in accordance with the plans’ Investment Policy Statement, subject to strict compliance with ERISA and any other applicable statutes. The plans’ risk management practices include semi-annual evaluations of investment managers, including reviews of compliance with investment manager guidelines and restrictions; ability to exceed performance objectives; adherence to the investment philosophy and style; and ability to exceed the performance of other investment managers. The evaluations are reviewed by management with appropriate follow-up and actions taken, as deemed necessary. The Investment Policy Statement generally allows investments in cash and cash equivalents, real estate, fixed income debt securities and equity securities, and specifically prohibits investments in derivatives, options, futures, private placements, short selling, non-marketable securities and purchases of individual non-investment grade bonds. At December 31, 2017 , the maturities of the plans’ debt securities ranged from 15 days to 8.83 years , with a weighted average maturity of 4.53 years . At December 31, 2016 , the maturities of the plans’ debt securities ranged from 15 days to 8.03 years , with a weighted average maturity of 3.97 years . The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid as of December 31, 2017 . The minimum contribution required in 2018 will likely be zero , but the Corporation may decide to make a discretionary contribution during the year. 2018 $ 5,586 2019 5,641 2020 5,609 2021 5,476 2022 5,377 After 2022 25,652 $ 53,341 Plan assets are re-balanced quarterly. At December 31, 2017 and 2016 , plan assets by category are as follows: December 31, 2017 December 31, 2016 Actual Target Actual Target Cash and cash equivalents 6.0 % 3.0 % 4.5 % 3.0 % Equity securities 52.4 55.0 55.8 55.0 Debt securities 39.6 40.0 37.7 40.0 Alternative investments 2.0 2.0 2.0 2.0 100.0 % 100.0 % 100.0 % 100.0 % The Savings Plan, a Section 401(k) qualified defined contribution plan, was amended on March 1, 2005 to provide enhanced retirement benefits, including employer and matching contributions, for eligible employees of the Corporation and its subsidiaries. The Corporation matches employees’ contributions at the rate of 100 percent for the first 3 percent of base salary contributed by participants and 50 percent of the next 3 percent of base salary contributed by participants. Beginning in 2005 , employees who have completed 1000 hours of service and are an active employee on the last day of the year receive an additional retirement contribution after year-end. Employees hired after January 1, 2010 do not participate in the additional retirement contribution. Effective January 1, 2013, the additional retirement contribution was fixed at 2 percent. Full vesting occurs after five years of service. The Corporation’s expense for the Savings Plan, including the additional retirement contribution, was $3,691,000 , $3,441,000 and $3,526,000 for 2017 , 2016 and 2015 , respectively. The Corporation maintained a post retirement benefit plan that provided health insurance benefits to retirees. The plan allowed retirees to be carried under the Corporation’s health insurance plan, generally from ages 55 to 65 . The retirees paid 100 percent of the premiums due for their coverage. In 2016, the Corporation elected to terminate this plan effective December 31, 2017. As a result of the termination, in 2016, the Corporation recognized a curtailment gain of $2,157,000 as a component of "Salaries and benefits expense" in the accompanying CONSOLIDATED STATEMENTS OF INCOME. The obligation payable under the plan totaled $54,000 at December 31, 2016 . Post retirement plan expense totaled $(301,000) , $(2,437,000) and $(127,000) for the years ending December 31, 2017 , 2016 and 2015 , respectively. Pension Plan Assets Following is a description of the valuation methodologies used for pension plan assets measured at fair value on a recurring basis, as well as the general classification of pension plan assets pursuant to the valuation hierarchy. Where quoted market prices are available in an active market, plan assets are classified within Level 1 of the valuation hierarchy. Level 1 plan assets total $78,280,000 and $64,064,000 as of December 31, 2017 and 2016 , respectively, and include cash and cash equivalents, common stocks, mutual funds and corporate bonds and notes. If quoted market prices are not available, then fair values are estimated by using pricing models, quoted prices of plan assets with similar characteristics or discounted cash flows. Level 2 plan assets total $6,933,000 and $19,493,000 as of December 31, 2017 and 2016 , respectively, and include governmental agencies, taxable municipal bonds, common collective trust investments (which are classified below as Party-in-Interest Investments - common bond fund and common equity fund) and certificates of deposit. In certain cases where Level 1 or Level 2 inputs are not available, plan assets are classified within Level 3 of the hierarchy. There are no assets classified within Level 3 of the hierarchy at December 31, 2017 and 2016 . Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Cash & Cash Equivalents $ 5,123 $ 5,123 Corporate Bonds and Notes 14,598 14,598 Government Agency and Municipal Bonds and Notes 5,679 $ 5,679 Certificates of Deposit 1,254 1,254 Party-in-Interest Investments Common Stock 2,545 2,545 Mutual Funds Taxable Bond 12,198 12,198 Large Cap Equity 22,137 22,137 Mid Cap Equity 10,676 10,676 Small Cap Equity 5,264 5,264 International Equity 4,030 4,030 Specialty Alternative Equity 1,709 1,709 $ 85,213 $ 78,280 $ 6,933 Fair Value Measurements Using Quoted Prices in Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Cash & Cash Equivalents $ 3,778 $ 3,778 Corporate Bonds and Notes 10,646 10,646 Government Agency and Municipal Bonds and Notes 6,855 $ 6,855 Certificates of Deposit 1,268 1,268 Party-in-Interest Investments Common Stock 2,278 2,278 Common Bond Fund 4,744 4,744 Common Equity Fund 6,626 6,626 Mutual Funds Taxable Bond 7,974 7,974 Large Cap Equity 19,611 19,611 Mid Cap Equity 10,304 10,304 Small Cap Equity 4,680 4,680 International Equity 3,093 3,093 Specialty Alternative Equity 1,700 1,700 $ 83,557 $ 64,064 $ 19,493

Income Tax

Income Tax	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax	INCOME TAX The reconciliation between income tax expense expected at the U.S. federal statutory tax rate and the reported income tax expense is summarized in the following table for years ended December 31, 2017 , 2016 , 2015 : 2017 2016 2015 Reconciliation of Federal Statutory to Actual Tax Expense: Federal Statutory Income Tax at 35% $ 46,758 $ 38,031 $ 31,867 Tax-exempt Interest Income (11,127 ) (8,749 ) (7,083 ) Basis Difference on Sale of Insurance Subsidiary 2,252 Stock Compensation (893 ) (61 ) (31 ) Earnings on Life Insurance (2,302 ) (1,486 ) (1,012 ) Tax Credits (811 ) (564 ) (583 ) Tax Cuts and Jobs Act - Rate Reform Impact 5,120 Other 779 438 255 Income Tax Expense $ 37,524 $ 27,609 $ 25,665 Income tax expense consists of the following components for the years ended December 31, 2017 , 2016 , 2015 : 2017 2016 2015 Income Tax Expense for the Year Ended December 31: Currently Payable: Federal $ 22,001 $ 18,998 $ 21,221 State Deferred: Federal 9,969 8,233 3,952 Tax Cuts and Jobs Act - Rate Reform Impact 5,120 State 434 378 492 Income Tax Expense $ 37,524 $ 27,609 $ 25,665 Significant components of the net deferred tax assets (liabilities) resulting from temporary differences were as follows at December 31, 2017 and 2016 : 2017 2016 Deferred Tax Asset at December 31: Assets: Differences in Accounting for Loan Losses $ 19,526 $ 26,315 Differences in Accounting for Loan Fees 1,458 1,918 Differences in Accounting for Loans and Securities 3,681 5,689 Deferred Compensation 4,448 3,471 Difference in Accounting for Pensions and Other Employee Benefits 83 Federal & State Income Tax Loss Carryforward and Credits 10,829 16,643 Other 365 4,210 Total Assets 40,307 58,329 Liabilities: Differences in Depreciation Methods 5,245 8,216 Difference in Accounting for Pensions and Other Employee Benefits 823 State Income Tax 58 237 Net Unrealized Gain on Securities Available for Sale 2,898 557 Gain on FDIC Modified Whole Bank Transaction 602 1,126 Other 3,897 623 Total Liabilities 13,523 10,759 Net Deferred Tax Asset Before Valuation Allowance 26,784 47,570 Valuation allowance: Beginning Balance (9,815 ) (15,736 ) Decrease/(Increase) During the Year 2,849 5,921 Ending Balance (6,966 ) (9,815 ) Net Deferred Tax Asset $ 19,818 $ 37,755 The $17,937,000 decrease in the Corporation’s net deferred tax asset was due a combination of a decrease in deferred tax assets and an increase in deferred tax liabilities. The largest deferred tax asset decrease was associated with the impact of the Tax Cuts and Jobs Act ("TCJA"). Signed into law on December 22, 2017, the TCJA makes permanent a reduction in the federal corporate income tax rate from 35 percent to 21 percent. Under ASC 740, the Corporation is required to adjust its net deferred tax asset at December 31, 2017 to the enacted tax rate of 21 percent. As of December 31, 2017, the Corporation has substantially completed its accounting for the tax effects of enactment of the TCJA. Tax adjustments resulted in a decrease to the net deferred tax asset of $5,120,000 . The Corporation continues to analyze certain aspects of the TCJA and further refinements are possible, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. However, the Corporation does not expect these adjustments to materially impact our financial statements. Other decreases not related to the TCJA were associated with federal and state net operating loss carryforwards and other employee benefits of $2,323,000 and $2,080,000 , respectively. Increases in deferred tax liabilities associated with the accounting for acquisitions and accounting for unrealized gains on available for sale securities further decreased the net deferred tax asset by $4,106,000 and $4,273,000 , respectively. As of December 31, 2017 , the Corporation has approximately $45,196,000 of state NOL carryforwards available to offset future state taxable income, which will expire beginning in 2020 . These NOL carryforwards along with normal timing differences between book and tax result in total state deferred tax assets of $7,400,000 . Management believes it is more likely than not that the benefit from certain of these state NOL carryforwards and certain other state deferred tax assets will not be fully realized. In recognition of this risk, the Corporation has recorded a valuation allowance of $6,966,000 against its state deferred tax assets. The Corporation has additional paid-in capital that is considered restricted resulting from the acquisitions of CFS and Ameriana of approximately $13,393,000 and $11,883,000 , respectively. CFS and Ameriana qualified as banks under provisions of the Internal Revenue Code which permitted them to deduct from taxable income an allowance for bad debts which differed from the provision for losses charged to income. No provision for income taxes had been provided. If in the future this portion of additional paid-in capital is distributed, or the Corporation no longer qualifies as a bank for income tax purposes, income taxes may be imposed at the then applicable tax rates. The unrecorded deferred tax liability at December 31, 2017 , would have been approximately $5,308,000 . The Corporation or one of its subsidiaries files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Corporation is generally no longer subject to U.S. federal, state and local income tax examinations by tax authorities for tax years before 2014 .

Net Income Per Share

Net Income Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Per Share	NET INCOME PER SHARE Basic net income per share is computed by dividing net income by the weighted-average shares outstanding during the reporting period. Diluted net income per share is computed by dividing net income by the combination of all dilutive common share equivalents, comprised of shares issuable under the Corporation’s share-based compensation plans, and the weighted-average shares outstanding during the reporting period. Dilutive common share equivalents include the dilutive effect of in-the-money share-based awards, which are calculated based on the average share price for each period using the treasury stock method. Under the treasury stock method, the exercise price of share-based awards, the amount of compensation expense, if any, for future service that the Corporation has not yet recognized, and the amount of estimated tax benefits that would be recorded in additional paid-in capital when share-based awards are exercised, are assumed to be used to repurchase common stock in the current period. The following table reconciles basic and diluted net income per share for the years indicated: 2017 2016 2015 Weighted-Average Shares Weighted-Average Shares Weighted-Average Shares Basic net income per share: Net income available to common stockholders $ 96,070 45,181,221 $ 2.13 $ 81,051 40,767,343 $ 1.99 $ 65,384 37,816,399 $ 1.73 Effect of dilutive stock options and restricted stock awards 221,757 245,790 271,834 Diluted net income per share: Net income available to common stockholders $ 96,070 45,402,978 $ 2.12 $ 81,051 41,013,133 $ 1.98 $ 65,384 38,088,233 $ 1.72 As of December 31, 2017, there were no stock options with an option price greater than the average market price of the common shares. Options to purchase 51,949 and 286,119 shares of common stock, with weighted average exercise prices of $19.26 and $19.99 at December 31, 2016 and 2015 , respectively, were excluded from the computation of diluted net income per share because the options exercise price was greater than the average market price of the common stock.

Quarterly Results of Operations

Quarterly Results of Operations (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) The following table sets forth certain quarterly results for the years ended December 31, 2017 and 2016 : 2017 2016 First Second Third Fourth First Second Third Fourth Interest income $ 68,234 $ 71,467 $ 84,847 $ 90,348 $ 61,227 $ 62,704 $ 64,376 $ 65,005 Interest expense 7,235 8,367 10,427 11,583 6,772 6,742 6,694 6,631 Net interest income 60,999 63,100 74,420 78,765 54,455 55,962 57,682 58,374 Provision for loan losses 2,385 2,875 2,083 1,800 550 790 1,900 2,417 Net interest income after provision for loan losses 58,614 60,225 72,337 76,965 53,905 55,172 55,782 55,957 Non-interest income 14,846 18,434 18,668 19,061 15,837 16,385 16,861 16,120 Non-interest expense 43,099 47,316 58,708 56,433 46,475 44,835 44,115 41,934 Income before income tax expense 30,361 31,343 32,297 39,593 23,267 26,722 28,528 30,143 Income tax expense 7,168 7,207 7,939 15,210 5,574 6,716 7,469 7,850 Net income available to common stockholders $ 23,193 $ 24,136 $ 24,358 $ 24,383 $ 17,693 $ 20,006 $ 21,059 $ 22,293 Basic EPS $ 0.57 $ 0.57 $ 0.50 $ 0.49 $ 0.43 $ 0.50 $ 0.51 $ 0.55 Diluted EPS $ 0.56 $ 0.57 $ 0.50 $ 0.49 $ 0.43 $ 0.49 $ 0.51 $ 0.55 Average Shares Outstanding: Basic 40,984,481 42,038,824 48,431,880 49,144,310 40,690,573 40,751,720 40,779,423 40,846,650 Diluted 41,220,586 42,243,539 48,643,774 49,379,303 40,916,972 40,969,111 41,025,784 41,124,179

Condensed Financial Information

Condensed Financial Information (parent company only)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Financial Information (parent company only)	CONDENSED FINANCIAL INFORMATION (parent company only) Presented below is condensed financial information as to financial position, results of operations, and cash flows of the Corporation. Condensed Balance Sheets December 31, 2017 December 31, 2016 Assets Cash $ 31,527 $ 31,944 Investment in subsidiaries 1,411,360 978,291 Investment securities 31 18,765 Premises and equipment 1,252 1,260 Interest receivable 5 47 Goodwill 448 448 Cash surrender value of life insurance 787 1,082 Tax asset, deferred and receivable 521 Other assets 3,480 5,274 Total assets $ 1,448,890 $ 1,037,632 Liabilities Subordinated debentures and term loans $ 138,241 $ 127,427 Interest payable 968 880 Other liabilities 6,218 7,668 Total liabilities 145,427 135,975 Stockholders' equity 1,303,463 901,657 Total liabilities and stockholders' equity $ 1,448,890 $ 1,037,632 Condensed Statements of Income and Comprehensive Income December 31, 2017 December 31, 2016 December 31, 2015 Income Dividends from subsidiaries $ 33,014 $ 33,546 $ 39,032 Gain on the sale of insurance subsidiary 8,265 Gain on cancellation of subordinated debentures 1,250 Loss on sale of available for sale securities (50 ) Other income 350 143 197 Total income 33,314 33,689 48,744 Expenses Interest expense 7,572 7,185 6,661 Salaries and employee benefits 4,118 639 3,023 Net occupancy and equipment expenses 797 832 464 Other outside services 1,810 967 1,455 Professional services 442 279 636 Other expenses (385 ) (470 ) 1,234 Total expenses 14,354 9,432 13,473 Income before income tax benefit (expense) and equity in undistributed income of subsidiaries 18,960 24,257 35,271 Income tax benefit (expense) 5,946 3,243 (974 ) Income before equity in undistributed income of subsidiaries 24,906 27,500 34,297 Equity in undistributed income of subsidiaries 71,164 53,551 31,087 Net income available to common stockholders $ 96,070 $ 81,051 $ 65,384 Net income $ 96,070 $ 81,051 $ 65,384 Other comprehensive income (loss) 10,673 (12,219 ) 268 Comprehensive income $ 106,743 $ 68,832 $ 65,652 Condensed Statement of Cash Flows Year Ended December 31, 2017 2016 2015 Cash Flow From Operating Activities: Net income $ 96,070 $ 81,051 $ 65,384 Adjustments to Reconcile Net Income to Net Cash: Share-based compensation 1,215 1,166 843 Distributions in excess of (equity in undistributed) income of subsidiaries (71,164 ) (53,551 ) (31,087 ) Gain on sale of insurance subsidiary (8,265 ) Gain on cancellation of subordinated debentures (1,250 ) Loss on sale of available for sale securities 50 Net Change in: Other assets 3,358 833 (441 ) Other liabilities (1,900 ) 849 (1,486 ) Investment in subsidiaries - operating activities 1,112 (1,938 ) 197 Net cash provided by operating activities 28,741 28,410 23,895 Cash Flow From Investing Activities: Purchase of securities available for sale (19,804 ) Net cash received (paid) in acquisition 37 (14,500 ) Proceeds from business divestitures 16,000 Other 575 Net cash provided (used) in investing activities 37 (19,804 ) 2,075 Cash Flow From Financing Activities: Cash dividends (31,820 ) (22,203 ) (15,654 ) Repayment of borrowings (3,750 ) Stock issued under employee benefit plans 519 462 460 Stock issued under dividend reinvestment and stock purchase plan 991 835 661 Stock options exercised 2,398 2,602 1,531 Stock redeemed (1,283 ) (1,980 ) (1,640 ) Net cash used by financing activities (29,195 ) (20,284 ) (18,392 ) Cash, beginning of the year 31,944 43,622 36,044 Cash, end of year $ 31,527 $ 31,944 $ 43,622

Accounting Matters

Accounting Matters	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Accounting Matters	ACCOUNTING MATTERS The Corporation continually monitors potential accounting changes and pronouncements. The following pronouncements have been deemed to have the most applicability to the Corporation's financial statements: FASB Accounting Standards Updates No. 2018-02 - Income Statement - Reporting Comprehensive Income (Topic 220)-Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income Summary - The FASB issued an Accounting Standards Update (ASU) that helps organizations address certain stranded income tax effects in accumulated other comprehensive income (AOCI) resulting from the Tax Cuts and Jobs Act. ASU No. 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, provides financial statement preparers with an option to reclassify stranded tax effects within AOCI to retained earnings in 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 (or portion thereof) is recorded. The ASU requires financial statement preparers to disclose: • A description of the accounting policy for releasing income tax effects from AOCI; • Whether they elect to reclassify the stranded income tax effects from the Tax Cuts and Jobs Act; and • Information about the other income tax effects that are reclassified. The amendments affect any organization that is required to apply the provisions of Topic 220, Income Statement-Reporting Comprehensive Income, and has items of other comprehensive income for which the related tax effects are presented in other comprehensive income as required by GAAP. The amendments are effective for all organizations for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. Organizations should apply the proposed amendments either in the period of adoption or retrospectively to each period (or periods) 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. The Corporation adopted this ASU in the first quarter of 2018. Adoption of this ASU did not have a significant effect on the Corporation’s consolidated financial statements. FASB Accounting Standards Update No. 2017-12 - Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities Summary - The FASB has issued an Accounting Standards Update (ASU) No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The new standard is intended to improve and simplify accounting rules around hedge accounting. The ASU is effective for public companies in 2019 and private companies in 2020. Early adoption is permitted. The new standard refines and expands hedge accounting for both financial (e.g., interest rate) and commodity risks. Its provisions create more transparency around how economic results are presented, both on the face of the financial statements and in the footnotes, for investors and analysts. The new standard takes effect for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, for public companies and for fiscal years beginning after December 15, 2019 (and interim periods for fiscal years beginning after December 15, 2020), for private companies. Early adoption is permitted in any interim period or fiscal years before the effective date of the standard. The Corporation plans to adopt ASU 2017-12 in the first quarter of 2019. ASU 2017-12 requires a modified retrospective transition method in which the Corporation will recognize the cumulative effect of the change on the opening balance of each affected component of equity in the statement of financial position as of the date of adoption. While the Corporation continues to assess all potential impacts of the standard, adoption of the standard is not expected to have a significant effect on the Corporation’s consolidated financial statements. FASB Accounting Standards Update No. 2017-08 - Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities Summary - The FASB has issued Accounting Standards Update (ASU) No. 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. The ASU shortens the amortization period for certain callable debt securities held at a premium to the earliest call date. Under current GAAP, entities normally amortize the premium as an adjustment of yield over the contractual life of the instrument. Stakeholders have expressed concerns with the current approach on the basis that current GAAP excludes certain callable debt securities from consideration of early repayment of principal even if the holder is certain that the call will be exercised. As a result, upon the exercise of a call on a callable debt security held at a premium, the unamortized premium is recorded as a loss in earnings. Further, there is diversity in practice (1) in the amortization period for premiums of callable debt securities, and (2) in how the potential for exercise of a call is factored into current impairment assessments. Another issue is that the practice in the United States is to quote, price, and trade callable debt securities assuming a model that incorporates consideration of calls (also referred to as “yield-to-worst” pricing). The ASU shortens the amortization period for certain callable debt securities held at a premium and requires the premium to be amortized to the earliest call date. However, the amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. The amendments are effective for public business entities for annual periods beginning after December 15, 2018, including interim periods within those annual periods. For other entities, the amendments are effective for annual periods beginning after December 15, 2019, and interim periods within annual periods beginning after December 15, 2020. Early adoption is permitted. Entities are required to apply the amendments on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The entity is required to provide disclosures about a change in accounting principle in the period of adoption. The Corporation plans to adopt ASU 2017-08 in the first quarter of 2019. Adoption of this ASU is not expected to have a significant effect on the Corporation’s consolidated financial statements. FASB Accounting Standards Update No. 2017-07 - Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost Summary - The FASB has issued Accounting Standards Update (ASU) No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The amendments apply to all employers, including not-for-profit entities, that offer to their employees defined benefit pension plans, other postretirement benefit plans, or other types of benefits accounted for under Topic 715, Compensation - Retirement Benefits . The amendments require that an employer report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations, if one is presented. If a separate line item or items are used to present the other components of net benefit cost, that line item or items must be appropriately described. If a separate line item or items are not used, the line item or items used in the income statement to present the other components of net benefit cost must be disclosed. The amendments also allow only the service cost component to be eligible for capitalization when applicable (e.g., as a cost of internally manufactured inventory or a self-constructed asset). The amendments are effective for public business entities for annual periods beginning after December 15, 2017, including interim periods within those annual periods. For other entities, the amendments are effective for annual periods beginning after December 15, 2018, and interim periods within annual periods beginning after December 15, 2019. Early adoption is permitted as of the beginning of an annual period for which financial statements (interim or annual) have not been issued or made available for issuance. The Corporation adopted this ASU in the first quarter of 2018. Adoption of this ASU did not have a significant effect on the Corporation’s consolidated financial statements. FASB Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Summary - The FASB has issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This new guidance was issued to address concerns that current generally accepted accounting principles (GAAP) restricts the ability to record credit losses that are expected, but do not yet meet the “probable” threshold by replacing the current “incurred loss” model for recognizing credit losses with an “expected life of loan loss” model referred to as the Current Expected Credit Loss (CECL) model. Under the CECL model, certain financial assets carried at amortized cost, such as loans held for investment and held-to-maturity debt securities, are required to be presented at the net amount expected to be collected. The measurement of expected credit losses is to be based on information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. This measurement will take place at the time the financial asset is first added to the balance sheet and periodically thereafter. This differs significantly from the “incurred loss” model required under current GAAP, which delays recognition until it is probable a loss has been incurred. The change could materially affect how the allowance for loan losses is determined and cause a charge to earnings through the provision for loan losses. Such would adversely affect the financial condition of the Corporation. The ASU is effective for SEC filers for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019 (i.e., January 1, 2020, for calendar year entities). Early application will be permitted for all organizations for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Corporation plans to adopt this ASU in the first quarter of 2020. The impact of CECL adoption continues to be evaluated, but it’s expected a one-time cumulative-effect adjustment to the allowance for loan losses will be recognized in retained earnings on the consolidated balance sheet as of the beginning of the first reporting period in which the new standard is effective, as is consistent with regulatory expectations set forth in interagency guidance issued at the end of 2016. The magnitude of any such adjustment or the overall impact of the new standard on financial condition or results of operations cannot yet be determined. FASB Accounting Standards Update No. 2016-02 - Leases (Topic 842) Summary - The FASB has issued its new lease accounting guidance in Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842). Under the new guidance, lessees will be required to recognize the following for all leases (with the exception of short-term leases) at the commencement date: • A lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and • A right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under the new guidance, lessor accounting is largely unchanged. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, Revenue from Contracts with Customers. The new lease guidance simplified the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. Lessees will no longer be provided with a source of off-balance sheet financing. Public business entities should apply the amendments in ASU 2016-02 for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years (i.e., January 1, 2019, for a calendar year entity). Nonpublic business entities should apply the amendments for fiscal years beginning after December 15, 2019 (i.e., January 1, 2020, for a calendar year entity), and interim periods within fiscal years beginning after December 15, 2020. Early application is permitted for all public business entities and all nonpublic business entities upon issuance. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. Lessees and lessors may not apply a full retrospective transition approach. The Corporation plans to adopt this ASU in the first quarter of 2019. The impact of this ASU continues to be evaluated, but it’s expected a one-time adjustment to the Corporation’s other assets and other liabilities on the consolidated balance sheet will occur as of the beginning of the first reporting period in which the new standard is effective. The magnitude of any such adjustment or the overall impact of the new standard on financial condition, results of operations and regulatory capital is being evaluated. FASB Accounting Standards Updates No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities Summary - The FASB has issued Accounting Standards Update (ASU) No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new guidance is intended to improve the recognition and measurement of financial instruments. The ASU affects public and private companies, not-for-profit organizations, and employee benefit plans that hold financial assets or owe financial liabilities. The new guidance makes targeted improvements to existing U.S. GAAP by: • Requiring equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income; • Requiring public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; • Requiring separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (i.e., securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; • Eliminating the requirement to disclose the fair value of financial instruments measured at amortized cost for organizations that are not public business entities; • Eliminating the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and • Requiring a reporting organization to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk (also referred to as “own credit”) when the organization has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The new guidance is effective for public companies for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. For private companies, not-for-profit organizations, and employee benefit plans, the new guidance becomes effective for fiscal years beginning after December 15, 2018, and for interim periods within fiscal years beginning after December 15, 2019. The new guidance permits early adoption of the own credit provision. In addition, the new guidance permits early adoption of the provision that exempts private companies and not-for-profit organizations from having to disclose fair value information about financial instruments measured at amortized cost. The Corporation adopted this ASU in the first quarter of 2018. Adoption of this ASU did not have a significant effect on the Corporation’s consolidated financial statements. FASB Accounting Standards Updates No. 2014-09, Revenue from Contracts with Customers (Topic 606): Summary - The FASB has issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) . The amendments in this update supersede virtually all existing GAAP revenue recognition guidance, including most industry-specific revenue recognition guidance. ASU 2014-09 creates a single, principle-based revenue recognition framework and will require entities to apply significantly more judgment and expanded disclosures surrounding revenue recognition. The core principle requires an entity to recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those good or services. ASU 2014-09 applies to contracts with customers to provide goods and services, with certain exclusion such as lease contracts, financing arrangements and financial instruments. The amendments in ASU 2014-09 are effective for annual reporting periods beginning after December 15, 2017. Early adoption is permitted for annual reporting periods beginning after December 15, 2016. The Corporation’s revenue is comprised of net interest income on financial assets and financial liabilities, which is explicitly excluded from the scope of ASU 2014-09, and non-interest income. The revenue line items within the scope of this new guidance have been identified and the Corporation's accounting policies will not materially change since the principles of revenue recognition from the ASU are largely consistent with existing guidance and the Corporation's current practices. The Corporation has elected to implement using the modified retrospective application, with the cumulative effect recorded as an adjustment to opening retained earnings at January 1, 2018. Qualitative disclosures of performance obligations related to revenue recognition and disaggregation for significant categories of revenue will be presented according to the scope of the guidance.

General Litigation

General Litigation	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
General Litigation	GENERAL LITIGATION The Corporation is subject to claims and lawsuits that arise primarily in the ordinary course of business. It is the opinion of management that the disposition or ultimate resolution of such claims and lawsuits will not have a material adverse effect on the consolidated financial position, results of operations and cash flow of the Corporation.

Nature of Operations and Summ36

Nature of Operations and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Accounting	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Consolidation	CONSOLIDATION of the Corporation's financial statements include the accounts of the Corporation and all its subsidiaries, after elimination of all material intercompany transactions.
Business Combinations	BUSINESS COMBINATIONS are accounted for under the acquisition method of accounting. Under the acquisition method, assets and liabilities of the business acquired are recorded at their estimated fair values as of the date of acquisition with any excess of the cost of the acquisition over the fair value of the net tangible and intangible assets acquired recorded as goodwill. Results of operations of the acquired business are included in the income statement from the date of acquisition.
Available for Sale Securities	AVAILABLE FOR SALE SECURITIES are recorded at fair value on a recurring basis with the unrealized gains and losses, net of applicable income taxes, recorded in other comprehensive income. Realized gains and losses are recorded in earnings and the prior fair value adjustments are reclassified within stockholders' equity. Gains and losses on sales of securities are determined on the specific-identification method. Amortization of premiums and accretion of discounts are recorded as interest income from securities. Available for sale and held to maturity securities are evaluated for OTTI at least on a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. The investment securities portfolio is evaluated for OTTI by segregating the portfolio into two general segments and applying the appropriate OTTI model. Investment securities are generally evaluated for OTTI under ASC 320, Investments - Debt and Equity Securities . However, certain purchased beneficial interest, including certain non-agency government-sponsored mortgage-backed securities, asset-backed securities and collateralized debt obligations are evaluated using the model outlined in ASC 325-10, Investments - Other . In determining OTTI under ASC 320, management considers many factors, including: (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near term prospects of the issuer, (3) whether the market decline was affected by macroeconomic conditions, and (4) whether the Corporation has the intent to sell the debt security or more likely than not, will be required to sell the debt security before its anticipated recovery. The assessment of whether an other-than-temporary decline exists involves a high degree of subjectivity and judgment and is based on the information available to management at a point in time. When OTTI occurs, the amount of OTTI recognized in the income statement depends on whether the Corporation intends to sell the security or it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis, less any recognized credit loss. If the intent is to sell, or it is more likely than not that the Corporation will be required to sell the security before recovery of its amortized cost basis, less any recognized credit loss, the OTTI shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis, less any recognized credit loss, and its fair value at the balance sheet date. If the intent is not to sell the security and it is not more likely than not that the Corporation will be required to sell the security before the recovery of its amortized cost basis less any recognized credit loss, the OTTI has been separated into the amount representing the credit loss and the amount related to all other factors. The amount of the total OTTI related to the credit loss is determined based on the present value of cash flows expected to be collected and is recognized in earnings. The amount of the total OTTI related to other factors is recognized in other comprehensive income, net of applicable income taxes. The previous amortized cost basis less the OTTI recognized in earnings becomes the new amortized cost basis of the investment.
Held to Maturity Securities	HELD TO MATURITY SECURITIES are classified as held to maturity when the Corporation has the positive intent and ability to hold the securities to maturity. Securities held to maturity are carried at amortized cost. For held to maturity debt securities, the amount of an OTTI recorded in other comprehensive income for the noncredit portion of a previous other-than-temporary impairment is amortized prospectively over the remaining life of the security on the basis of the timing of future estimated cash flows of the security.
Loans Held for Sale	LOANS HELD FOR SALE are carried at the principal amount outstanding. The carrying amount approximates fair value due to the short duration between origination and the date of sale.
Loans	LOANS held in the Corporation’s portfolio are carried at the principal amount outstanding, net of unearned income. Certain non-accrual, substantially delinquent and renegotiated loans classified as troubled debt restructures may be considered to be impaired in accordance with ASC 310, Receivables . Under ASC 310, a loan is impaired when, based on current information or events, it is probable that the Bank will be unable to collect all amounts due (principal and interest) according to the contractual terms of the loan agreement. Renegotiated consumer loans classified as troubled debt restructures are considered to be impaired. In applying the provisions of ASC 310, the Corporation considers all other investments in one-to-four family residential loans and consumer installment loans to be homogeneous and therefore excluded from separate identification for evaluation of impairment. Interest income is accrued on the principal balances of loans. The accrual of interest is discontinued on a loan when, in management’s opinion, the borrower may be unable to meet payments as they become due. When the interest accrual is discontinued, all unpaid accrued interest is reversed against earnings when considered uncollectible. Interest income accrued in the prior year, if any, is charged to the allowance for loan losses. Interest income is subsequently recognized only to the extent cash payments are received and the loan is returned to accruing status. Certain loan fees and direct costs are being deferred and amortized as an adjustment of yield on the loans. Impaired loans are carried at the fair value of collateral if the loan is collateral dependent, or the present value of estimated future cash flows using the loan’s existing rate. A portion of the allowance for loan losses is allocated to impaired loans if the value of such loans is deemed to be less than the unpaid balance. If these allocations cause the allowance for loan losses to increase, such increase is reported as a component of the provision for loan losses. Loan losses are charged against the allowance when management believes the uncollectability of the loan is confirmed. The valuation would be considered Level 3, consisting of appraisals of underlying collateral and discounted cash flow analysis. Loan commitments and letters-of-credit generally have short-term, variable-rate features and contain clauses which limit the Bank’s exposure to changes in customer credit quality. Accordingly, their carrying values, which are immaterial at the respective balance sheet dates, are reasonable estimates of fair value.
Loans Acquired in Business Combinations	LOANS ACQUIRED IN BUSINESS COMBINATIONS with evidence of credit deterioration since origination and for which it is probable that all contractually required payments will not be collected are considered to be purchased credit impaired. Evidence of credit quality deterioration as of purchase dates may include information such as past-due and nonaccrual status, borrower credit scores and recent loan to value percentages. Acquired credit-impaired loans are accounted for under the accounting guidance for loans and debt securities acquired with deteriorated credit quality (ASC 310-30). These loans are initially measured at fair value based upon expected cash flows without anticipation of prepayments and includes estimated future credit losses expected to be incurred over the life of the loans. As a result, related discounts are recognized subsequently through accretion based on the expected cash flows of the acquired loans. For purposes of applying ASC 310-30, loans acquired in business combinations are individually evaluated for the initial fair value measurement. Accordingly, allowances for credit losses related to these loans are not carried over and recorded at the acquisition date. The difference between contractually required payments and the cash flows expected to be collected at acquisition is referred to as the nonaccretable portion of the fair value discount or premium. The accretable portion of the fair value discount or premium is the difference between the expected cash flows and the net present value of expected cash flows, with such difference accreted into earnings over the term of the loans. Acquired loans not accounted for under ASC 310-30 are accounted for under ASC 310-20, which allows the fair value adjustment to be accreted into income over the remaining life of the loans.
Allowance for Loan Losses	ALLOWANCE FOR LOAN LOSSES is maintained to absorb losses inherent in the loan portfolio and is based on ongoing, quarterly assessments of the probable losses inherent in the loan portfolio. The allowance is increased by the provision for loan losses, which is charged against current operating results. Loan losses are charged against the allowance when management believes the uncollectability of a loan balance is confirmed. Subsequent recoveries, if any, are credited to the allowance. The Corporation’s strategy for credit risk management includes credit policies and underwriting criteria for all loans, as well as an overall credit limit for each customer significantly below legal lending limits. The strategy also emphasizes diversification on regional geographic and industry levels, regular credit quality reviews and management reviews of large credit exposures and loans experiencing deterioration of credit quality. The Corporation’s methodology for assessing the appropriateness of the allowance consists of three key elements – the determination of the appropriate reserves for impaired loans accounted for under ASC 310, probable losses estimated from historical loss rates, and probable losses resulting from economic, environmental, qualitative or other deterioration above and beyond what is reflected in the first two components of the allowance. Commercial relationships greater than $500,000 that exhibit probable or observed credit weaknesses are subject to individual review. Where appropriate, reserves are allocated to individual loans based on management’s estimate of the borrower’s ability to repay the loan given the availability of collateral, other sources of cash flow and legal options available to the Corporation. Included in the review of individual loans are those that are impaired as provided in ASC 310. Any allowances for impaired loans are measured based on the fair value of the underlying collateral if collateral dependent or the present value of expected future cash flows discounted at the loan’s effective interest rate. The Corporation evaluates the collectability of principal when assessing the need for a loss accrual. Historical loss rates are applied to other commercial loans not subject to specific reserve allocations. The historical allocation for commercial loans graded pass are established by loan segments using loss rates based on the Corporation’s migration analysis. This migration analysis shows the loss rates for each segment of loans based on the loan grades at the beginning of the twelve month period. This loss rate is then applied to the current portfolio of loans in each respective loan segment. Homogenous loans, such as consumer installment and residential mortgage loans, are not individually risk graded. Reserves are established for each segment of loans using loss rates based on charge-offs for the same period as the migration analysis used for commercial loans. Historical loss allocations for commercial and consumer loans may be adjusted for significant factors that, in management’s judgment, reflect the impact of any current conditions on loss recognition. Factors which management considers in the analysis include the effects of the national and local economies, trends in loan growth and charge-off rates, changes in mix, concentration of loans in specific industries, asset quality trends (delinquencies, charge-offs and non-accrual loans), risk management and loan administration, changes in the internal lending policies and credit standards, examination results from bank regulatory agencies and the Corporation’s internal loan review.
Pension	PENSION benefits are provided to the Corporation’s employees. Its accounting policies related to pensions and other post retirement benefits reflect the guidance in ASC 715, Compensation – Retirement Benefits. The Corporation does not consolidate the assets and liabilities associated with the pension plan. Instead, the Corporation recognizes the funded status of the plan in the consolidated balance sheets. The measurement of the funded status and the annual pension expense involves actuarial and economic assumptions. Various statistical and other factors, which attempt to anticipate future events, are used in calculating the expense and liabilities related to the plans. Key factors include assumptions on the expected rates of return on plan assets, discount rates, expected rates of salary increases and health care costs and trends. The Corporation considers market conditions, including changes in investment returns and interest rates in making these assumptions. The primary assumptions used in determining the Corporation’s pension and post retirement benefit obligations and related expenses are presented in NOTE 20. PENSION AND OTHER POST RETIREMENT BENEFIT PLANS of these Notes to Consolidated Financial Statements.
Premises and Equipment	PREMISES AND EQUIPMENT is carried at cost net of accumulated depreciation. Depreciation is computed using the straight-line and declining balance methods based on the estimated useful lives of the assets ranging from three to forty years. Maintenance and repairs are expensed as incurred, while major additions and improvements, which extend the useful life, are capitalized. Gains and losses on dispositions are included in current operations.
Federal Home Loan Bank Stock	FEDERAL HOME LOAN BANK STOCK is a required investment for institutions that are members of the FHLB. The Bank is a member of the FHLB of Indianapolis. Members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security, and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income.
Intangible Assets	INTANGIBLE ASSETS that are subject to amortization, including core deposit intangibles, are being amortized on both the straight-line and accelerated basis over two to twenty years. Intangible assets are periodically evaluated as to the recoverability of their carrying value.
Goodwill	GOODWILL is maintained by applying the provisions of ASC 350, Intangibles – Goodwill and Other . For purchase acquisitions, the Corporation is required to record the assets acquired, including identified intangible assets, and the liabilities assumed at their fair value, which in many instances involves estimates based on third party valuations, such as appraisals, or internal valuations based on discounted cash flow analysis or other valuation techniques that may include estimates of attrition, inflation, asset growth rates or other relevant factors. In addition, the determination of the useful lives for which an intangible asset will be amortized is subjective. Under ASC 350, the Corporation is required to evaluate goodwill for impairment on an annual basis, as well as on an interim basis, if events or changes indicate that the asset may be impaired, indicating that the carrying value may not be recoverable. The Corporation has historically elected to test for goodwill impairment as of October 1 of each year and has determined that no impairment exists.
Bank Owned Life Insurance	BANK OWNED LIFE INSURANCE has been purchased on certain employees and directors of the Corporation. The Corporation records the life insurance at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or amounts due that are probable at settlement.
Other Real Estate Owned	OTHER REAL ESTATE OWNED consists of assets acquired through, or in lieu of, loan foreclosure and are held for sale. They are initially recorded at fair value less cost to sell at the date of foreclosure, establishing a new cost basis. Subsequent to foreclosure, valuations are periodically performed by management and the assets are carried at the lower of carrying amount or fair value less cost to sell. Revenue and expenses from operations and changes in the valuation are included in other real estate owned and foreclosure expenses. Other real estate owned also includes bank premises formerly, but no longer used for banking. Bank premises are transferred at the lower of carrying value or fair value less cost to sell.
Derivative Instruments	DERIVATIVE INSTRUMENTS are carried at the fair value of the derivatives and reflects the estimated amounts that would have been received to terminate these contracts at the reporting date based upon pricing or valuation models applied to current market information. As part of the asset/liability management program, the Corporation will utilize, from time to time, interest rate floors, caps or swaps to reduce its sensitivity to interest rate fluctuations. These are derivative instruments, which are recorded as assets or liabilities in the consolidated balance sheets at fair value. Changes in the fair values of derivatives are reported in the consolidated statements of operations or AOCI depending on the use of the derivative and whether the instrument qualifies for hedge accounting. The key criterion for the hedge accounting is that the hedged relationship must be highly effective in achieving offsetting changes in those cash flows that are attributable to the hedged risk, both at inception of the hedge and on an ongoing basis. Derivatives that qualify for the hedge accounting treatment are designated as either: a hedge of the fair value of the recognized asset or liability or of an unrecognized firm commitment (a fair value hedge) or a hedge of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (a cash flow hedge). To date, the Corporation has only entered into a cash flow hedge. For cash flow hedges, changes in the fair values of the derivative instruments are reported in AOCI to the extent the hedge is effective. The gains and losses on derivative instruments that are reported in AOCI are reflected in the consolidated statements of income in the periods in which the results of operations are impacted by the variability of the cash flows of the hedged item. Generally, net interest income is increased or decreased by amounts receivable or payable with respect to the derivatives, which qualify for hedge accounting. At inception of the hedge, the Corporation establishes the method it uses for assessing the effectiveness of the hedging derivative and the measurement approach for determining the ineffective aspect of the hedge. The ineffective portion of the hedge, if any, is recognized in the consolidated statements of income. The Corporation excludes the time value expiration of the hedge when measuring ineffectiveness. The Corporation offers interest rate derivative products (e.g. interest rate swaps) to certain of its high-quality commercial borrowers. This product allows customers to enter into an agreement with the Corporation to swap their variable rate loan to a fixed rate. These derivative products are designed to reduce, eliminate or modify the risk of changes in the borrower’s interest rate or market price risk. The extension of credit incurred through the execution of these derivative products is subject to the same approvals and rigorous underwriting standards as the related traditional credit product. The Corporation limits its risk exposure to these products by entering into a mirror-image, offsetting swap agreement with a separate, well-capitalized and rated counterparty previously approved by the Credit and Asset Liability Committee. By using these interest rate swap arrangements, the Corporation is also better insulated from the interest rate risk associated with underwriting fixed-rate loans. These derivative contracts are not designated against specific assets or liabilities under ASC 815, Derivatives and Hedging , and, therefore, do not qualify for hedge accounting. The derivatives are recorded on the balance sheet at fair value and changes in fair value of both the customer and the offsetting swap agreements are recorded (and essentially offset) in non-interest income. The fair value of the derivative instruments incorporates a consideration of credit risk (in accordance with ASC 820, Fair Value Measurements and Disclosures ), resulting in some volatility in earnings each period.
Income Tax	INCOME TAX in the consolidated statements of income includes deferred income tax provisions or benefits for all significant temporary differences in recognizing income and expenses for financial reporting and income tax purposes. The Corporation files consolidated income tax returns with its subsidiaries. The Corporation is generally no longer subject to U.S. federal, state and local income tax examinations by tax authorities for tax years before 2014 . The Corporation adopted the provisions of the ASC 740, Income Taxes , which prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. ASC 740 also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition. As a result of the implementation of ASC 740, the Corporation did not identify any uncertain tax positions that it believes should be recognized in the financial statements. The Corporation's policy is to recognize interest and penalties related to unrecognized tax benefits, if any, as a component of income tax expense.
Stock Option and Restricted Stock Award Plans	STOCK OPTION AND RESTRICTED STOCK AWARD PLANS are maintained by the Corporation. The compensation costs are recognized for stock options and restricted stock awards issued to employees and directors based on the fair value of these awards at the date of grant. A Black-Scholes model is utilized to estimate the fair value of stock options. The market price of the Corporation’s common stock at the date of grant is used for restricted stock awards. Compensation expense is recognized over the appropriate service period, which is generally two or three years.
Transfers of Financial Assets	TRANSFERS OF FINANCIAL ASSETS are accounted for as sales, when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Corporation and put presumptively beyond the reach of the transferor and its creditors, even in bankruptcy or other receivership, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets and (3) the Corporation does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity or the ability to unilaterally cause the holder to return specific assets.
Net Income Per Share	NET INCOME PER SHARE is computed by dividing net income available to common shareholders by the weighted-average number of shares of common stock outstanding. Diluted net income per share is computed by dividing net income available to common shareholders by the weighted-average number of shares of common stock outstanding, plus the dilutive effect of outstanding stock options and nonvested restricted stock.
Reclassifications	RECLASSIFICATIONS have been made to prior financial statements to conform to the current financial statement presentation. These reclassifications had no effect on net income.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Preliminary Valuations of the Fair Value of Assets Acquired and Liabilities Assumed	Fair Value Cash and cash equivalents $ 6,016 Interest-bearing time deposits 248,212 Investment securities 4,078 Loans held for sale 594 Loans 725,382 Premises and equipment 10,107 Federal Home Loan Bank stock 4,810 Interest receivable 3,445 Cash surrender value of life insurance 26,964 Other assets 11,780 Deposits (862,271 ) Securities sold under repurchase agreements (17,915 ) Federal Home Loan Bank Advances (47,575 ) Subordinated debentures (10,583 ) Interest payable (1,005 ) Other liabilities (14,472 ) Net tangible assets acquired 87,567 Other Intangible assets 17,403 Goodwill 153,636 Purchase price $ 258,606 Fair Value Cash and cash equivalents $ 48,532 Interest-bearing time deposits 292 Loans held for sale 7,626 Loans 224,680 Premises and equipment 1,986 Federal Home Loan Bank stock 1,091 Interest receivable 653 Other assets 1,620 Deposits (252,783 ) Interest payable (244 ) Other liabilities (3,106 ) Net tangible assets acquired 30,347 Core deposit intangible 4,526 Goodwill 47,719 Purchase price $ 82,592
Schedule of Acquired Loan Data	Acquired loan data for Arlington Bank can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 2,625 $ 6,183 $ 2,891 Acquired receivables not subject to ASC 310-30 $ 222,055 $ 308,857 $ 2,741 Acquired loan data for IAB can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 4,838 $ 14,131 $ 8,352 Acquired receivables not subject to ASC 310-30 $ 720,544 $ 864,613 $ 9,786 The following table presents loans acquired during the period ending December 31, 2017, for which it was probable at acquisition that all contractually required payments would not be collected. There were no loans acquired during the period ending December 31, 2016. 2017 IAB Arlington Bank Total Contractually required payments receivable at acquisition date $ 14,131 $ 6,183 $ 20,314 Nonaccretable difference 8,352 2,891 11,243 Expected cash flows at acquisition date 5,779 3,292 9,071 Accretable difference 941 667 1,608 Basis in loans at acquisition date $ 4,838 $ 2,625 $ 7,463
Schedule of Pro Forma Information from Acquisition	The following schedule includes pro forma results for the year ended December 31, 2017 and 2016 , as if the Arlington Bank and IAB acquisitions occurred as of the beginning of the periods presented. 2017 2016 Total revenue (net interest income plus other income) $ 380,324 $ 353,732 Net income $ 95,009 $ 95,288 Net income available to common shareholders Earnings per share: Basic $ 1.94 $ 1.95 Diluted $ 1.93 $ 1.94

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Approximate Market Value of Securities	The amortized cost, gross unrealized gains, gross unrealized losses and approximate market value of the Corporation's investment securities at the dates indicated were: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available for sale at December 31, 2017 State and municipal $ 510,852 $ 16,932 $ 1,091 $ 526,693 U.S. Government-sponsored mortgage-backed securities 473,325 964 3,423 470,866 Corporate obligations 31 31 Equity securities 2,357 2,357 Total available for sale 986,565 17,896 4,514 999,947 Held to maturity at December 31, 2017 U.S. Government-sponsored agency securities 22,618 435 22,183 State and municipal 235,594 6,295 244 241,645 U.S. Government-sponsored mortgage-backed securities 301,443 3,341 1,404 303,380 Foreign Investment 1,000 1,000 Total held to maturity 560,655 9,636 2,083 568,208 Total Investment Securities $ 1,547,220 $ 27,532 $ 6,597 $ 1,568,155 Available for sale at December 31, 2016 U.S. Government-sponsored agency securities $ 100 $ 100 State and municipal 360,779 $ 8,443 $ 5,564 363,658 U.S. Government-sponsored mortgage-backed securities 313,459 1,904 3,071 312,292 Corporate obligations 31 31 Equity securities 21,820 1,039 20,781 Total available for sale 696,189 10,347 9,674 696,862 Held to maturity at December 31, 2016 U.S. Government-sponsored agency securities 22,619 479 22,140 State and municipal 224,811 3,136 1,796 226,151 U.S. Government-sponsored mortgage-backed securities 360,213 4,956 1,527 363,642 Total held to maturity 607,643 8,092 3,802 611,933 Total Investment Securities $ 1,303,832 $ 18,439 $ 13,476 $ 1,308,795
Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position	The following table shows the Corporation’s gross unrealized losses and fair value, aggregated by investment category and length of time the individual securities have been in a continuous unrealized loss position at December 31, 2017 and 2016 : Less than 12 Months 12 Months or Longer Total Fair Gross Fair Gross Fair Gross Temporarily Impaired Available for Sale Securities at December 31, 2017 State and municipal $ 13,296 $ 198 $ 35,324 $ 893 $ 48,620 $ 1,091 U.S. Government-sponsored mortgage-backed securities 182,755 1,520 68,667 1,903 251,422 3,423 Total Temporarily Impaired Available for Sale Securities 196,051 1,718 103,991 2,796 300,042 4,514 Temporarily Impaired Held to Maturity Securities at December 31, 2017 U.S. Government-sponsored agency securities 9,988 131 12,196 304 22,184 435 State and municipal 2,430 36 15,805 208 18,235 244 U.S. Government-sponsored mortgage-backed securities 62,508 485 43,078 919 105,586 1,404 Total Temporarily Impaired Held to Maturity Securities 74,926 652 71,079 1,431 146,005 2,083 Total Temporarily Impaired Investment Securities $ 270,977 $ 2,370 $ 175,070 $ 4,227 $ 446,047 $ 6,597 Less than 12 Months 12 Months or Longer Total Fair Gross Fair Gross Fair Gross Temporarily Impaired Available for Sale Securities at December 31, 2016 State and municipal $ 126,593 $ 5,564 $ 126,593 $ 5,564 U.S. Government-sponsored mortgage-backed securities 185,544 3,071 185,544 3,071 Equity securities 18,765 1,039 18,765 1,039 Total Temporarily Impaired Available for Sale Securities 330,902 9,674 330,902 9,674 Temporarily Impaired Held to Maturity Securities at December 31, 2016 U.S. Government-sponsored agency securities 19,121 479 19,121 479 State and municipal 50,897 1,796 50,897 1,796 U.S. Government-sponsored mortgage-backed securities 109,377 1,527 109,377 1,527 Total Temporarily Impaired Held to Maturity Securities 179,395 3,802 179,395 3,802 Total Temporarily Impaired Investment Securities $ 510,297 $ 13,476 $ 510,297 $ 13,476
Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity	Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Available for Sale Held to Maturity Amortized Cost Fair Value Amortized Cost Fair Value Maturity Distribution at December 31, 2017 Due in one year or less $ 425 $ 425 $ 12,015 $ 12,158 Due after one through five years 5,040 5,204 76,146 76,334 Due after five through ten years 74,921 78,806 54,441 55,679 Due after ten years 430,497 442,289 116,610 120,657 510,883 526,724 259,212 264,828 U.S. Government-sponsored mortgage-backed securities 473,325 470,866 301,443 303,380 Equity securities 2,357 2,357 Total Investment Securities $ 986,565 $ 999,947 $ 560,655 $ 568,208

Loans and Allowance (Tables)

Loans and Allowance (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Composition of Loan Portfolio by Loan Class	The following table illustrates the composition of the Corporation’s loan portfolio by loan class for the years indicated: December 31, 2017 December 31, 2016 Commercial and industrial loans $ 1,493,493 $ 1,194,646 Agricultural production financing and other loans to farmers 121,757 79,689 Real estate loans: Construction 612,219 418,703 Commercial and farmland 2,562,691 1,953,062 Residential 962,765 739,169 Home equity 514,021 418,525 Individuals' loans for household and other personal expenditures 86,935 77,479 Lease financing receivables, net of unearned income 2,527 311 Other commercial loans 394,791 258,061 Loans 6,751,199 5,139,645 Allowance for loan losses (75,032 ) (66,037 ) Net Loans $ 6,676,167 $ 5,073,608
Changes in Allowance for Loan Losses	The following tables summarize changes in the allowance for loan losses by loan segment for the twelve months ended December 31, 2017, 2016, and 2015: Twelve Months Ended December 31, 2017 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2016 $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Provision for losses 2,515 3,159 1,078 2,391 9,143 Recoveries on loans 1,590 2,260 324 706 4,880 Loans charged off (1,383 ) (1,737 ) (593 ) (1,315 ) (5,028 ) Balances, December 31, 2017 $ 30,418 $ 27,343 $ 3,732 $ 13,537 $ 2 $ 75,032 Twelve Months Ended December 31, 2016 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2015 $ 26,478 $ 22,145 $ 2,689 $ 11,139 $ 2 $ 62,453 Provision for losses 1,876 1,834 432 1,515 5,657 Recoveries on loans 1,806 2,090 369 1,091 5,356 Loans charged off (2,464 ) (2,408 ) (567 ) (1,990 ) (7,429 ) Balances, December 31, 2016 $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Twelve Months Ended December 31, 2015 Commercial Commercial Real Estate Consumer Residential Finance Total Allowance for loan losses: Balances, December 31, 2014 $ 28,824 $ 19,327 $ 2,658 $ 13,152 $ 3 $ 63,964 Provision for losses (1,901 ) 1,710 299 310 $ (1 ) 417 Recoveries on loans 1,911 2,545 352 1,536 6,344 Loans charged off (2,356 ) (1,437 ) (620 ) (3,859 ) (8,272 ) Balances, December 31, 2015 $ 26,478 $ 22,145 $ 2,689 $ 11,139 $ 2 $ 62,453
Allowance for Credit Losses and Loan Portfolio by Loan Segment	The following tables show the Corporation’s allowance for loan losses and loan portfolio by loan segment for the years indicated: December 31, 2017 Commercial Commercial Consumer Residential Finance Total Allowance balances: Individually evaluated for impairment $ 666 $ 567 $ 404 $ 1,637 Collectively evaluated for impairment 29,752 26,776 $ 3,732 13,133 $ 2 73,395 Total Allowance for Loan Losses $ 30,418 $ 27,343 $ 3,732 $ 13,537 $ 2 $ 75,032 Loan balances: Individually evaluated for impairment $ 4,776 $ 21,009 $ 5 $ 3,941 $ 29,731 Collectively evaluated for impairment 2,003,844 3,131,589 86,930 1,471,309 $ 2,527 6,696,199 Loans acquired with deteriorated credit quality 1,421 22,312 1,536 25,269 Loans $ 2,010,041 $ 3,174,910 $ 86,935 $ 1,476,786 $ 2,527 $ 6,751,199 December 31, 2016 Commercial Commercial Consumer Residential Finance Total Allowance balances: Individually evaluated for impairment $ 37 $ 553 $ 298 $ 888 Collectively evaluated for impairment 27,659 23,108 $ 2,923 11,457 $ 2 65,149 Total Allowance for Loan Losses $ 27,696 $ 23,661 $ 2,923 $ 11,755 $ 2 $ 66,037 Loan balances: Individually evaluated for impairment $ 4,762 $ 21,358 $ 9 $ 4,450 $ 30,579 Collectively evaluated for impairment 1,520,981 2,315,686 77,470 1,151,396 $ 311 5,065,844 Loans acquired with deteriorated credit quality 6,653 34,721 1,848 43,222 Loans $ 1,532,396 $ 2,371,765 $ 77,479 $ 1,157,694 $ 311 $ 5,139,645
Summary of Non-Accrual Loans by Loan class	The following table summarizes the Corporation’s non-accrual loans by loan class for the years indicated: December 31, 2017 December 31, 2016 Commercial and industrial loans $ 3,275 $ 1,839 Agriculture production financing and other loans to farmers 1,027 1,329 Real estate loans: Construction 65 73 Commercial and farmland 12,951 15,754 Residential 9,444 9,523 Home equity 1,928 1,457 Individuals' loans for household and other personal expenditures 34 23 Total $ 28,724 $ 29,998
Composition of Impaired Loans by Loan Class	The following tables show the composition of the Corporation’s commercial impaired loans, related allowance and interest income recognized while impaired by loan class for the years indicated: December 31, 2017 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 14,110 $ 3,850 $ 7,653 $ 186 Agriculture production financing and other loans to farmers 1,595 1,238 1,304 20 Real estate loans: Construction 2,530 1,396 1,420 64 Commercial and farmland 51,829 39,651 43,445 1,734 Residential 5,403 3,133 3,558 122 Home equity 80 40 48 Total $ 75,547 $ 49,308 $ 57,428 $ 2,126 Impaired loans with related allowance: Commercial and industrial loans $ 812 $ 782 $ 552 $ 1,517 Agriculture production financing and other loans to farmers 357 327 114 327 Real estate loans: Commercial and farmland 2,989 2,270 567 2,383 $ 4 Total $ 4,158 $ 3,379 $ 1,233 $ 4,227 $ 4 Total Impaired Loans $ 79,705 $ 52,687 $ 1,233 $ 61,655 $ 2,130 December 31, 2016 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 17,645 $ 10,074 $ 13,393 $ 499 Agriculture production financing and other loans to farmers 757 680 750 3 Real estate loans: Construction 5,946 3,178 3,255 258 Commercial and farmland 67,936 49,731 51,740 2,978 Residential 8,039 4,664 5,410 167 Home equity 82 44 44 Other commercial loans 11 Total $ 100,416 $ 68,371 $ 74,592 $ 3,905 Impaired loans with related allowance: Agriculture production financing and other loans to farmers $ 660 $ 660 $ 36 $ 691 Real estate loans: Commercial and farmland 4,238 2,985 553 2,989 Residential 65 34 23 38 Total $ 4,963 $ 3,679 $ 612 $ 3,718 Total Impaired Loans $ 105,379 $ 72,050 $ 612 $ 78,310 $ 3,905 December 31, 2015 Unpaid Principal Recorded Related Average Recorded Investment Interest Income Recognized Impaired loans with no related allowance: Commercial and industrial loans $ 22,151 $ 11,669 $ 12,578 $ 488 Agriculture production financing and other loans to farmers 370 361 439 Real estate loans: Construction 4,551 2,336 3,662 157 Commercial and farmland 95,930 69,024 71,569 3,328 Residential 11,262 7,338 7,926 244 Home equity 297 247 249 Other commercial loans 20 Total $ 134,581 $ 90,975 $ 96,423 $ 4,217 Impaired loans with related allowance: Commercial and industrial loans $ 3,043 $ 2,690 $ 1,247 $ 2,752 $ 38 Agriculture production financing and other loans to farmers 466 466 30 538 Real estate loans: Commercial and farmland 2,144 1,933 392 1,868 Residential 2,300 1,463 173 1,787 Total $ 7,953 $ 6,552 $ 1,842 $ 6,945 $ 38 Total Impaired Loans $ 142,534 $ 97,527 $ 1,842 $ 103,368 $ 4,255
Credit Quality of Loan Portfolio by Loan Class	The following tables summarize the credit quality of the Corporation’s loan portfolio, by loan class for the years indicated. Consumer non-performing loans include accruing consumer loans 90 plus days delinquent and consumer non-accrual loans. The entire balance of a loan is considered delinquent if the minimum payment contractually required to be made is not received by the specified date. Loans that evidenced deterioration of credit quality since origination and it was probable, at acquisition, that all contractually required payments would not be collected are included in the applicable categories below. December 31, 2017 Commercial Pass Commercial Special Mention Commercial Substandard Commercial Doubtful Commercial Loss Consumer Performing Consumer Total Commercial and industrial loans $ 1,418,401 $ 51,336 $ 23,386 $ 370 $ 1,493,493 Agriculture production financing and other loans to farmers 73,800 27,502 20,018 387 $ 50 121,757 Real estate loans: Construction 587,906 828 981 $ 22,374 $ 130 612,219 Commercial and farmland 2,408,329 70,074 79,769 1,536 2,980 3 2,562,691 Residential 185,725 4,376 4,209 114 759,900 8,441 962,765 Home equity 28,554 457 286 482,661 2,063 514,021 Individuals' loans for household and other personal expenditures 86,875 60 86,935 Lease financing receivables, net of unearned income 2,527 2,527 Other commercial loans 394,222 569 394,791 Loans $ 5,099,464 $ 154,573 $ 129,218 $ 2,407 $ 50 $ 1,354,790 $ 10,697 $ 6,751,199 December 31, 2016 Commercial Pass Commercial Special Mention Commercial Substandard Commercial Doubtful Commercial Loss Consumer Performing Consumer Total Commercial and industrial loans $ 1,117,545 $ 30,919 $ 46,182 $ 1,194,646 Agriculture production financing and other loans to farmers 30,712 25,273 23,704 79,689 Real estate loans: Construction 398,646 3,490 1,858 $ 14,636 $ 73 418,703 Commercial and farmland 1,811,367 60,028 80,626 1,034 7 1,953,062 Residential 146,251 5,106 6,046 574,054 7,712 739,169 Home equity 7,310 47 516 409,237 1,415 418,525 Individuals' loans for household and other personal expenditures 77,456 23 77,479 Lease financing receivables, net of unearned income 228 83 311 Other commercial loans 257,861 200 258,061 Loans $ 3,769,920 $ 124,863 $ 159,215 $ 1,076,417 $ 9,230 $ 5,139,645
Past Due Aging of Loan Portfolio by Loan Class	The tables below show a past due aging of the Corporation’s loan portfolio, by loan class, for the years indicated: December 31, 2017 Current 30-59 Days 60-89 Days Loans > 90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,487,221 $ 2,967 $ 30 $ 3,275 $ 6,272 $ 1,493,493 Agriculture production financing and other loans to farmers 120,720 10 1,027 1,037 121,757 Real estate loans: Construction 610,896 1,193 $ 65 65 1,323 612,219 Commercial and farmland 2,542,048 6,923 166 603 12,951 20,643 2,562,691 Residential 948,947 4,010 308 56 9,444 13,818 962,765 Home equity 510,362 1,372 184 175 1,928 3,659 514,021 Individuals' loans for household and other personal expenditures 85,744 298 834 25 34 1,191 86,935 Lease financing receivables, net of unearned income 2,527 2,527 Other commercial loans 394,791 394,791 Loans $ 6,703,256 $ 16,773 $ 1,522 $ 924 $ 28,724 $ 47,943 $ 6,751,199 December 31, 2016 Current 30-59 Days 60-89 Days Loans > 90 Days Non-Accrual Total Past Due Total Commercial and industrial loans $ 1,192,079 $ 466 $ 162 $ 100 $ 1,839 $ 2,567 $ 1,194,646 Agriculture production financing and other loans to farmers 78,360 1,329 1,329 79,689 Real estate loans: Construction 415,975 2,655 73 2,728 418,703 Commercial and farmland 1,932,896 1,385 3,027 15,754 20,166 1,953,062 Residential 725,338 3,664 635 9 9,523 13,831 739,169 Home equity 415,969 850 246 3 1,457 2,556 418,525 Individuals' loans for household and other personal expenditures 76,929 470 57 23 550 77,479 Lease financing receivables, net of unearned income 311 311 Other commercial loans 258,061 258,061 Loans $ 5,095,918 $ 9,490 $ 4,127 $ 112 $ 29,998 $ 43,727 $ 5,139,645
Schedules of Troubled Debt Restructuring	The following tables summarize the recorded investment of troubled debt restructures as of December 31, 2017 and 2016 , by modification type, that occurred during the years indicated: December 31, 2017 Term Rate Combination Total Commercial and industrial loans $ 203 $ 166 $ 369 Agriculture production financing and other farm loans 387 387 Real estate loans: Commercial and farmland 705 $ 59 232 996 Residential 761 85 846 Home equity 105 105 Individuals' loans for household and other personal expenditures 14 14 Total $ 1,295 $ 939 $ 483 $ 2,717 December 31, 2016 Term Rate Combination Total Commercial and industrial loans $ 397 $ 397 Agriculture production financing and other loans to farmers $ 660 $ 12 672 Real estate loans: Commercial and farmland 297 3,456 3,753 Residential 238 928 1,166 Home equity 266 266 Individuals' loans for household and other personal expenditures 9 9 Total $ 1,195 $ 1,215 $ 3,853 $ 6,263 The following tables summarize troubled debt restructures that occurred during the twelve months ended December 31, 2017 and 2016 , that subsequently defaulted during the period indicated and remained in default at period end. For purposes of this schedule, a loan is considered in default if it is 30 or more days past due. Twelve Months Ended December 31, 2017 Number of Loans Recorded Balance Real estate loans: Commercial and farmland 1 $ 14 Residential 4 323 Total 5 $ 337 Twelve Months Ended December 31, 2016 Number of Loans Recorded Balance Commercial and industrial loans 3 $ 197 Agriculture production financing and other loans to farmers 1 661 Real estate loans: Commercial and farmland 1 343 Residential 1 $ 64 Total 6 $ 1,265 The following tables summarize troubled debt restructures in the Corporation's loan portfolio that occurred during the periods ended December 31, 2017 and 2016 : December 31, 2017 Pre-Modification Post-Modification Number Commercial and industrial loans $ 599 $ 376 3 Agriculture production financing and other loans to farmers 387 387 3 Real estate loans: Commercial and farmland 1,022 1,156 8 Residential 788 862 15 Home equity 195 107 4 Individuals' loans for household and other personal expenditures 13 14 1 Total $ 3,004 $ 2,902 34 December 31, 2016 Pre-Modification Post-Modification Number Commercial and industrial loans $ 410 $ 410 4 Agriculture production financing and other loans to farmers 1,368 1,234 4 Real estate loans: Commercial and farmland 3,978 3,954 7 Residential 1,126 1,183 17 Home equity 266 244 4 Individuals' loans for household and other personal expenditures 17 10 1 Total $ 7,165 $ 7,035 37

Accounting for Certain Loans 40

Accounting for Certain Loans Acquired in a Purchase (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Schedule of Outstanding Balance and Carrying Amount of Acquired Loans	The following tables include the outstanding balance and carrying amount of all acquired loans which were included in the Corporation's balance sheet at December 31, 2017 and December 31, 2016. December 31, 2017 IAB Arlington Bank Ameriana C Financial Community CFS SCB Total Outstanding Balance: Commercial and industrial loans $ 83,630 $ 3,152 $ 4,150 $ 64 $ 235 $ 10,539 $ 1,760 $ 103,530 Agricultural production financing and other loans to farmers 33,537 76 50 1,317 34,980 Real estate loans: Construction 23,571 14,716 2,451 830 1,499 65 43,132 Commercial and farmland 346,155 76,375 79,739 15,791 27,910 65,578 6,733 618,281 Residential 100,569 69,011 86,098 32,854 6,354 79,674 2,899 377,459 Home equity 36,349 22,581 8,800 5,733 4,392 19,972 9,636 107,463 Individuals' loans for household and other personal expenditures 3,552 174 356 82 22 21 4,207 Other commercial loans 11,189 90 1,745 58 13,082 Total 638,552 186,099 183,339 55,272 40,548 175,958 22,366 1,302,134 Remaining fair value discount (20,090 ) (5,242 ) (6,689 ) (1,266 ) (2,482 ) (5,859 ) (2,120 ) (43,748 ) Carrying amount 618,462 180,857 176,650 54,006 38,066 170,099 20,246 1,258,386 Allowance 290 411 52 16 769 Carrying amount net of allowance $ 618,172 $ 180,857 $ 176,239 $ 54,006 $ 38,014 $ 170,083 $ 20,246 $ 1,257,617 December 31, 2016 Ameriana C Financial Community CFS SCB Total Outstanding Balance: Commercial and industrial loans $ 8,003 $ 85 $ 2,269 $ 23,327 $ 3,552 $ 37,236 Agricultural production financing and other loans to farmers 1,030 50 1,630 2,710 Real estate loans: Construction 22,017 2,835 4,026 420 29,298 Commercial and farmland 103,075 22,130 36,947 131,895 9,315 303,362 Residential 103,414 44,101 9,363 96,627 4,135 257,640 Home Equity 11,728 7,947 6,326 26,894 11,924 64,819 Individuals' loans for household and other personal expenditures 762 2 147 201 30 1,142 Other commercial loans 1,825 65 1,890 Total 250,824 77,100 60,108 279,479 30,586 698,097 Remaining fair value discount (10,771 ) (1,906 ) (4,101 ) (12,634 ) (3,268 ) (32,680 ) Carrying Amount 240,053 75,194 56,007 266,845 27,318 665,417 Allowance 265 23 92 380 Carrying Amount Net of Allowance $ 239,788 $ 75,194 $ 55,984 $ 266,753 $ 27,318 $ 665,037
Schedule of Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement	The accretable portion, or income expected to be collected, and reclassifications from nonaccretable, are identified in the tables below for the years indicated. Twelve Months Ended December 31, 2017 IAB Arlington Bank Ameriana C Financial Community CFS SCB Total Beginning balance $ 1,629 $ 73 $ 1,233 $ 736 $ 279 $ 3,950 Additions $ 941 $ 667 1,608 Accretion (1,009 ) (314 ) (2,983 ) (260 ) (454 ) (1,172 ) (557 ) (6,749 ) Reclassification from nonaccretable 834 164 1,805 187 212 1,075 471 4,748 Disposals (122 ) (545 ) (667 ) Ending balance $ 766 $ 517 $ 451 $ 869 $ 94 $ 193 $ 2,890 Twelve Months Ended December 31, 2016 Ameriana C Financial Community CFS SCB Total Beginning balance $ 2,160 $ 114 $ 1,508 $ 1,188 $ 642 $ 5,612 Additions Accretion (311 ) (123 ) (1,119 ) (4,268 ) (756 ) (6,577 ) Reclassification from nonaccretable 12 82 858 3,827 393 5,172 Disposals (232 ) (14 ) (11 ) (257 ) Ending balance $ 1,629 $ 73 $ 1,233 $ 736 $ 279 $ 3,950 Twelve Months Ended December 31, 2015 Ameriana C Financial Community CFS SCB Total Beginning balance $ 2,122 $ 2,400 $ 868 $ 5,390 Additions $ 2,160 $ 145 2,305 Accretion (31 ) (723 ) (4,050 ) (1,046 ) (5,850 ) Reclassification from nonaccretable 249 2,854 822 3,925 Disposals (140 ) (16 ) (2 ) (158 ) Ending balance $ 2,160 $ 114 $ 1,508 $ 1,188 $ 642 $ 5,612
Schedule of Loans Acquired for which Contractually Required Payments would not be Collected	Acquired loan data for Arlington Bank can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 2,625 $ 6,183 $ 2,891 Acquired receivables not subject to ASC 310-30 $ 222,055 $ 308,857 $ 2,741 Acquired loan data for IAB can be found in the table below: Fair Value of Acquired Loans at Acquisition Date Gross Contractual Amounts Receivable at Acquisition Date Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected Acquired receivables subject to ASC 310-30 $ 4,838 $ 14,131 $ 8,352 Acquired receivables not subject to ASC 310-30 $ 720,544 $ 864,613 $ 9,786 The following table presents loans acquired during the period ending December 31, 2017, for which it was probable at acquisition that all contractually required payments would not be collected. There were no loans acquired during the period ending December 31, 2016. 2017 IAB Arlington Bank Total Contractually required payments receivable at acquisition date $ 14,131 $ 6,183 $ 20,314 Nonaccretable difference 8,352 2,891 11,243 Expected cash flows at acquisition date 5,779 3,292 9,071 Accretable difference 941 667 1,608 Basis in loans at acquisition date $ 4,838 $ 2,625 $ 7,463

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Premises and Equipment	The following table summarizes the Corporation's premises and equipment as of December 31, 2017 and 2016 : 2017 2016 Cost at December 31: Land $ 22,042 $ 25,035 Buildings and Leasehold Improvements 124,441 114,444 Equipment 82,344 65,547 Total Cost 228,827 205,026 Accumulated Depreciation and Amortization (132,975 ) (110,594 ) Net $ 95,852 $ 94,432
Schedule of Future Minimum Rental Payments for Operating Leases	The future minimum rental commitments required under the operating leases, which expire at various dates through the year 2035, are as follows for the years ending December 31: Future Minimum Rental Commitments 2018 $ 3,161 2019 3,611 2020 3,484 2021 3,137 2022 3,090 After 2022 15,180 Total Future Minimum Obligations $ 31,663

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	2017 2016 Balance, January 1 $ 244,000 $ 243,129 Goodwill acquired 201,824 Measurement period adjustment (469 ) $ 871 Balance, December 31 $ 445,355 $ 244,000

Other Intangibles (Tables)

Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Core Deposit and Other Intangibles	The carrying basis and accumulated amortization of recognized core deposit and other intangibles are noted below. 2017 2016 Gross carrying amount $ 63,940 $ 61,798 Core deposit intangible acquired 18,164 Other intangibles acquired 3,765 Measurement period adjustment 2,142 Accumulated amortization (54,721 ) (49,074 ) Core deposit intangible and other intangibles reduction Core Deposit and Other Intangibles $ 31,148 $ 14,866
Schedule of Estimated Future Amortization Expense	Estimated future amortization expense is summarized as follows: Amortization Expense 2018 $ 6,719 2019 5,169 2020 3,632 2021 3,427 2022 3,325 After 2022 8,876 $ 31,148

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of Deposits	The composition of the deposit portfolio is included in the table below for the years indicated: December 31, 2017 December 31, 2016 Demand deposits $ 3,746,654 $ 2,866,853 Savings deposits 1,994,366 1,560,752 Certificates and other time deposits of $100,000 or more 468,895 276,274 Other certificates and time deposits 581,894 471,247 Brokered deposits 380,721 381,372 Total deposits $ 7,172,530 $ 5,556,498
Summary of Contractual Maturities of Time Deposits	At December 31, 2017 , the contractual maturities of time deposits are summarized as follows: Certificates and Other Time Deposits 2018 $ 876,126 2019 330,892 2020 119,066 2021 63,005 2022 27,518 After 2022 14,903 $ 1,431,510

Transfers Accounted for as Se45

Transfers Accounted for as Secured Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of Collateral Pledged for all Repurchase Agreements Accounted for as Secured Borrowings	The collateral pledged for all repurchase agreements that are accounted for as secured borrowings as of December 31, 2017 and 2016 were: December 31, 2017 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater Than 90 Days Total U.S. Government-sponsored mortgage-backed securities $ 126,187 1,340 1,500 $ 7,596 $ 136,623 December 31, 2016 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater Than 90 Days Total U.S. Government-sponsored mortgage-backed securities $ 129,617 1,337 10,253 $ 5,273 $ 146,480

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes the Corporation's borrowings as of December 31, 2017 and 2016: December 31, 2017 December 31, 2016 Federal funds purchased $ 144,038 $ 120,349 Securities sold under repurchase agreements 136,623 146,480 Federal Home Loan Bank advances 414,377 298,923 Subordinated debentures and term loans 139,349 128,445 Total Borrowings $ 834,387 $ 694,197
Schedule of Maturities of Long-term Debt	Contractual maturities of borrowings as of December 31, 2017 , are as follows: Maturities in Years Ending December 31: Federal Funds Purchased Securities Sold Federal Home Subordinated 2018 $ 144,038 $ 136,623 $ 171,391 2019 121,713 2020 41,273 2021 25,000 2022 20,000 After 2022 35,000 $ 143,430 ASC 805 fair value adjustments at acquisition (4,081 ) $ 144,038 $ 136,623 $ 414,377 $ 139,349

Derivative Instruments and He47

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivative Financial Instruments and Classification on the Balance Sheet	The table below presents the fair value of the Corporation’s derivative financial instruments as well as their classification on the Balance Sheet as of December 31, 2017 and December 31, 2016 . Asset Derivatives Liability Derivatives December 31, 2017 December 31, 2016 December 31, 2017 December 31, 2016 Balance Sheet Location Fair Balance Sheet Location Fair Balance Sheet Location Fair Balance Sheet Location Fair Derivatives designated as hedging instruments: Interest rate contracts Other Assets $ 18 Other Assets $ 15 Other Liabilities $ 1,383 Other Liabilities $ 2,182 Derivatives not designated as hedging instruments: Interest rate contracts Other Assets $ 7,305 Other Assets $ 6,295 Other Liabilities $ 7,305 Other Liabilities $ 6,295
Amount of Gain (Loss) Recognized in Other Comprehensive Income	The amount of gain (loss) recognized in other comprehensive income is included in the table below for the periods indicated. Derivatives in Cash Flow Hedging Relationships Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivative 2017 2016 Interest rate products $ 13 $ (368 )
Effect of Derivative Financial Instruments on the Income Statement	The tables below present the effect of the Corporation’s derivative financial instruments on the Income Statement for the years ended December 31, 2017 , 2016 and 2015 . Derivatives Not Location of Gain Amount of Gain (Loss) Recognized in Income on Derivative 2017 2016 2015 Interest rate contracts Other income $ — $ 211 $ (53 ) Derivatives Designated as Hedging Location of Loss Reclassified from Accumulated Other Comprehensive Income (Effective Portion) Amount of Loss Reclassified from Other Comprehensive Income into Income (Effective Portion) 2017 2016 2015 Interest rate contracts Interest expense $ (985 ) $ (1,250 ) $ (1,427 )

Fair Values of Financial Inst48

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements of Assets and Liabilities Recognized in the Balance Sheets Measured at Fair Value on Recurring Basis	The following table presents the fair value measurements of assets and liabilities recognized in the accompanying balance sheets measured at fair value on a recurring basis and the level within the ASC 820-10 fair value hierarchy in which the fair value measurements fall at December 31, 2017 and 2016 . Fair Value Measurements Using: Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Available for sale securities: State and municipal $ 526,693 $ 522,750 $ 3,943 U.S. Government-sponsored mortgage-backed securities 470,866 470,866 Corporate obligations 31 31 Equity securities 2,357 2,353 4 Interest rate swap asset 7,305 7,305 Interest rate cap 18 18 Interest rate swap liability 8,688 8,688 Fair Value Measurements Using: Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Available for sale securities: U.S. Government-sponsored agency securities $ 100 $ 100 State and municipal 363,658 358,524 $ 5,134 U.S. Government-sponsored mortgage-backed securities 312,292 312,292 Corporate obligations 31 31 Equity securities 20,781 $ 18,765 2,012 4 Interest rate swap asset 6,295 6,295 Interest rate cap 15 15 Interest rate swap liability 8,477 8,477
Reconciliation of Beginning and Ending Balances of Recurring Fair Value Measurements Recognized in the Balance Sheets using Significant Unobservable Level 3 Inputs	The following is a reconciliation of the beginning and ending balances of recurring fair value measurements recognized in the accompanying balance sheets using significant unobservable Level 3 inputs for year ended December 31, 2017 and 2016 . Available for Sale Securities For The Year Ended December 31, 2017 December 31, 2016 Beginning Balance $ 5,169 $ 5,932 Included in other comprehensive income 26 (223 ) Principal payments (1,217 ) (540 ) Ending balance $ 3,978 $ 5,169
Description of Valuation Methodologies Used for Instruments Measured at Fair Value on a Non-Recurring Basis and Recognized in the Balance Sheets	Following is a description of valuation methodologies used for instruments measured at fair value on a non-recurring basis and recognized in the accompanying balance sheets, as well as the general classification of such instruments pursuant to the valuation hierarchy for year ended December 31, 2017 and 2016 . Fair Value Measurements Using Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Impaired Loans (collateral dependent) $ 9,576 $ 9,576 Other real estate owned $ 859 $ 859 Fair Value Measurements Using Quoted Prices in Active Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Impaired Loans (collateral dependent) $ 15,318 $ 15,318 Other real estate owned $ 1,612 $ 1,612
Unobservable Inputs Used in Recurring and Nonrecurring Level 3 Fair Value Measurements Other than Goodwill	The following table presents quantitative information about unobservable inputs used in recurring and nonrecurring Level 3 fair value measurements, other than goodwill, at December 31, 2017 and 2016 . December 31, 2017 Fair Value Valuation Technique Unobservable Inputs Range (Weighted-Average) State and municipal securities $ 3,943 Discounted cash flow Maturity Call Date 1 month to 20 years Corporate obligations and Equity securities $ 35 Discounted cash flow Risk free rate 3 month LIBOR Impaired loans (collateral dependent) $ 9,576 Collateral based measurements Discount to reflect current market conditions and ultimate collectability 0% - 10% (1%) Other real estate owned $ 859 Appraisals Discount to reflect current market conditions 0% - 10% (2%) December 31, 2016 Fair Value Valuation Technique Unobservable Inputs Range (Weighted-Average) State and municipal securities $ 5,134 Discounted cash flow Maturity Call Date 1 month to 20 years Corporate obligations and Equity securities $ 35 Discounted cash flow Risk free rate 3 month LIBOR Impaired loans (collateral dependent) $ 15,318 Collateral based measurements Discount to reflect current market conditions and ultimate collectability 0% - 10% (1%) Other real estate owned $ 1,612 Appraisals Discount to reflect current market conditions 0% - 10% (9%)
Estimated Fair Values of Financial Instruments	The following table presents estimated fair values of the Corporation's financial instruments and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2017 and 2016 . 2017 Carrying Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets at December 31: Cash and cash equivalents $ 154,905 $ 154,905 Interest-bearing time deposits 35,027 35,027 Investment securities available for sale 999,947 $ 995,969 $ 3,978 Investment securities held to maturity 560,655 556,305 11,903 Loans held for sale 7,216 7,216 Loans 6,676,167 6,534,877 Federal Home Loan Bank stock 23,825 23,825 Interest rate swap asset 7,323 7,323 Interest receivable 37,130 37,130 Liabilities at December 31: Deposits $ 7,172,530 $ 5,741,019 $ 1,406,526 Borrowings: Federal funds purchased 144,038 144,038 Securities sold under repurchase agreements 136,623 136,562 Federal Home Loan Bank advances 414,377 361,085 Subordinated debentures and term loans 139,349 120,085 Interest rate swap liability 8,688 8,688 Interest payable 4,390 4,390 2016 Carrying Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets at December 31: Cash and cash equivalents $ 127,927 $ 127,927 Interest-bearing time deposits 24,459 24,459 Investment securities available for sale 696,862 18,765 $ 672,928 $ 5,169 Investment securities held to maturity 607,643 597,246 14,687 Loans held for sale 2,929 2,929 Loans 5,073,608 4,933,552 Federal Home Loan Bank stock 17,964 17,964 Interest rate swap asset 6,310 6,310 Interest receivable 26,194 26,194 Liabilities at December 31: Deposits $ 5,556,498 $ 4,427,605 $ 1,111,491 Borrowings: Federal funds purchased 120,349 120,349 Securities sold under repurchase agreements 146,480 146,449 Federal Home Loan Bank advances 298,923 297,465 Subordinated debentures and term loans 128,445 105,930 Interest rate swap liability 8,477 8,477 Interest payable 3,110 3,110

Commitments and Contingent Li49

Commitments and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Financial Instruments which Contract Amount Represents Credit Risk	Financial instruments, whose contract amount represents credit risk as of December 31, were as follows: 2017 2016 Amounts of commitments: Loan commitments to extend credit $ 2,482,641 $ 2,057,878 Standby letters of credit $ 43,526 $ 46,010

Accumulated Other Comprehensi50

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax, as of December 31, 2017 and 2016 : Accumulated Other Comprehensive Income (Loss) Unrealized Gains (Losses) on Securities Available for Sale Unrealized Gains (Losses) on Cash Flow Hedges Unrealized Gains (Losses) on Defined Benefit Plans Total Balance at December 31, 2016 $ 1,035 $ (1,774 ) $ (12,842 ) $ (13,581 ) Other comprehensive income before reclassifications 9,645 9 2,686 12,340 Amounts reclassified from accumulated other comprehensive income (1,710 ) 640 (597 ) (1,667 ) Period change 7,935 649 2,089 10,673 Balance at December 31, 2017 $ 8,970 $ (1,125 ) $ (10,753 ) $ (2,908 ) Balance at December 31, 2015 $ 12,325 $ (2,347 ) $ (11,340 ) $ (1,362 ) Other comprehensive income before reclassifications (9,087 ) (240 ) (470 ) (9,797 ) Amounts reclassified from accumulated other comprehensive income (2,203 ) 813 (1,032 ) (2,422 ) Period change (11,290 ) 573 (1,502 ) (12,219 ) Balance at December 31, 2016 $ 1,035 $ (1,774 ) $ (12,842 ) $ (13,581 )
Reclassification out of Accumulated Other Comprehensive Income (Loss)	The following table presents the reclassification adjustments out of accumulated other comprehensive income (loss) that were included in net income in the Consolidated Condensed Statements of Income for the years ended December 31, 2017 , 2016 and 2015 : Amount Reclassified from Accumulated Other Comprehensive Income (Loss) For the Year Ended December 31, Details about Accumulated Other Comprehensive Income (Loss) Components 2017 2016 2015 Affected Line Item in the Statements of Income Unrealized gains (losses) on available for sale securities (1) Realized securities gains reclassified into income $ 2,631 $ 3,389 $ 2,670 Other income - net realized gains on sales of available for sale securities Related income tax expense (921 ) (1,186 ) (934 ) Income tax expense $ 1,710 $ 2,203 $ 1,736 Unrealized gains (losses) on cash flow hedges (2) Interest rate contracts $ (985 ) $ (1,250 ) $ (1,427 ) Interest expense - subordinated debentures and term loans Related income tax benefit 345 437 499 Income tax expense $ (640 ) $ (813 ) $ (928 ) Unrealized gains (losses) on defined benefit plans Amortization of net loss and prior service costs $ 806 $ 1,588 $ 305 Other expenses - salaries and employee benefits Related income tax benefit (expense) (209 ) (556 ) (107 ) Income tax expense $ 597 $ 1,032 $ 198 Total reclassifications for the period, net of tax $ 1,667 $ 2,422 1,006 (1) For additional detail related to unrealized gains (losses) on available for sale securities and related amounts reclassified from accumulated other comprehensive income see NOTE 4. INVESTMENT SECURITIES. (2) For additional detail related to unrealized gains (losses) on cash flow hedges and related amounts reclassified from accumulated other comprehensive income see NOTE 13. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES.

Regulatory Capital and Divide51

Regulatory Capital and Dividends (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of Actual and Required Capital Amounts and Ratios	The Corporation's and Bank's actual and required capital ratios as of December 31, 2017 and December 31, 2016 were as follows: Prompt Corrective Action Thresholds Actual Adequately Capitalized Well Capitalized December 31, 2017 Amount Ratio Amount Ratio Amount Ratio Total risk-based capital to risk-weighted assets First Merchants Corporation $ 1,048,757 13.69 % $ 612,848 8.00 % N/A N/A First Merchants Bank 1,016,355 13.17 617,477 8.00 $ 771,847 10.00 % Tier 1 capital to risk-weighted assets First Merchants Corporation $ 908,725 11.86 % $ 459,636 6.00 % N/A N/A First Merchants Bank 941,323 12.20 463,108 6.00 $ 617,477 8.00 % Common equity tier 1 capital to risk-weighted assets First Merchants Corporation $ 842,806 11.00 % $ 344,727 4.50 % N/A N/A First Merchants Bank 941,323 12.20 347,331 4.50 $ 501,700 6.50 % Tier 1 capital to average assets First Merchants Corporation $ 908,725 10.43 % $ 348,407 4.00 % N/A N/A First Merchants Bank 941,323 10.83 347,794 4.00 $ 434,742 5.00 % Prompt Corrective Action Thresholds Actual Adequately Capitalized Well Capitalized December 31, 2016 Amount Ratio Amount Ratio Amount Ratio Total risk-based capital to risk-weighted assets First Merchants Corporation $ 851,521 14.21 % $ 479,470 8.00 % N/A N/A First Merchants Bank 800,598 13.30 481,490 8.00 $ 601,862 10.00 % Tier 1 capital to risk-weighted assets First Merchants Corporation $ 720,484 12.02 % $ 359,603 6.00 % N/A N/A First Merchants Bank 734,561 12.20 361,117 6.00 $ 481,490 8.00 % Common equity tier 1 capital to risk-weighted assets First Merchants Corporation $ 665,445 11.10 % $ 269,702 4.50 % N/A N/A First Merchants Bank 734,561 12.20 270,838 4.50 $ 391,210 6.50 % Tier 1 capital to average assets First Merchants Corporation $ 720,484 10.54 % $ 273,456 4.00 % N/A N/A First Merchants Bank 734,561 10.78 272,461 4.00 $ 340,576 5.00 %

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Components of Share Based Compensation Awards	The following table summarizes the components of the Corporation's share-based compensation awards recorded as an expense and the income tax benefit of such awards. The income tax benefit increase for the year ended December 31, 2017 is due to the implementation of ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting . This ASU requires all income tax effects of awards to be recognized as income tax expense or benefit in the income statement when the awards vest or are settled. Implementation of the ASU was effective January 1, 2017 and resulted in approximately $935,000 of income tax benefit for the year ended December 31, 2017 . Years Ended December 31, 2017 2016 2015 Stock and ESPP Options Pre-tax compensation expense $ 121 $ 76 $ 101 Income tax expense (benefit) (322 ) 18 4 Stock and ESPP option expense, net of income taxes $ (201 ) $ 94 $ 105 Restricted Stock Awards Pre-tax compensation expense $ 2,706 $ 2,524 $ 2,169 Income tax benefit (1,561 ) (883 ) (749 ) Restricted stock awards expense, net of income taxes $ 1,145 $ 1,641 $ 1,420 Total Share-Based Compensation: Pre-tax compensation expense $ 2,827 $ 2,600 $ 2,270 Income tax benefit (1,883 ) (865 ) (745 ) Total share-based compensation expense, net of income taxes $ 944 $ 1,735 $ 1,525
Stock Option Activity Under Stock Option Plans	Stock option activity under the Corporation's stock option plans, as of December 31, 2017 , and changes during the year ended December 31, 2017 , were as follows: Number of Weighted-Average Price Weighted Average Aggregate Outstanding at January 1, 2017 260,211 $ 19.26 Exercised (104,748 ) $ 22.90 Canceled (2,811 ) $ 22.21 Outstanding December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499 Vested and Expected to Vest at December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499 Exercisable at December 31, 2017 152,652 $ 16.71 2.36 $ 3,870,499
Summary of Unvested RSAs Outstanding	The following table summarizes information on unvested RSAs outstanding as of December 31, 2017 : Number of Weighted-Average Unvested RSAs at January 1, 2017 328,347 $ 22.87 Granted 132,710 $ 40.47 Forfeited (4,702 ) $ 23.63 Vested (89,362 ) $ 20.53 Unvested RSAs at December 31, 2017 366,993 $ 29.79

Pension and Other Post Retire53

Pension and Other Post Retirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Schedule of Plans' Funded Status and Amounts Recognized in the Balance Sheets	The table below sets forth the plans’ funded status and amounts recognized in the consolidated balance sheets at December 31 , using measurement dates of December 31, 2017 and 2016 . 2017 2016 Change in Benefit Obligation: Benefit obligation at beginning of year $ 84,090 $ 71,747 Service cost 10 9 Interest cost 3,353 3,273 Actuarial loss 3,686 2,679 Benefits paid (5,179 ) (5,263 ) Plan settlements (3,803 ) Net transfers in from Ameriana acquisition 11,645 Benefit obligation at end of year $ 82,157 $ 84,090 Change in Plan Assets: Fair value of plan assets at beginning of year $ 83,557 $ 71,396 Actual return on plan assets 9,968 6,959 Employer contributions 670 739 Benefits paid (5,179 ) (5,263 ) Plan settlements (3,803 ) Ameriana acquisition 9,726 End of year 85,213 83,557 Funded status at end of year $ 3,056 $ (533 ) Assets and Liabilities Recognized in the Balance Sheets: Deferred tax asset $ 3,474 $ 7,041 Assets $ 7,660 $ 5,028 Liabilities $ 4,604 $ 5,561 Amounts Recognized in Accumulated Other Comprehensive Income Not Yet Recognized as Components of Net Periodic Cost, net of tax, consist of: Accumulated loss $ (10,360 ) $ (12,624 ) Prior service cost (393 ) (451 ) $ (10,753 ) $ (13,075 )
Schedule of Accumulated Benefit Obligation in Excess of Plan Assets	Information for pension plans with an accumulated benefit obligation in excess of plan assets is included in the table below. December 31, 2017 December 31, 2016 Projected benefit obligation $ 4,604 $ 5,561 Accumulated benefit obligation $ 4,604 $ 5,561 Fair value of plan assets $ — $ —
Schedule of Net Periodic Pension Costs	The following table shows the components of net periodic pension costs: December 31, 2017 December 31, 2016 December 31, 2015 Service cost $ 10 $ 9 $ 55 Interest cost 3,353 3,273 3,087 Expected return on plan assets (4,778 ) (4,508 ) (4,471 ) Amortization of prior service costs 90 79 64 Amortization of net loss 1,218 1,656 1,722 Settlement loss recognized 761 Net periodic pension cost $ 654 $ 509 $ 457
Schedule of Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss)	Other changes in plan assets and benefit obligations recognized in other comprehensive income: December 31, 2017 December 31, 2016 December 31, 2015 Net periodic pension cost $ 654 $ 509 $ 457 Net gain (loss) 1,504 (228 ) 1,299 Amortization of loss 1,979 1,656 1,722 Amortization of prior service cost 90 79 64 Total recognized in other comprehensive income 3,573 1,507 3,085 Total recognized in net periodic pension cost and other comprehensive income $ 2,919 $ 998 $ 2,628
Schedule of Amounts in Accumulated Other Comprehensive Income to be Recognized over Next Fiscal Year	The estimated net loss and transition obligation for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into net periodic pension cost over the next fiscal year are: December 31, 2017 December 31, 2016 December 31, 2015 Amortization of net loss $ (830 ) $ (1,208 ) $ (1,505 ) Amortization of prior service cost (87 ) (90 ) (61 ) Total $ (917 ) $ (1,298 ) $ (1,566 )
Schedule of Assumptions Used	Significant assumptions include: December 31, 2017 December 31, 2016 December 31, 2015 Weighted-average Assumptions Used to Determine Benefit Obligation: Discount rate 3.60 % 4.20 % 4.50 % Rate of compensation increase for accruing active participants n/a 3.00 % 3.00 % Weighted-average Assumptions Used to Determine Cost: Discount rate 4.20 % 4.50 % 4.00 % Expected return on plan assets 6.00 % 6.00 % 6.00 % Rate of compensation increase for accruing active participants n/a 3.00 % 3.00 %
Schedule of Expected Benefit Payments	The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid as of December 31, 2017 . The minimum contribution required in 2018 will likely be zero , but the Corporation may decide to make a discretionary contribution during the year. 2018 $ 5,586 2019 5,641 2020 5,609 2021 5,476 2022 5,377 After 2022 25,652 $ 53,341
Schedule of Allocation of Plan Assets	Plan assets are re-balanced quarterly. At December 31, 2017 and 2016 , plan assets by category are as follows: December 31, 2017 December 31, 2016 Actual Target Actual Target Cash and cash equivalents 6.0 % 3.0 % 4.5 % 3.0 % Equity securities 52.4 55.0 55.8 55.0 Debt securities 39.6 40.0 37.7 40.0 Alternative investments 2.0 2.0 2.0 2.0 100.0 % 100.0 % 100.0 % 100.0 % Following is a description of the valuation methodologies used for pension plan assets measured at fair value on a recurring basis, as well as the general classification of pension plan assets pursuant to the valuation hierarchy. Where quoted market prices are available in an active market, plan assets are classified within Level 1 of the valuation hierarchy. Level 1 plan assets total $78,280,000 and $64,064,000 as of December 31, 2017 and 2016 , respectively, and include cash and cash equivalents, common stocks, mutual funds and corporate bonds and notes. If quoted market prices are not available, then fair values are estimated by using pricing models, quoted prices of plan assets with similar characteristics or discounted cash flows. Level 2 plan assets total $6,933,000 and $19,493,000 as of December 31, 2017 and 2016 , respectively, and include governmental agencies, taxable municipal bonds, common collective trust investments (which are classified below as Party-in-Interest Investments - common bond fund and common equity fund) and certificates of deposit. In certain cases where Level 1 or Level 2 inputs are not available, plan assets are classified within Level 3 of the hierarchy. There are no assets classified within Level 3 of the hierarchy at December 31, 2017 and 2016 . Fair Value Measurements Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs December 31, 2017 Fair Value (Level 1) (Level 2) (Level 3) Cash & Cash Equivalents $ 5,123 $ 5,123 Corporate Bonds and Notes 14,598 14,598 Government Agency and Municipal Bonds and Notes 5,679 $ 5,679 Certificates of Deposit 1,254 1,254 Party-in-Interest Investments Common Stock 2,545 2,545 Mutual Funds Taxable Bond 12,198 12,198 Large Cap Equity 22,137 22,137 Mid Cap Equity 10,676 10,676 Small Cap Equity 5,264 5,264 International Equity 4,030 4,030 Specialty Alternative Equity 1,709 1,709 $ 85,213 $ 78,280 $ 6,933 Fair Value Measurements Using Quoted Prices in Significant Other Observable Inputs Significant December 31, 2016 Fair Value (Level 1) (Level 2) (Level 3) Cash & Cash Equivalents $ 3,778 $ 3,778 Corporate Bonds and Notes 10,646 10,646 Government Agency and Municipal Bonds and Notes 6,855 $ 6,855 Certificates of Deposit 1,268 1,268 Party-in-Interest Investments Common Stock 2,278 2,278 Common Bond Fund 4,744 4,744 Common Equity Fund 6,626 6,626 Mutual Funds Taxable Bond 7,974 7,974 Large Cap Equity 19,611 19,611 Mid Cap Equity 10,304 10,304 Small Cap Equity 4,680 4,680 International Equity 3,093 3,093 Specialty Alternative Equity 1,700 1,700 $ 83,557 $ 64,064 $ 19,493

Income Tax (Tables)

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Reconciliation of Federal Statutory to Actual Tax Expense	The reconciliation between income tax expense expected at the U.S. federal statutory tax rate and the reported income tax expense is summarized in the following table for years ended December 31, 2017 , 2016 , 2015 : 2017 2016 2015 Reconciliation of Federal Statutory to Actual Tax Expense: Federal Statutory Income Tax at 35% $ 46,758 $ 38,031 $ 31,867 Tax-exempt Interest Income (11,127 ) (8,749 ) (7,083 ) Basis Difference on Sale of Insurance Subsidiary 2,252 Stock Compensation (893 ) (61 ) (31 ) Earnings on Life Insurance (2,302 ) (1,486 ) (1,012 ) Tax Credits (811 ) (564 ) (583 ) Tax Cuts and Jobs Act - Rate Reform Impact 5,120 Other 779 438 255 Income Tax Expense $ 37,524 $ 27,609 $ 25,665
Components of Income Tax Expense (Benefit)	Income tax expense consists of the following components for the years ended December 31, 2017 , 2016 , 2015 : 2017 2016 2015 Income Tax Expense for the Year Ended December 31: Currently Payable: Federal $ 22,001 $ 18,998 $ 21,221 State Deferred: Federal 9,969 8,233 3,952 Tax Cuts and Jobs Act - Rate Reform Impact 5,120 State 434 378 492 Income Tax Expense $ 37,524 $ 27,609 $ 25,665
Deferred Tax Assets and Liabilities	Significant components of the net deferred tax assets (liabilities) resulting from temporary differences were as follows at December 31, 2017 and 2016 : 2017 2016 Deferred Tax Asset at December 31: Assets: Differences in Accounting for Loan Losses $ 19,526 $ 26,315 Differences in Accounting for Loan Fees 1,458 1,918 Differences in Accounting for Loans and Securities 3,681 5,689 Deferred Compensation 4,448 3,471 Difference in Accounting for Pensions and Other Employee Benefits 83 Federal & State Income Tax Loss Carryforward and Credits 10,829 16,643 Other 365 4,210 Total Assets 40,307 58,329 Liabilities: Differences in Depreciation Methods 5,245 8,216 Difference in Accounting for Pensions and Other Employee Benefits 823 State Income Tax 58 237 Net Unrealized Gain on Securities Available for Sale 2,898 557 Gain on FDIC Modified Whole Bank Transaction 602 1,126 Other 3,897 623 Total Liabilities 13,523 10,759 Net Deferred Tax Asset Before Valuation Allowance 26,784 47,570 Valuation allowance: Beginning Balance (9,815 ) (15,736 ) Decrease/(Increase) During the Year 2,849 5,921 Ending Balance (6,966 ) (9,815 ) Net Deferred Tax Asset $ 19,818 $ 37,755

Net Income Per Share (Tables)

Net Income Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Net Income Per Share	The following table reconciles basic and diluted net income per share for the years indicated: 2017 2016 2015 Weighted-Average Shares Weighted-Average Shares Weighted-Average Shares Basic net income per share: Net income available to common stockholders $ 96,070 45,181,221 $ 2.13 $ 81,051 40,767,343 $ 1.99 $ 65,384 37,816,399 $ 1.73 Effect of dilutive stock options and restricted stock awards 221,757 245,790 271,834 Diluted net income per share: Net income available to common stockholders $ 96,070 45,402,978 $ 2.12 $ 81,051 41,013,133 $ 1.98 $ 65,384 38,088,233 $ 1.72

Quarterly Results of Operatio56

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Results of Operations (Unaudited)	The following table sets forth certain quarterly results for the years ended December 31, 2017 and 2016 : 2017 2016 First Second Third Fourth First Second Third Fourth Interest income $ 68,234 $ 71,467 $ 84,847 $ 90,348 $ 61,227 $ 62,704 $ 64,376 $ 65,005 Interest expense 7,235 8,367 10,427 11,583 6,772 6,742 6,694 6,631 Net interest income 60,999 63,100 74,420 78,765 54,455 55,962 57,682 58,374 Provision for loan losses 2,385 2,875 2,083 1,800 550 790 1,900 2,417 Net interest income after provision for loan losses 58,614 60,225 72,337 76,965 53,905 55,172 55,782 55,957 Non-interest income 14,846 18,434 18,668 19,061 15,837 16,385 16,861 16,120 Non-interest expense 43,099 47,316 58,708 56,433 46,475 44,835 44,115 41,934 Income before income tax expense 30,361 31,343 32,297 39,593 23,267 26,722 28,528 30,143 Income tax expense 7,168 7,207 7,939 15,210 5,574 6,716 7,469 7,850 Net income available to common stockholders $ 23,193 $ 24,136 $ 24,358 $ 24,383 $ 17,693 $ 20,006 $ 21,059 $ 22,293 Basic EPS $ 0.57 $ 0.57 $ 0.50 $ 0.49 $ 0.43 $ 0.50 $ 0.51 $ 0.55 Diluted EPS $ 0.56 $ 0.57 $ 0.50 $ 0.49 $ 0.43 $ 0.49 $ 0.51 $ 0.55 Average Shares Outstanding: Basic 40,984,481 42,038,824 48,431,880 49,144,310 40,690,573 40,751,720 40,779,423 40,846,650 Diluted 41,220,586 42,243,539 48,643,774 49,379,303 40,916,972 40,969,111 41,025,784 41,124,179

Condensed Financial Informati57

Condensed Financial Information (parent company only) (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule of Parent Company Information, Condensed Balance Sheets	Condensed Balance Sheets December 31, 2017 December 31, 2016 Assets Cash $ 31,527 $ 31,944 Investment in subsidiaries 1,411,360 978,291 Investment securities 31 18,765 Premises and equipment 1,252 1,260 Interest receivable 5 47 Goodwill 448 448 Cash surrender value of life insurance 787 1,082 Tax asset, deferred and receivable 521 Other assets 3,480 5,274 Total assets $ 1,448,890 $ 1,037,632 Liabilities Subordinated debentures and term loans $ 138,241 $ 127,427 Interest payable 968 880 Other liabilities 6,218 7,668 Total liabilities 145,427 135,975 Stockholders' equity 1,303,463 901,657 Total liabilities and stockholders' equity $ 1,448,890 $ 1,037,632
Schedule of Parent Company Information, Condensed Statements of Income and Comprehensive Income	Condensed Statements of Income and Comprehensive Income December 31, 2017 December 31, 2016 December 31, 2015 Income Dividends from subsidiaries $ 33,014 $ 33,546 $ 39,032 Gain on the sale of insurance subsidiary 8,265 Gain on cancellation of subordinated debentures 1,250 Loss on sale of available for sale securities (50 ) Other income 350 143 197 Total income 33,314 33,689 48,744 Expenses Interest expense 7,572 7,185 6,661 Salaries and employee benefits 4,118 639 3,023 Net occupancy and equipment expenses 797 832 464 Other outside services 1,810 967 1,455 Professional services 442 279 636 Other expenses (385 ) (470 ) 1,234 Total expenses 14,354 9,432 13,473 Income before income tax benefit (expense) and equity in undistributed income of subsidiaries 18,960 24,257 35,271 Income tax benefit (expense) 5,946 3,243 (974 ) Income before equity in undistributed income of subsidiaries 24,906 27,500 34,297 Equity in undistributed income of subsidiaries 71,164 53,551 31,087 Net income available to common stockholders $ 96,070 $ 81,051 $ 65,384 Net income $ 96,070 $ 81,051 $ 65,384 Other comprehensive income (loss) 10,673 (12,219 ) 268 Comprehensive income $ 106,743 $ 68,832 $ 65,652
Schedule of Parent Company Information, Condensed Statement of Cash Flows	Condensed Statement of Cash Flows Year Ended December 31, 2017 2016 2015 Cash Flow From Operating Activities: Net income $ 96,070 $ 81,051 $ 65,384 Adjustments to Reconcile Net Income to Net Cash: Share-based compensation 1,215 1,166 843 Distributions in excess of (equity in undistributed) income of subsidiaries (71,164 ) (53,551 ) (31,087 ) Gain on sale of insurance subsidiary (8,265 ) Gain on cancellation of subordinated debentures (1,250 ) Loss on sale of available for sale securities 50 Net Change in: Other assets 3,358 833 (441 ) Other liabilities (1,900 ) 849 (1,486 ) Investment in subsidiaries - operating activities 1,112 (1,938 ) 197 Net cash provided by operating activities 28,741 28,410 23,895 Cash Flow From Investing Activities: Purchase of securities available for sale (19,804 ) Net cash received (paid) in acquisition 37 (14,500 ) Proceeds from business divestitures 16,000 Other 575 Net cash provided (used) in investing activities 37 (19,804 ) 2,075 Cash Flow From Financing Activities: Cash dividends (31,820 ) (22,203 ) (15,654 ) Repayment of borrowings (3,750 ) Stock issued under employee benefit plans 519 462 460 Stock issued under dividend reinvestment and stock purchase plan 991 835 661 Stock options exercised 2,398 2,602 1,531 Stock redeemed (1,283 ) (1,980 ) (1,640 ) Net cash used by financing activities (29,195 ) (20,284 ) (18,392 ) Cash, beginning of the year 31,944 43,622 36,044 Cash, end of year $ 31,527 $ 31,944 $ 43,622

Nature of Operations and Summ58

Nature of Operations and Summary of Significant Accounting Policies - Allowance for Loan Losses (Details)	12 Months Ended
	Dec. 31, 2017USD ($)key_element
Accounting Policies [Abstract]
Number of key element used in assessing the appropriateness of the allowance for loan losses | key_element	3
Commercial relationships threshold that exhibit credit weaknesses | $	$ 500,000

Nature of Operations and Summ59

Nature of Operations and Summary of Significant Accounting Policies - Premises and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Premises and Equipment [Line Items]
Estimated useful lives of assets	3 years
Maximum
Premises and Equipment [Line Items]
Estimated useful lives of assets	40 years

Nature of Operations and Summ60

Nature of Operations and Summary of Significant Accounting Policies - Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Intangible Assets [Abstract]
Estimated useful lives of intangible assets	2 years
Maximum
Intangible Assets [Abstract]
Estimated useful lives of intangible assets	20 years

Nature of Operations and Summ61

Nature of Operations and Summary of Significant Accounting Policies - Requisite Service Period, Stock Award Plans (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Schedule of Stock Options and Restricted Stock Award Plans [Line Items]
Requisite service period	2 years
Maximum
Schedule of Stock Options and Restricted Stock Award Plans [Line Items]
Requisite service period	3 years

Acquisitions - Acquisitions Nar

Acquisitions - Acquisitions Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 14, 2017USD ($)bank_branchshares	May 19, 2017USD ($)bank_branchshares	Nov. 21, 2016USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)shares
Business Acquisition [Line Items]
Issuance of common stock related to acquisition					$ 321,431		$ 70,402
Common Stock
Business Acquisition [Line Items]
Stock issued as a part of acquisition (in shares) | shares					8,044,446		2,769,568
Issuance of common stock related to acquisition					$ 1,006		$ 346
IAB
Business Acquisition [Line Items]
Shares purchased (in shares) | shares			495,112
Percentage of interest acquired			12.10%
Value of acquired shares			$ 19,800
Purchase price per share (in dollars per share) | $ / shares			$ 40
Number of banking centers acquired | bank_branch	16
Stock issued as a part of acquisition (in shares) | shares	6,000,000
Issuance of common stock related to acquisition	$ 238,800
Total purchase price	258,600
Fair value of equity interest after adjustement				$ 19,800
Remeasurement loss				$ 50
Other intangible assets	17,403
Operating revenue					21,400
IAB | Core deposits
Business Acquisition [Line Items]
Other intangible assets	$ 13,638
Acquired intangible asset, expected useful life	10 years
IAB | Noncompete agreements
Business Acquisition [Line Items]
Other intangible assets	$ 3,765
Acquired intangible asset, expected useful life	2 years
IAB | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock	1.653
Arlington Bank
Business Acquisition [Line Items]
Percentage of interest acquired		100.00%
Number of banking centers acquired | bank_branch		3
Stock issued as a part of acquisition (in shares) | shares		2,100,000
Issuance of common stock related to acquisition		$ 82,600
Other intangible assets		4,526
Operating revenue					9,000
Arlington Bank | Core deposits
Business Acquisition [Line Items]
Other intangible assets		$ 4,526
Acquired intangible asset, expected useful life		10 years
Arlington Bank | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock		2.7245
Arlington Bank and IAB | Expenses directly attributable to acquisitions
Business Acquisition [Line Items]
Non-recurring expenses					$ 15,400

Acquisitions - Assets Acquired

Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 14, 2017	May 19, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 445,355			$ 244,000	$ 243,129
IAB
Business Acquisition [Line Items]
Cash and cash equivalents		$ 6,016
Interest-bearing time deposits		248,212
Investment securities		4,078
Loans held for sale		594
Loans		725,382
Premises and equipment		10,107
Federal Home Loan Bank stock		4,810
Interest receivable		3,445
Cash surrender value of life insurance		26,964
Other assets		11,780
Deposits		(862,271)
Securities sold under repurchase agreements		(17,915)
Federal Home Loan Bank Advances		(47,575)
Subordinated debentures		(10,583)
Interest payable		(1,005)
Other liabilities		(14,472)
Net tangible assets acquired		87,567
Core deposit intangible		17,403
Goodwill		153,636
Purchase price		$ 258,606
Arlington Bank
Business Acquisition [Line Items]
Cash and cash equivalents			$ 48,532
Interest-bearing time deposits			292
Loans held for sale			7,626
Loans			224,680
Premises and equipment			1,986
Federal Home Loan Bank stock			1,091
Interest receivable			653
Other assets			1,620
Deposits			(252,783)
Interest payable			(244)
Other liabilities			(3,106)
Net tangible assets acquired			30,347
Core deposit intangible			4,526
Goodwill			47,719
Purchase price			$ 82,592

Acquisitions - Schedule of Acqu

Acquisitions - Schedule of Acquired Loan Data (Details) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 14, 2017	May 19, 2017
Business Acquisition [Line Items]
Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30	$ 7,463
Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30	20,314
IAB
Business Acquisition [Line Items]
Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30	4,838	$ 4,838
Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30	14,131	14,131
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, subject to ASC 310-30		8,352
Fair Value of Acquired Loans at Acquisition Date, not subject to ASC 310-30		720,544
Gross Contractual Amounts Receivable at Acquisition Date, not subject to ASC 310-30		864,613
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, not subject to ASC 310-30		$ 9,786
Arlington Bank
Business Acquisition [Line Items]
Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30	2,625		$ 2,625
Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30	$ 6,183		6,183
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, subject to ASC 310-30			2,891
Fair Value of Acquired Loans at Acquisition Date, not subject to ASC 310-30			222,055
Gross Contractual Amounts Receivable at Acquisition Date, not subject to ASC 310-30			308,857
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, not subject to ASC 310-30			$ 2,741

Acquisitions - Pro Forma Inform

Acquisitions - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Total revenue (net interest income plus other income)	$ 380,324	$ 353,732
Net income	95,009	95,288
Net income available to common shareholders
Earnings per share:
Basic (in dollars per share)	$ 1.94	$ 1.95
Diluted (in dollars per share)	$ 1.93	$ 1.94

Restriction on Cash and Due F66

Restriction on Cash and Due From Banks (Details) $ in Thousands	Dec. 31, 2017USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Cash balance, Federal Home Loan Bank And Federal Reserve Bank	$ 5,826
Cash reserve with Federal Reserve Bank	14,522
Interest-bearing Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Cash amount that exceeded federally insured limits	$ 128,127

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Approximate Fair Values of Securities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Total available for sale
Amortized Cost	$ 986,565,000	$ 696,189,000
Gross Unrealized Gains	17,896,000	10,347,000
Gross Unrealized Losses	4,514,000	9,674,000
Investment securities available for sale	999,947,000	696,862,000
Total held to maturity
Amortized Cost	560,655,000	607,643,000
Gross Unrealized Gains	9,636,000	8,092,000
Gross Unrealized Losses	2,083,000	3,802,000
Fair Value	568,208,000	611,933,000
Total Investment Securities
Amortized Cost	1,547,220,000	1,303,832,000
Gross Unrealized Gains	27,532,000	18,439,000
Gross Unrealized Losses	6,597,000	13,476,000
Fair Value	1,568,155,000	1,308,795,000
State and municipal
Total available for sale
Amortized Cost	510,852,000	360,779,000
Gross Unrealized Gains	16,932,000	8,443,000
Gross Unrealized Losses	1,091,000	5,564,000
Investment securities available for sale	526,693,000	363,658,000
Total held to maturity
Amortized Cost	235,594,000	224,811,000
Gross Unrealized Gains	6,295,000	3,136,000
Gross Unrealized Losses	244,000	1,796,000
Fair Value	241,645,000	226,151,000
U.S. Government-sponsored mortgage-backed securities
Total available for sale
Amortized Cost	473,325,000	313,459,000
Gross Unrealized Gains	964,000	1,904,000
Gross Unrealized Losses	3,423,000	3,071,000
Investment securities available for sale	470,866,000	312,292,000
Total held to maturity
Amortized Cost	301,443,000	360,213,000
Gross Unrealized Gains	3,341,000	4,956,000
Gross Unrealized Losses	1,404,000	1,527,000
Fair Value	303,380,000	363,642,000
Corporate obligations
Total available for sale
Amortized Cost	31,000	31,000
Gross Unrealized Gains
Gross Unrealized Losses
Investment securities available for sale	31,000	31,000
Equity securities
Total available for sale
Amortized Cost	2,357,000	21,820,000
Gross Unrealized Gains
Gross Unrealized Losses		1,039,000
Investment securities available for sale	2,357,000	20,781,000
U.S. Government-sponsored agency securities
Total available for sale
Amortized Cost		100,000
Gross Unrealized Gains
Gross Unrealized Losses	0
Investment securities available for sale		100,000
Total held to maturity
Amortized Cost	22,618,000	22,619,000
Gross Unrealized Losses	435,000	479,000
Fair Value	22,183,000	$ 22,140,000
Foreign Investment
Total held to maturity
Amortized Cost	1,000,000
Fair Value	$ 1,000,000

Investment Securities - Narrati

Investment Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value of investments	$ 446,047,000	$ 510,297,000
Unrealized losses on mortgage-backed securities portfolio	4,514,000	9,674,000
Unrealized losses in available for sale and held to maturity portfolios	2,083,000	3,802,000
Carrying value of securities pledged as collateral	475,999,000	572,896,000	$ 637,358,000
Securities sold under repurchase agreements	136,639,000	145,936,000
Gross gains on securities sold	2,681,000	3,389,000	2,770,000
Gross losses from sale of available for sale securities	50,000	0	$ 100,000
Investments in Debt and Equity Securities, Reported at Less than Historical Cost
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Historical cost	452,644,000	523,773,000
Fair value of investments	$ 446,047,000	$ 510,297,000
Percent of the Corporation's available for sale and held to maturity portfolio	28.60%	39.10%
U.S. Government-Sponsored Mortgage-backed Securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 3,423,000	$ 3,071,000
Available-for-sale, number of securities in unrealized loss positions | security	63
Unrealized losses in available for sale and held to maturity portfolios	$ 1,404,000	1,527,000
Held-to-maturity, number of securities in unrealized loss positions | security	36
State and Municipal Securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 1,091,000	5,564,000
Available-for-sale, number of securities in unrealized loss positions | security	42
Unrealized losses in available for sale and held to maturity portfolios	$ 244,000	1,796,000
Held-to-maturity, number of securities in unrealized loss positions | security	28
U.S. Government-sponsored agency securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio	$ 0
Unrealized losses in available for sale and held to maturity portfolios	$ 435,000	479,000
Held-to-maturity, number of securities in unrealized loss positions | security	5
Equity securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Unrealized losses on mortgage-backed securities portfolio		$ 1,039,000

Investment Securities - Investm

Investment Securities - Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	$ 196,051	$ 330,902
Less than 12 Months, Gross Unrealized Losses	1,718	9,674
12 Months or Longer, Fair Value	103,991
12 Months or Longer, Gross Unrealized Losses	2,796
Total, Fair Value	300,042	330,902
Total, Gross Unrealized Losses	4,514	9,674
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	74,926	179,395
Less than 12 Months, Gross Unrealized Losses	652	3,802
12 Months or Longer, Fair Value	71,079
12 Months or Longer, Gross Unrealized Losses	1,431
Total, Fair Value	146,005	179,395
Total, Gross Unrealized Losses	2,083	3,802
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Less than 12 Months, Fair Value	270,977	510,297
Less than 12 Months, Gross Unrealized Losses	2,370	13,476
12 Months or Longer, Fair Value	175,070
12 Months or Longer, Gross Unrealized Losses	4,227
Total, Fair Value	446,047	510,297
Total, Gross Unrealized Losses	6,597	13,476
State and municipal
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	13,296	126,593
Less than 12 Months, Gross Unrealized Losses	198	5,564
12 Months or Longer, Fair Value	35,324
12 Months or Longer, Gross Unrealized Losses	893
Total, Fair Value	48,620	126,593
Total, Gross Unrealized Losses	1,091	5,564
U.S. Government-sponsored mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	182,755	185,544
Less than 12 Months, Gross Unrealized Losses	1,520	3,071
12 Months or Longer, Fair Value	68,667
12 Months or Longer, Gross Unrealized Losses	1,903
Total, Fair Value	251,422	185,544
Total, Gross Unrealized Losses	3,423	3,071
Equity securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value		18,765
Less than 12 Months, Gross Unrealized Losses		1,039
Total, Fair Value		18,765
Total, Gross Unrealized Losses		1,039
Government Agency and Municipal Bonds and Notes
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	9,988	19,121
Less than 12 Months, Gross Unrealized Losses	131	479
12 Months or Longer, Fair Value	12,196
12 Months or Longer, Gross Unrealized Losses	304
Total, Fair Value	22,184	19,121
Total, Gross Unrealized Losses	435	479
State and municipal
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	2,430	50,897
Less than 12 Months, Gross Unrealized Losses	36	1,796
12 Months or Longer, Fair Value	15,805
12 Months or Longer, Gross Unrealized Losses	208
Total, Fair Value	18,235	50,897
Total, Gross Unrealized Losses	244	1,796
U.S. Government-sponsored mortgage-backed securities
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	62,508	109,377
Less than 12 Months, Gross Unrealized Losses	485	1,527
12 Months or Longer, Fair Value	43,078
12 Months or Longer, Gross Unrealized Losses	919
Total, Fair Value	105,586	109,377
Total, Gross Unrealized Losses	$ 1,404	$ 1,527

Investment Securities - Amort70

Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available for Sale, Amortized Cost
Due in one year or less	$ 425
Due after one through five years	5,040
Due after five through ten years	74,921
Due after ten years	430,497
Amortized Cost	510,883
Total Investment Securities	986,565
Available for Sale, Fair Value
Due in one year or less	425
Due after one through five years	5,204
Due after five through ten years	78,806
Due after ten years	442,289
Fair Value	526,724
Total Investment Securities	999,947
Held to Maturity, Amortized Cost
Due in one year or less	12,015
Due after one through five years	76,146
Due after five through ten years	54,441
Due after ten years	116,610
Amortized Cost	259,212
Amortized Cost	560,655	$ 607,643
Held to Maturity, Fair Value
Due in one year or less	12,158
Due after one through five years	76,334
Due after five through ten years	55,679
Due after ten years	120,657
Fair Value	264,828
Total Investment Securities	568,208	611,933
U.S. Government-sponsored mortgage-backed securities
Available for Sale, Amortized Cost
Without single maturity date	473,325
Available for Sale, Fair Value
Without single maturity date	470,866
Held to Maturity, Amortized Cost
Without single maturity date	301,443
Amortized Cost	301,443	360,213
Held to Maturity, Fair Value
Without single maturity date	303,380
Total Investment Securities	303,380	$ 363,642
Equity securities
Available for Sale, Amortized Cost
Without single maturity date	2,357
Available for Sale, Fair Value
Without single maturity date	$ 2,357

Loans and Allowance - Narrative

Loans and Allowance - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Loans held for sale	$ 7,216				$ 2,929				$ 7,216	$ 2,929
Allowance for loan losses	75,032				66,037				75,032	66,037	$ 62,453	$ 63,964
Increase in allowance for loan losses									8,995
Net charge offs									148
Increase in net charge offs									1,925
Provision for loan losses	1,800	$ 2,083	$ 2,875	$ 2,385	2,417	$ 1,900	$ 790	$ 550	9,143	5,657	417
Increase in provision for loan losses									$ 3,486
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of troubled debt restructured loans									40.00%
Residential
Receivables [Abstract]
Allowance for loan losses	13,537				11,755				$ 13,537	11,755	11,139	$ 13,152
Provision for loan losses									2,391	1,515	$ 310
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans for which formal foreclosure proceedings are in process	$ 2,302				$ 1,530				$ 2,302	$ 1,530

Loans and Allowance - Compositi

Loans and Allowance - Composition of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 6,751,199	$ 5,139,645
Allowance for loan losses	(75,032)	(66,037)	$ (62,453)	$ (63,964)
Net Loans	6,676,167	5,073,608
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,493,493	1,194,646
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	121,757	79,689
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	612,219	418,703
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,562,691	1,953,062
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	962,765	739,169
Allowance for loan losses	(13,537)	(11,755)	(11,139)	(13,152)
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	514,021	418,525
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	86,935	77,479
Allowance for loan losses	(3,732)	(2,923)	(2,689)	(2,658)
Lease financing receivables, net of unearned income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,527	311
Allowance for loan losses	(2)	(2)	$ (2)	$ (3)
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 394,791	$ 258,061

Loans and Allowance - Changes i

Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan losses:
Beginning balance				$ 66,037				$ 62,453	$ 66,037	$ 62,453	$ 63,964
Provision for losses	$ 1,800	$ 2,083	$ 2,875	2,385	$ 2,417	$ 1,900	$ 790	550	9,143	5,657	417
Recoveries on loans									4,880	5,356	6,344
Loans charged off									(5,028)	(7,429)	(8,272)
Ending balance	75,032				66,037				75,032	66,037	62,453
Commercial
Allowance for loan losses:
Beginning balance				27,696				26,478	27,696	26,478	28,824
Provision for losses									2,515	1,876	(1,901)
Recoveries on loans									1,590	1,806	1,911
Loans charged off									(1,383)	(2,464)	(2,356)
Ending balance	30,418				27,696				30,418	27,696	26,478
Commercial Real Estate
Allowance for loan losses:
Beginning balance				23,661				22,145	23,661	22,145	19,327
Provision for losses									3,159	1,834	1,710
Recoveries on loans									2,260	2,090	2,545
Loans charged off									(1,737)	(2,408)	(1,437)
Ending balance	27,343				23,661				27,343	23,661	22,145
Consumer
Allowance for loan losses:
Beginning balance				2,923				2,689	2,923	2,689	2,658
Provision for losses									1,078	432	299
Recoveries on loans									324	369	352
Loans charged off									(593)	(567)	(620)
Ending balance	3,732				2,923				3,732	2,923	2,689
Residential
Allowance for loan losses:
Beginning balance				11,755				11,139	11,755	11,139	13,152
Provision for losses									2,391	1,515	310
Recoveries on loans									706	1,091	1,536
Loans charged off									(1,315)	(1,990)	(3,859)
Ending balance	13,537				11,755				13,537	11,755	11,139
Finance Leases
Allowance for loan losses:
Beginning balance				$ 2				$ 2	2	2	3
Provision for losses											(1)
Recoveries on loans
Loans charged off
Ending balance	$ 2				$ 2				$ 2	$ 2	$ 2

Loans and Allowance - Allowance

Loans and Allowance - Allowance for Credit Losses and Loan Portfolio by Loan Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	$ 1,637	$ 888
Allowance balances - Collectively evaluated for impairment	73,395	65,149
Total Allowance for Loan Losses	75,032	66,037	$ 62,453	$ 63,964
Loan balances - Individually evaluated for impairment	29,731	30,579
Loan balances - Collectively evaluated for impairment	6,696,199	5,065,844
Loans	6,751,199	5,139,645
Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality	25,269	43,222
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	666	37
Allowance balances - Collectively evaluated for impairment	29,752	27,659
Total Allowance for Loan Losses	30,418	27,696	26,478	28,824
Loan balances - Individually evaluated for impairment	4,776	4,762
Loan balances - Collectively evaluated for impairment	2,003,844	1,520,981
Loans	2,010,041	1,532,396
Commercial | Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality	1,421	6,653
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	567	553
Allowance balances - Collectively evaluated for impairment	26,776	23,108
Total Allowance for Loan Losses	27,343	23,661	22,145	19,327
Loan balances - Individually evaluated for impairment	21,009	21,358
Loan balances - Collectively evaluated for impairment	3,131,589	2,315,686
Loans	3,174,910	2,371,765
Commercial Real Estate | Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality	22,312	34,721
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	3,732	2,923
Total Allowance for Loan Losses	3,732	2,923	2,689	2,658
Loan balances - Individually evaluated for impairment	5	9
Loan balances - Collectively evaluated for impairment	86,930	77,470
Loans	86,935	77,479
Consumer | Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality
Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	404	298
Allowance balances - Collectively evaluated for impairment	13,133	11,457
Total Allowance for Loan Losses	13,537	11,755	11,139	13,152
Loan balances - Individually evaluated for impairment	3,941	4,450
Loan balances - Collectively evaluated for impairment	1,471,309	1,151,396
Loans	1,476,786	1,157,694
Residential | Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality	1,536	1,848
Finance Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	2	2
Total Allowance for Loan Losses	2	2	$ 2	$ 3
Loan balances - Individually evaluated for impairment
Loan balances - Collectively evaluated for impairment	2,527	311
Loans	2,527	311
Finance Leases | Loans acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan balances - Loans Acquired with Deteriorated Credit Quality

Loans and Allowance - Summary o

Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 28,724	$ 29,998
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	3,275	1,839
Agriculture production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,027	1,329
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	65	73
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	12,951	15,754
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	9,444	9,523
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,928	1,457
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 34	$ 23

Loans and Allowance - Composi76

Loans and Allowance - Composition of Impaired Loans by Loan Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unpaid Principal Balance
Impaired loans with no related allowance	$ 75,547	$ 100,416	$ 134,581
Impaired loans with related allowance	4,158	4,963	7,953
Total Impaired Loans	79,705	105,379	142,534
Recorded Investment
Impaired loans with no related allowance	49,308	68,371	90,975
Impaired loans with related allowance	3,379	3,679	6,552
Total Impaired Loans	52,687	72,050	97,527
Related Allowance	1,233	612	1,842
Average Recorded Investment
Impaired loans with no related allowance	57,428	74,592	96,423
Impaired loans with related allowance	4,227	3,718	6,945
Total Impaired Loans	61,655	78,310	103,368
Interest Income Recognized
Impaired loans with no related allowance	2,126	3,905	4,217
Impaired loans with related allowance	4		38
Total Impaired Loans	2,130	3,905	4,255
Commercial and industrial loans
Unpaid Principal Balance
Impaired loans with no related allowance	14,110	17,645	22,151
Impaired loans with related allowance	812		3,043
Recorded Investment
Impaired loans with no related allowance	3,850	10,074	11,669
Impaired loans with related allowance	782		2,690
Related Allowance	552		1,247
Average Recorded Investment
Impaired loans with no related allowance	7,653	13,393	12,578
Impaired loans with related allowance	1,517		2,752
Interest Income Recognized
Impaired loans with no related allowance	186	499	488
Impaired loans with related allowance			38
Agriculture production financing and other loans to farmers
Unpaid Principal Balance
Impaired loans with no related allowance	1,595	757	370
Impaired loans with related allowance	357	660	466
Recorded Investment
Impaired loans with no related allowance	1,238	680	361
Impaired loans with related allowance	327	660	466
Related Allowance	114	36	30
Average Recorded Investment
Impaired loans with no related allowance	1,304	750	439
Impaired loans with related allowance	327	691	538
Interest Income Recognized
Impaired loans with no related allowance	20	3
Impaired loans with related allowance
Construction
Unpaid Principal Balance
Impaired loans with no related allowance	2,530	5,946	4,551
Recorded Investment
Impaired loans with no related allowance	1,396	3,178	2,336
Average Recorded Investment
Impaired loans with no related allowance	1,420	3,255	3,662
Interest Income Recognized
Impaired loans with no related allowance	64	258	157
Commercial and farmland
Unpaid Principal Balance
Impaired loans with no related allowance	51,829	67,936	95,930
Impaired loans with related allowance	2,989	4,238	2,144
Recorded Investment
Impaired loans with no related allowance	39,651	49,731	69,024
Impaired loans with related allowance	2,270	2,985	1,933
Related Allowance	567	553	392
Average Recorded Investment
Impaired loans with no related allowance	43,445	51,740	71,569
Impaired loans with related allowance	2,383	2,989	1,868
Interest Income Recognized
Impaired loans with no related allowance	1,734	2,978	3,328
Impaired loans with related allowance	4
Residential
Unpaid Principal Balance
Impaired loans with no related allowance	5,403	8,039	11,262
Impaired loans with related allowance		65	2,300
Recorded Investment
Impaired loans with no related allowance	3,133	4,664	7,338
Impaired loans with related allowance		34	1,463
Related Allowance		23	173
Average Recorded Investment
Impaired loans with no related allowance	3,558	5,410	7,926
Impaired loans with related allowance		38	1,787
Interest Income Recognized
Impaired loans with no related allowance	122	167	244
Impaired loans with related allowance
Home equity
Unpaid Principal Balance
Impaired loans with no related allowance	80	82	297
Recorded Investment
Impaired loans with no related allowance	40	44	247
Average Recorded Investment
Impaired loans with no related allowance	48	44	249
Interest Income Recognized
Impaired loans with no related allowance
Other commercial loans
Unpaid Principal Balance
Impaired loans with no related allowance		11	20
Recorded Investment
Impaired loans with no related allowance
Average Recorded Investment
Impaired loans with no related allowance
Interest Income Recognized
Impaired loans with no related allowance

Loans and Allowance - Credit Qu

Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 6,751,199	$ 5,139,645
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,493,493	1,194,646
Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	121,757	79,689
Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	612,219	418,703
Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	2,562,691	1,953,062
Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	962,765	739,169
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	514,021	418,525
Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	86,935	77,479
Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans	2,527	311
Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	394,791	258,061
Commercial Pass
Financing Receivable, Recorded Investment [Line Items]
Loans	5,099,464	3,769,920
Commercial Pass | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	1,418,401	1,117,545
Commercial Pass | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	73,800	30,712
Commercial Pass | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	587,906	398,646
Commercial Pass | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	2,408,329	1,811,367
Commercial Pass | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	185,725	146,251
Commercial Pass | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	28,554	7,310
Commercial Pass | Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans	2,527	228
Commercial Pass | Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	394,222	257,861
Commercial Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans	154,573	124,863
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	51,336	30,919
Commercial Special Mention | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	27,502	25,273
Commercial Special Mention | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	828	3,490
Commercial Special Mention | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	70,074	60,028
Commercial Special Mention | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	4,376	5,106
Commercial Special Mention | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	457	47
Commercial Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans	129,218	159,215
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	23,386	46,182
Commercial Substandard | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	20,018	23,704
Commercial Substandard | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	981	1,858
Commercial Substandard | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	79,769	80,626
Commercial Substandard | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	4,209	6,046
Commercial Substandard | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	286	516
Commercial Substandard | Finance Leases
Financing Receivable, Recorded Investment [Line Items]
Loans		83
Commercial Substandard | Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	569	200
Commercial Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans	2,407
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Loans	370
Commercial Doubtful | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	387
Commercial Doubtful | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	1,536
Commercial Doubtful | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	114
Commercial Loss
Financing Receivable, Recorded Investment [Line Items]
Loans	50
Commercial Loss | Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment [Line Items]
Loans	50
Consumer Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	1,354,790	1,076,417
Consumer Performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	22,374	14,636
Consumer Performing | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	2,980	1,034
Consumer Performing | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	759,900	574,054
Consumer Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	482,661	409,237
Consumer Performing | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	86,875	77,456
Consumer Non Performing
Financing Receivable, Recorded Investment [Line Items]
Loans	10,697	9,230
Consumer Non Performing | Construction
Financing Receivable, Recorded Investment [Line Items]
Loans	130	73
Consumer Non Performing | Commercial and farmland
Financing Receivable, Recorded Investment [Line Items]
Loans	3	7
Consumer Non Performing | Residential
Financing Receivable, Recorded Investment [Line Items]
Loans	8,441	7,712
Consumer Non Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans	2,063	1,415
Consumer Non Performing | Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 60	$ 23

Loans and Allowance - Past Due

Loans and Allowance - Past Due Aging of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 6,703,256	$ 5,095,918
Loans 90 Days And Accruing	924	112
Non-Accrual	28,724	29,998
Total Past Due & Non-Accrual	47,943	43,727
Total	6,751,199	5,139,645
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	16,773	9,490
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,522	4,127
Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,487,221	1,192,079
Loans 90 Days And Accruing		100
Non-Accrual	3,275	1,839
Total Past Due & Non-Accrual	6,272	2,567
Total	1,493,493	1,194,646
Commercial and industrial loans | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,967	466
Commercial and industrial loans | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	30	162
Agricultural production financing and other loans to farmers
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	120,720	78,360
Loans 90 Days And Accruing
Non-Accrual	1,027	1,329
Total Past Due & Non-Accrual	1,037	1,329
Total	121,757	79,689
Agricultural production financing and other loans to farmers | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10
Agricultural production financing and other loans to farmers | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	610,896	415,975
Loans 90 Days And Accruing	65
Non-Accrual	65	73
Total Past Due & Non-Accrual	1,323	2,728
Total	612,219	418,703
Construction | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,193	2,655
Construction | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due
Commercial and farmland
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,542,048	1,932,896
Loans 90 Days And Accruing	603
Non-Accrual	12,951	15,754
Total Past Due & Non-Accrual	20,643	20,166
Total	2,562,691	1,953,062
Commercial and farmland | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	6,923	1,385
Commercial and farmland | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	166	3,027
Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	948,947	725,338
Loans 90 Days And Accruing	56	9
Non-Accrual	9,444	9,523
Total Past Due & Non-Accrual	13,818	13,831
Total	962,765	739,169
Residential | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,010	3,664
Residential | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	308	635
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	510,362	415,969
Loans 90 Days And Accruing	175	3
Non-Accrual	1,928	1,457
Total Past Due & Non-Accrual	3,659	2,556
Total	514,021	418,525
Home equity | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,372	850
Home equity | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	184	246
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	85,744	76,929
Loans 90 Days And Accruing	25
Non-Accrual	34	23
Total Past Due & Non-Accrual	1,191	550
Total	86,935	77,479
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	298	470
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	834	57
Lease financing receivables, net of unearned income
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,527	311
Non-Accrual
Total Past Due & Non-Accrual
Total	2,527	311
Other commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	394,791	258,061
Non-Accrual
Total Past Due & Non-Accrual
Total	394,791	258,061
Other commercial loans | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due

Loans and Allowance - Summary79

Loans and Allowance - Summary of Troubled Debt Restructurings (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 3,004	$ 7,165
Post-Modification Recorded Balance	$ 2,902	$ 7,035
Number of Loans | loan	34	37
Commercial and industrial loans
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 599	$ 410
Post-Modification Recorded Balance	$ 376	$ 410
Number of Loans | loan	3	4
Agriculture production financing and other loans to farmers
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 387	$ 1,368
Post-Modification Recorded Balance	$ 387	$ 1,234
Number of Loans | loan	3	4
Commercial and farmland
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 1,022	$ 3,978
Post-Modification Recorded Balance	$ 1,156	$ 3,954
Number of Loans | loan	8	7
Residential
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 788	$ 1,126
Post-Modification Recorded Balance	$ 862	$ 1,183
Number of Loans | loan	15	17
Home equity
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 195	$ 266
Post-Modification Recorded Balance	$ 107	$ 244
Number of Loans | loan	4	4
Individuals' loans for household and other personal expenditures
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Balance	$ 13	$ 17
Post-Modification Recorded Balance	$ 14	$ 10
Number of Loans | loan	1	1

Loans and Allowance - Summary80

Loans and Allowance - Summary of Troubled Debt Restructurings by Modification (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Total Modification	$ 2,717	$ 6,263
Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification	1,295	1,195
Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification	939	1,215
Combination
Financing Receivable, Modifications [Line Items]
Total Modification	483	3,853
Commercial and industrial loans
Financing Receivable, Modifications [Line Items]
Total Modification	369	397
Commercial and industrial loans | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification	203
Commercial and industrial loans | Combination
Financing Receivable, Modifications [Line Items]
Total Modification	166	397
Agriculture production financing and other loans to farmers
Financing Receivable, Modifications [Line Items]
Total Modification	387	672
Agriculture production financing and other loans to farmers | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification	387	660
Agriculture production financing and other loans to farmers | Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification		12
Commercial and farmland
Financing Receivable, Modifications [Line Items]
Total Modification	996	3,753
Commercial and farmland | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification	705	297
Commercial and farmland | Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification	59
Commercial and farmland | Combination
Financing Receivable, Modifications [Line Items]
Total Modification	232	3,456
Residential
Financing Receivable, Modifications [Line Items]
Total Modification	846	1,166
Residential | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification		238
Residential | Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification	761	928
Residential | Combination
Financing Receivable, Modifications [Line Items]
Total Modification	85
Home equity
Financing Receivable, Modifications [Line Items]
Total Modification	105	266
Home equity | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification
Home equity | Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification	105	266
Home equity | Combination
Financing Receivable, Modifications [Line Items]
Total Modification
Individuals' loans for household and other personal expenditures
Financing Receivable, Modifications [Line Items]
Total Modification	14	9
Individuals' loans for household and other personal expenditures | Term Modification
Financing Receivable, Modifications [Line Items]
Total Modification
Individuals' loans for household and other personal expenditures | Rate Modification
Financing Receivable, Modifications [Line Items]
Total Modification	$ 14	9
Individuals' loans for household and other personal expenditures | Combination
Financing Receivable, Modifications [Line Items]
Total Modification

Loans and Allowance - Subsequen

Loans and Allowance - Subsequent Default (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Impaired [Line Items]
Number of Loans | loan	5	6
Recorded Balance | $	$ 337	$ 1,265
Commercial and industrial loans
Financing Receivable, Impaired [Line Items]
Number of Loans | loan		3
Recorded Balance | $		$ 197
Agriculture production financing and other loans to farmers
Financing Receivable, Impaired [Line Items]
Number of Loans | loan		1
Recorded Balance | $		$ 661
Commercial and farmland
Financing Receivable, Impaired [Line Items]
Number of Loans | loan	1	1
Recorded Balance | $	$ 14	$ 343
Residential
Financing Receivable, Impaired [Line Items]
Number of Loans | loan	4	1
Recorded Balance | $	$ 323	$ 64

Accounting for Certain Loans 82

Accounting for Certain Loans Acquired in a Purchase - Carrying Amount of Loans Included in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	$ 1,302,134	$ 698,097
Remaining fair value discount	(43,748)	(32,680)
Carrying amount	1,258,386	665,417
Allowance	769	380
Carrying amount net of allowance	1,257,617	665,037
IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	638,552
Remaining fair value discount	(20,090)
Carrying amount	618,462
Allowance	290
Carrying amount net of allowance	618,172
Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	186,099
Remaining fair value discount	(5,242)
Carrying amount	180,857
Carrying amount net of allowance	180,857
Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	183,339	250,824
Remaining fair value discount	(6,689)	(10,771)
Carrying amount	176,650	240,053
Allowance	411	265
Carrying amount net of allowance	176,239	239,788
C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	55,272	77,100
Remaining fair value discount	(1,266)	(1,906)
Carrying amount	54,006	75,194
Carrying amount net of allowance	54,006	75,194
Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	40,548	60,108
Remaining fair value discount	(2,482)	(4,101)
Carrying amount	38,066	56,007
Allowance	52	23
Carrying amount net of allowance	38,014	55,984
CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	175,958	279,479
Remaining fair value discount	(5,859)	(12,634)
Carrying amount	170,099	266,845
Allowance	16	92
Carrying amount net of allowance	170,083	266,753
SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	22,366	30,586
Remaining fair value discount	(2,120)	(3,268)
Carrying amount	20,246	27,318
Carrying amount net of allowance	20,246	27,318
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	103,530	37,236
Commercial and industrial loans | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	83,630
Commercial and industrial loans | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	3,152
Commercial and industrial loans | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	4,150	8,003
Commercial and industrial loans | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	64	85
Commercial and industrial loans | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	235	2,269
Commercial and industrial loans | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	10,539	23,327
Commercial and industrial loans | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	1,760	3,552
Agriculture production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	34,980	2,710
Agriculture production financing and other loans to farmers | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	33,537
Agriculture production financing and other loans to farmers | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance
Agriculture production financing and other loans to farmers | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	76	1,030
Agriculture production financing and other loans to farmers | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	50	50
Agriculture production financing and other loans to farmers | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	1,317	1,630
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	43,132	29,298
Construction | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	23,571
Construction | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	14,716
Construction | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	2,451	22,017
Construction | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	830	2,835
Construction | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	1,499	4,026
Construction | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	65	420
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	618,281	303,362
Commercial and farmland | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	346,155
Commercial and farmland | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	76,375
Commercial and farmland | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	79,739	103,075
Commercial and farmland | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	15,791	22,130
Commercial and farmland | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	27,910	36,947
Commercial and farmland | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	65,578	131,895
Commercial and farmland | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	6,733	9,315
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	377,459	257,640
Residential | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	100,569
Residential | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	69,011
Residential | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	86,098	103,414
Residential | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	32,854	44,101
Residential | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	6,354	9,363
Residential | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	79,674	96,627
Residential | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	2,899	4,135
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	107,463	64,819
Home equity | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	36,349
Home equity | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	22,581
Home equity | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	8,800	11,728
Home equity | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	5,733	7,947
Home equity | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	4,392	6,326
Home equity | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	19,972	26,894
Home equity | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	9,636	11,924
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	4,207	1,142
Individuals' loans for household and other personal expenditures | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	3,552
Individuals' loans for household and other personal expenditures | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	174
Individuals' loans for household and other personal expenditures | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	356	762
Individuals' loans for household and other personal expenditures | C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance		2
Individuals' loans for household and other personal expenditures | Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	82	147
Individuals' loans for household and other personal expenditures | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	22	201
Individuals' loans for household and other personal expenditures | SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	21	30
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	13,082	1,890
Other commercial loans | IAB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	11,189
Other commercial loans | Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	90
Other commercial loans | Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	1,745	1,825
Other commercial loans | CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	$ 58	$ 65

Accounting for Certain Loans 83

Accounting for Certain Loans Acquired in a Purchase - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance amount of loans acquired	$ 1,302,134,000	$ 698,097,000
Carrying amount of loans acquired	1,257,617,000	665,037,000
Loans acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance amount of loans acquired	38,900,000	60,500,000
Carrying amount of loans acquired	25,300,000	43,200,000
Allowance for loan losses and provision expense	$ 0	0
Loans acquired with deteriorated credit quality | Transferred to Other Real Estate Owned
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance amount of loans acquired		12,100,000
Carrying amount of loans acquired		$ 7,600,000
Loans transferred to Other Real Estate Owned, number | loan		1

Accounting for Certain Loans 84

Accounting for Certain Loans Acquired in a Purchase - Accretable Yield or Income Expected to be Collected (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	$ 3,950	$ 5,612	$ 5,390
Additions	1,608		2,305
Accretion	(6,749)	(6,577)	(5,850)
Reclassification from nonaccretable	4,748	5,172	3,925
Disposals	(667)	(257)	(158)
Ending balance	2,890	3,950	5,612
IAB
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Additions	941
Accretion	(1,009)
Reclassification from nonaccretable	834
Ending balance	766
Arlington Bank
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Additions	667
Accretion	(314)
Reclassification from nonaccretable	164
Ending balance	517
Ameriana
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	1,629	2,160
Additions			2,160
Accretion	(2,983)	(311)
Reclassification from nonaccretable	1,805	12
Disposals		(232)
Ending balance	451	1,629	2,160
C Financial
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	73	114
Additions			145
Accretion	(260)	(123)	(31)
Reclassification from nonaccretable	187	82
Ending balance		73	114
Community
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	1,233	1,508	2,122
Accretion	(454)	(1,119)	(723)
Reclassification from nonaccretable	212	858	249
Disposals	(122)	(14)	(140)
Ending balance	869	1,233	1,508
CFS
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	736	1,188	2,400
Accretion	(1,172)	(4,268)	(4,050)
Reclassification from nonaccretable	1,075	3,827	2,854
Disposals	(545)	(11)	(16)
Ending balance	94	736	1,188
SCB
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	279	642	868
Accretion	(557)	(756)	(1,046)
Reclassification from nonaccretable	471	393	822
Disposals			(2)
Ending balance	$ 193	$ 279	$ 642

Accounting for Certain Loans 85

Accounting for Certain Loans Acquired in a Purchase - Contractually Required Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 14, 2017	May 19, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments receivable at acquisition date	$ 20,314
Nonaccretable difference	11,243
Expected cash flows at acquisition date	9,071
Accretable difference	1,608
Basis in loans at acquisition date	7,463
IAB
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments receivable at acquisition date	14,131	$ 14,131
Nonaccretable difference	8,352
Expected cash flows at acquisition date	5,779
Accretable difference	941
Basis in loans at acquisition date	4,838	$ 4,838
Arlington Bank
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually required payments receivable at acquisition date	6,183		$ 6,183
Nonaccretable difference	2,891
Expected cash flows at acquisition date	3,292
Accretable difference	667
Basis in loans at acquisition date	$ 2,625		$ 2,625

Premises and Equipment - Summar

Premises and Equipment - Summary of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment [Line Items]
Total Cost	$ 228,827	$ 205,026
Accumulated Depreciation and Amortization	(132,975)	(110,594)
Net	95,852	94,432
Land
Premises and Equipment [Line Items]
Total Cost	22,042	25,035
Buildings and Leasehold Improvements
Premises and Equipment [Line Items]
Total Cost	124,441	114,444
Equipment
Premises and Equipment [Line Items]
Total Cost	$ 82,344	$ 65,547

Premises and Equipment - Narrat

Premises and Equipment - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 14, 2017	May 19, 2017
Premises and Equipment [Line Items]
Rent expense	$ 4,072	$ 4,586	$ 3,456
IAB
Premises and Equipment [Line Items]
Premises and equipment acquired				$ 10,107
Arlington Bank
Premises and Equipment [Line Items]
Premises and equipment acquired					$ 1,986

Premises and Equipment - Schedu

Premises and Equipment - Schedule of Future Minimum Rental Payments for Operating Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Property, Plant and Equipment [Abstract]
2,018	$ 3,161
2,019	3,611
2,020	3,484
2,021	3,137
2,022	3,090
After 2,022	15,180
Total Future Minimum Obligations	$ 31,663

Goodwill - Narrative (Details)

Goodwill - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Jul. 14, 2017	May 19, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill			$ 445,355,000	$ 244,000,000			$ 243,129,000
Measurement period adjustment			(469,000)	871,000
Goodwill impairment loss			$ 0	$ 0
IAB
Business Acquisition [Line Items]
Goodwill					$ 153,636,000
Arlington Bank
Business Acquisition [Line Items]
Goodwill						$ 47,719,000
Measurement period adjustment	$ 469,000
Merger with Ameriana Bancorp
Business Acquisition [Line Items]
Goodwill							$ 38,624,000
Measurement period adjustment		$ 871,000

Goodwill - Rollforward (Details

Goodwill - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 244,000	$ 243,129
Goodwill acquired	201,824
Measurement period adjustment	(469)	871
Ending balance	$ 445,355	$ 244,000

Other Intangibles - Narrative (

Other Intangibles - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 14, 2017	May 19, 2017
Business Acquisition [Line Items]
Measurement period adjustment			$ 2,142
Intangible asset amortization		$ 5,647	$ 3,910	$ 2,835
IAB
Business Acquisition [Line Items]
Core deposit intangible					$ 17,403
Arlington Bank
Business Acquisition [Line Items]
Core deposit intangible						$ 4,526
Merger with Ameriana Bancorp
Business Acquisition [Line Items]
Measurement period adjustment	$ 2,142
Core deposits | IAB
Business Acquisition [Line Items]
Core deposit intangible					13,638
Core deposits | Arlington Bank
Business Acquisition [Line Items]
Core deposit intangible						$ 4,526
Core deposits | Merger with Ameriana Bancorp
Business Acquisition [Line Items]
Core deposit intangible				$ 5,342
Noncompete agreements | IAB
Business Acquisition [Line Items]
Core deposit intangible					$ 3,765

Other Intangibles - Schedule of

Other Intangibles - Schedule of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 63,940	$ 61,798
Measurement period adjustment		2,142
Accumulated amortization	(54,721)	(49,074)
Core deposit intangible and other intangibles reduction
Core Deposit and Other Intangibles	31,148	14,866
Core deposits
Acquired Finite-Lived Intangible Assets [Line Items]
Intangibles acquired	18,164
Other intangible
Acquired Finite-Lived Intangible Assets [Line Items]
Intangibles acquired	$ 3,765

Other Intangibles - Schedule 93

Other Intangibles - Schedule of Estimated Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortization Expense
2,018	$ 6,719
2,019	5,169
2,020	3,632
2,021	3,427
2,022	3,325
After 2,022	8,876
Core Deposit and Other Intangibles	$ 31,148	$ 14,866

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Banking and Thrift [Abstract]
Demand deposits	$ 3,746,654	$ 2,866,853
Savings deposits	1,994,366	1,560,752
Certificates and other time deposits of $100,000 or more	468,895	276,274
Other certificates and time deposits	581,894	471,247
Brokered deposits	380,721	381,372
Total Deposits	7,172,530	5,556,498
Cash amount that exceeded federally insured limits	$ 3,200,000	$ 2,200,000

Deposits - Schedule of Contract

Deposits - Schedule of Contractual Maturities of Time Deposits (Details) $ in Thousands	Dec. 31, 2017USD ($)
Certificates and Other Time Deposits
2,018	$ 876,126
2,019	330,892
2,020	119,066
2,021	63,005
2,022	27,518
After 2,022	14,903
Total	$ 1,431,510

Transfers Accounted for as Se96

Transfers Accounted for as Secured Borrowings (Details) - U.S. Government-sponsored mortgage-backed securities - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	$ 136,623	$ 146,480
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	126,187	129,617
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	1,340	1,337
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	1,500	10,253
Greater Than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Collateral pledged for all repurchase agreements accounted for as secured borrowings	$ 7,596	$ 5,273

Borrowings - Schedule of Debt (

Borrowings - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Federal funds purchased	$ 144,038	$ 120,349
Securities sold under repurchase agreements	136,623	146,480
Federal Home Loan Bank advances	414,377	298,923
Subordinated debentures and term loans	139,349	128,445
Total Borrowings	$ 834,387	$ 694,197

Borrowings - Narrative (Details

Borrowings - Narrative (Details)	Jul. 14, 2017USD ($)	Aug. 10, 2015USD ($)	Nov. 01, 2013USD ($)investor	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 15, 2012	Jul. 02, 2007USD ($)
Debt Instrument [Line Items]
Total available remaining borrowing capacity from FHLB				$ 664,177,000
Puttable advances with the FHLB				414,377,000	$ 298,923,000
Debt face amount			$ 70,000,000
Gain from cancellation of debt						$ 1,250,000
Private debt issuance, number of institutional investors | investor			4
5.00% Senior Notes Due 2028
Debt Instrument [Line Items]
Redemption price (percent)				100.00%
5% Senior Notes Due 2028 and 6.75% Subordinated Notes due 2028
Debt Instrument [Line Items]
Debt term with fixed interest rate			10 years
Putable Advances
Debt Instrument [Line Items]
Puttable advances with the FHLB				$ 45,000,000
Minimum
Debt Instrument [Line Items]
Required value of assets pledged as collateral as a percentage to outstanding advances				142.00%
Interest rate, minimum (as a percent)				0.88%
Maximum
Debt Instrument [Line Items]
Interest rate, minimum (as a percent)				5.86%
Securities Sold Under Repurchase Agreements
Debt Instrument [Line Items]
Maximum amount of outstanding agreements				$ 145,883,000	158,185,000
Total of average agreements				134,401,000	145,379,000
Debt outstanding				136,623,000
Subordinated Debentures and Term Loans
Debt Instrument [Line Items]
Debt outstanding				$ 139,349,000	$ 128,445,000
Subordinated Debenture | 6.75% Subordinated Notes Due 2028
Debt Instrument [Line Items]
Debt face amount			$ 65,000,000
Interest rate on notes (as a percent)			6.75%
Redemption price (percent)				100.00%
Subordinated Debenture | Three-Month LIBOR | 6.75% Subordinated Notes Due 2028
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				4.095%
Subordinated Debenture | First Merchant Capital Trust II
Debt Instrument [Line Items]
Debt outstanding				$ 51,702,000
Debt face amount								$ 56,702,000
Cancellation of debt, amount		$ 5,000,000
Gain from cancellation of debt		$ 1,250,000
Interest rate on notes (as a percent)				3.15%	2.52%		6.495%
Subordinated Debenture | First Merchant Capital Trust II | Three-Month LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				1.56%
Subordinated Debenture | Ameriana Capital Trust I
Debt Instrument [Line Items]
Debt face amount						$ 10,310,000
Interest rate on notes (as a percent)				3.09%	2.46%
Basis spread on variable rate (as a percent)						1.50%
Subordinated Debenture | Grabill Capital Trust I
Debt Instrument [Line Items]
Debt face amount	$ 10,310,000
Interest rate on notes (as a percent)				3.96%
Basis spread on variable rate (as a percent)	2.60%
Senior Notes | 5.00% Senior Notes Due 2028
Debt Instrument [Line Items]
Debt face amount			$ 5,000,000
Interest rate on notes (as a percent)			5.00%
Senior Notes | Three-Month LIBOR | 5.00% Senior Notes Due 2028
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				2.345%

Borrowings - Schedule of Maturi

Borrowings - Schedule of Maturities of Long Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Federal Funds Purchased
Maturities in Years Ending December 31:
2,018	$ 144,038
Total	144,038
Securities Sold Under Repurchase Agreements
Maturities in Years Ending December 31:
2,018	136,623
Total	136,623
Federal Home Loan Bank Advances
Maturities in Years Ending December 31:
2,018	171,391
2,019	121,713
2,020	41,273
2,021	25,000
2,022	20,000
After 2,022	35,000
Total	414,377
Subordinated Debentures and Term Loans
Maturities in Years Ending December 31:
2,018
After 2,022	143,430
ASC 805 fair value adjustments at acquisition	(4,081)
Total	$ 139,349	$ 128,445

Derivative Instruments and H100

Derivative Instruments and Hedging Activities - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)interest_rate_swapinterest_rate_cap	Dec. 31, 2016USD ($)interest_rate_swapinterest_rate_cap
Derivative [Line Items]
Termination value of derivatives in a net liability position	$ 2,579
Derivative collateral posted	11,866
Not Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of interest rate derivatives	396,206
Cash Flow Hedging
Derivative [Line Items]
Estimated amount to be transferred from OCI to earnings	$ 640
Interest Rate Swap
Derivative [Line Items]
Number of interest rate derivatives held | interest_rate_swap	5	5
Notional amount of interest rate derivatives	$ 56,000	$ 56,000
Interest Rate Swap | Cash Flow Hedging | Trust Preferred Debt
Derivative [Line Items]
Notional amount of interest rate derivatives	26,000
Interest Rate Swap | Cash Flow Hedging | Federal Home Loan Bank Advances
Derivative [Line Items]
Notional amount of interest rate derivatives	$ 30,000
Interest Rate Cap
Derivative [Line Items]
Number of interest rate derivatives held | interest_rate_cap	1	1
Notional amount of interest rate derivatives	$ 13,000	$ 13,000
Interest Rate Cap | Cash Flow Hedging | Trust Preferred Debt
Derivative [Line Items]
Notional amount of interest rate derivatives	$ 13,000

Derivative Instruments and H101

Derivative Instruments and Hedging Activities - Fair Value of Derivative Financial Instruments and Their Classification on Balance Sheet (Details) - Interest Rate Contracts - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 18	$ 15
Derivatives Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	1,383	2,182
Derivatives Not Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	7,305	6,295
Derivatives Not Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 7,305	$ 6,295

Derivative Instruments and H102

Derivative Instruments and Hedging Activities - Effect of Derivative Financial Instruments on Income Statement (Details) - Interest Rate Contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives Designated as Hedging Instruments | Interest expense
Derivative [Line Items]
Amount of Loss Reclassified from Other Comprehensive Income Into Income (Effective Portion)	$ (985)	$ (1,250)	$ (1,427)
Derivatives Designated as Hedging Instruments | Cash Flow Hedging
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)	13	(368)
Not Designated as Hedging Instruments | Other income
Derivative [Line Items]
Amount of Gain (Loss) Recognized Income on Derivative	$ 0	$ 211	$ (53)

Fair Values of Financial Ins103

Fair Values of Financial Instruments - Fair Value Measurements of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	$ 999,947	$ 696,862
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		18,765
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	995,969	672,928
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	3,978	5,169
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		18,765
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swap liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap liability	8,688	8,477
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government-sponsored agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		100
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	522,750	358,524
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government-sponsored mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	470,866	312,292
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,353	2,012
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swap asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	7,305	6,295
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate cap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	18	15
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	3,943	5,134
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	31	31
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4	4
Fair Value, Measurements, Recurring | Fair Value | Interest rate swap liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap liability	8,688	8,477
Fair Value, Measurements, Recurring | Fair Value | U.S. Government-sponsored agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale		100
Fair Value, Measurements, Recurring | Fair Value | State and municipal
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	526,693	363,658
Fair Value, Measurements, Recurring | Fair Value | U.S. Government-sponsored mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	470,866	312,292
Fair Value, Measurements, Recurring | Fair Value | Corporate obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	31	31
Fair Value, Measurements, Recurring | Fair Value | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,357	20,781
Fair Value, Measurements, Recurring | Fair Value | Interest rate swap asset
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	7,305	6,295
Fair Value, Measurements, Recurring | Fair Value | Interest rate cap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	$ 18	$ 15

Fair Values of Financial Ins104

Fair Values of Financial Instruments - Reconciliation of Beginning and Ending Balances of Recurring Fair Value Measurements using Significant Unobservable Level 3 Inputs (Details) - Fair Value, Measurements, Recurring - Available for Sale Securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Available for Sale Securities
Beginning Balance	$ 5,169	$ 5,932
Included in other comprehensive income	26	(223)
Principal payments	(1,217)	(540)
Ending balance	$ 3,978	$ 5,169

Fair Values of Financial Ins105

Fair Values of Financial Instruments - Transfer Between Levels 1, 2 and 3 and Reasons for Transfers (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Transfer between in or out of Level 3	$ 0	$ 0

Fair Values of Financial Ins106

Fair Values of Financial Instruments - Valuation Methodologies Used for Instruments Measured at Fair Value on Non-Recurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Significant Unobservable Inputs (Level 3) | Impaired Loans (collateral dependent)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	$ 9,576	$ 15,318
Significant Unobservable Inputs (Level 3) | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	859	1,612
Fair Value | Impaired Loans (collateral dependent)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	9,576	15,318
Fair Value | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset fair value	$ 859	$ 1,612

Fair Values of Financial Ins107

Fair Values of Financial Instruments - Unobservable Inputs Used in Recurring and Nonrecurring Level 3 Fair Value Measurements Other Than Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Discounted cash flow | State and municipal securities
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 3,943	$ 5,134
Discounted cash flow | State and municipal securities | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Maturity Call Date	1 month	1 month
US Muni BQ curve	A-	A-
Discount rate	0.69%	0.69%
Discounted cash flow | State and municipal securities | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Maturity Call Date	20 years	20 years
US Muni BQ curve	BBB-	BBB-
Discount rate	5.00%	5.00%
Discounted cash flow | Corporate obligations and Equity securities
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 35	$ 35
Discounted cash flow | Corporate obligations and Equity securities | Three-Month LIBOR
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Premium for illiquidity (percent)	2.00%	2.00%
Collateral based measurements | Impaired loans (collateral dependent)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 9,576	$ 15,318
Collateral based measurements | Impaired loans (collateral dependent) | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability (percent)	0.00%	0.00%
Collateral based measurements | Impaired loans (collateral dependent) | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability (percent)	10.00%	10.00%
Collateral based measurements | Impaired loans (collateral dependent) | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability (percent)	1.00%	1.00%
Appraisals | Other real estate owned
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value	$ 859	$ 1,612
Appraisals | Other real estate owned | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	0.00%	0.00%
Appraisals | Other real estate owned | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	10.00%	10.00%
Appraisals | Other real estate owned | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	2.00%	9.00%

Fair Values of Financial Ins108

Fair Values of Financial Instruments - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Investment securities available for sale	$ 999,947	$ 696,862
Investment securities held to maturity	568,208	611,933
Loans held for sale	7,216	2,929
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	154,905	127,927
Interest-bearing time deposits	35,027	24,459
Investment securities available for sale		18,765
Liabilities:
Deposits	5,741,019	4,427,605
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	995,969	672,928
Investment securities held to maturity	556,305	597,246
Loans held for sale	7,216	2,929
Federal Home Loan Bank stock	23,825	17,964
Interest rate swap asset	7,323	6,310
Interest receivable	37,130	26,194
Liabilities:
Deposits	1,406,526	1,111,491
Borrowings:
Federal funds purchased	144,038	120,349
Securities sold under repurchase agreements	136,562	146,449
Federal Home Loan Bank advances	361,085	297,465
Subordinated debentures and term loans	120,085	105,930
Interest rate swap liability	8,688	8,477
Interest payable	4,390	3,110
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	3,978	5,169
Investment securities held to maturity	11,903	14,687
Loans	6,534,877	4,933,552
Carrying Amount
Assets:
Cash and cash equivalents	154,905	127,927
Interest-bearing time deposits	35,027	24,459
Investment securities available for sale	999,947	696,862
Investment securities held to maturity	560,655	607,643
Loans held for sale	7,216	2,929
Loans	6,676,167	5,073,608
Federal Home Loan Bank stock	23,825	17,964
Interest rate swap asset	7,323	6,310
Interest receivable	37,130	26,194
Liabilities:
Deposits	7,172,530	5,556,498
Borrowings:
Federal funds purchased	144,038	120,349
Securities sold under repurchase agreements	136,623	146,480
Federal Home Loan Bank advances	414,377	298,923
Subordinated debentures and term loans	139,349	128,445
Interest rate swap liability	8,688	8,477
Interest payable	$ 4,390	$ 3,110

Commitments and Contingent L109

Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loan commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Amounts of commitments	$ 2,482,641	$ 2,057,878
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Amounts of commitments	$ 43,526	$ 46,010

Accumulated Other Comprehens110

Accumulated Other Comprehensive Income (Loss) - Summary of Changes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 901,657	$ 850,509	$ 726,827
Other comprehensive income before reclassifications	12,340	(9,797)
Amounts reclassified from accumulated other comprehensive income	(1,667)	(2,422)	(1,006)
Period change	10,673	(12,219)	268
Ending balance	1,303,463	901,657	850,509
Total
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(13,581)	(1,362)	(1,630)
Period change	10,673	(12,219)	268
Ending balance	(2,908)	(13,581)	(1,362)
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	1,035	12,325
Other comprehensive income before reclassifications	9,645	(9,087)
Amounts reclassified from accumulated other comprehensive income	(1,710)	(2,203)	(1,736)
Period change	7,935	(11,290)
Ending balance	8,970	1,035	12,325
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(1,774)	(2,347)
Other comprehensive income before reclassifications	9	(240)
Amounts reclassified from accumulated other comprehensive income	640	813	928
Period change	649	573
Ending balance	(1,125)	(1,774)	(2,347)
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(12,842)	(11,340)
Other comprehensive income before reclassifications	2,686	(470)
Amounts reclassified from accumulated other comprehensive income	(597)	(1,032)
Period change	2,089	(1,502)
Ending balance	$ (10,753)	$ (12,842)	$ (11,340)

Accumulated Other Comprehens111

Accumulated Other Comprehensive Income (Loss) - Reclassifications (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Realized securities gains reclassified into income									$ 2,631	$ 3,389	$ 2,670
Income tax expense	$ (15,210)	$ (7,939)	$ (7,207)	$ (7,168)	$ (7,850)	$ (7,469)	$ (6,716)	$ (5,574)	(37,524)	(27,609)	(25,665)
Subordinated debentures and term loans									7,572	7,185	6,661
Salaries and employee benefits									119,812	102,552	101,908
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									1,667	2,422	1,006
Unrealized gains (losses) on available for sale securities
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									1,710	2,203	1,736
Unrealized gains (losses) on cash flow hedges
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									(640)	(813)	(928)
Unrealized gains (losses) on defined benefit plans
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									597	1,032
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on available for sale securities
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Realized securities gains reclassified into income									2,631	3,389	2,670
Income tax expense									(921)	(1,186)	(934)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on cash flow hedges
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense									345	437	499
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on cash flow hedges | Interest Rate Contracts
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Subordinated debentures and term loans									(985)	(1,250)	(1,427)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Unrealized gains (losses) on defined benefit plans
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense									(209)	(556)	(107)
Salaries and employee benefits									806	1,588	305
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									$ 597	$ 1,032	$ 198

Regulatory Capital and Divid112

Regulatory Capital and Dividends - Schedule of Actual and Required Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Total Risk-Based Capital
Actual	$ 1,048,757	$ 851,521
Prompt Corrective Action Thresholds, Adequate Capital	612,848	479,470
Tier 1 Capital to Risk-weighted Assets, Amount
Actual	908,725	720,484
Prompt Corrective Action Thresholds, Adequate Capital	459,636	359,603
Common Equity Tier One Capital to Risk-weighted Assets, Amount
Actual	842,806	665,445
Prompt Corrective Action Thresholds, Adequate Capital	344,727	269,702
Tier I Capital to Average Assets, Amount
Actual	908,725	720,484
Prompt Corrective Action Thresholds, Adequate Capital	$ 348,407	$ 273,456
Risk Based Ratios
Total Capital to Risk-weighted Assets, Actual Ratio	13.69%	14.21%
Total Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets	11.86%	12.02%
Tier I Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	6.00%	6.00%
Common Equity Tier 1 Capital Ratio (Regulatory)	11.00%	11.10%
Common Equity Tier 1 Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequately Capitalized Ratio	4.50%	4.50%
Leverage Ratios
Tier 1 Capital to Average Assets	10.43%	10.54%
Tier I Capital to Average Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	4.00%	4.00%
First Merchants Bank
Total Risk-Based Capital
Actual	$ 1,016,355	$ 800,598
Prompt Corrective Action Thresholds, Adequate Capital	617,477	481,490
Prompt Corrective Action Thresholds, Well Capitalized	771,847	601,862
Tier 1 Capital to Risk-weighted Assets, Amount
Actual	941,323	734,561
Prompt Corrective Action Thresholds, Adequate Capital	463,108	361,117
Prompt Corrective Action Thresholds, Well Capitalized	617,477	481,490
Common Equity Tier One Capital to Risk-weighted Assets, Amount
Actual	941,323	734,561
Prompt Corrective Action Thresholds, Adequate Capital	347,331	270,838
Prompt Corrective Action Thresholds, Well Capitalized	501,700	391,210
Tier I Capital to Average Assets, Amount
Actual	941,323	734,561
Prompt Corrective Action Thresholds, Adequate Capital	347,794	272,461
Prompt Corrective Action Thresholds, Well Capitalized	$ 434,742	$ 340,576
Risk Based Ratios
Total Capital to Risk-weighted Assets, Actual Ratio	13.17%	13.30%
Total Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	8.00%	8.00%
Total Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Well Capitalized Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets	12.20%	12.20%
Tier I Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	6.00%	6.00%
Tier I Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Well Capitalized Ratio	8.00%	8.00%
Common Equity Tier 1 Capital Ratio (Regulatory)	12.20%	12.20%
Common Equity Tier 1 Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Adequately Capitalized Ratio	4.50%	4.50%
Common Equity Tier 1 Capital to Risk-weighted Assets, Prompt Corrective Action Thresholds, Well Capitalized Ratio	6.50%	6.50%
Leverage Ratios
Tier 1 Capital to Average Assets	10.83%	10.78%
Tier I Capital to Average Assets, Prompt Corrective Action Thresholds, Adequate Capital Ratio	4.00%	4.00%
Tier I Capital to Average Assets, Prompt Corrective Action Thresholds, Well Capitalized Ratio	5.00%	5.00%

Regulatory Capital and Divid113

Regulatory Capital and Dividends - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 09, 2016
Banking and Thrift [Abstract]
Dividends available	$ 154,949,000
Dividend reinvestment and stock purchase plan, stockholder's maximum amount of cash payments per quarter in purchase of common stock	$ 2,500
Stock repurchase program		$ 15,000,000

Loan Servicing (Details)

Loan Servicing (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Banking and Thrift [Abstract]
Unpaid balance of loans serviced for others	$ 549,618	$ 369,592	$ 312,204

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($)	Jan. 01, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of average closing price to be paid by employees			85.00%
Share-based compensation			$ 2,827,000	$ 2,600,000	$ 2,270,000
Estimated pre-vesting forfeiture rate (as a percent)			2.80%
Income tax benefit related to adoption of ASU 2016-09	$ 935,000
Aggregate intrinsic value of stock options exercised			$ 1,728,000	1,641,000
Stock options exercised			2,398,000	$ 2,602,000	$ 1,531,000
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchases through advance payroll deductions in a calendar year			$ 25,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option term			10 years
Stock options vesting percentage			100.00%
Unrecognized compensation expense		$ 0	$ 0
Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested period			6 months
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested period			2 years
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested period			3 years
Unrecognized compensation expense		6,090,000	$ 6,090,000
Unrecognized compensation expense expected recognition period			1 year 5 months 12 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		0	$ 0
Grant date fair value of ESPP options		$ 28,000

Share-Based Compensation - Comp

Share-Based Compensation - Components of Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	$ 2,827	$ 2,600	$ 2,270
Income tax expense (benefit)	(1,883)	(865)	(745)
Total share-based compensation expense, net of income taxes	944	1,735	1,525
Stock and ESPP Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	121	76	101
Income tax expense (benefit)	(322)	18	4
Total share-based compensation expense, net of income taxes	(201)	94	105
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax compensation expense	2,706	2,524	2,169
Income tax expense (benefit)	(1,561)	(883)	(749)
Total share-based compensation expense, net of income taxes	$ 1,145	$ 1,641	$ 1,420

Share-Based Compensation - Stoc

Share-Based Compensation - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Beginning balance (in shares)	260,211
Exercised (in shares)	(104,748)
Canceled (in shares)	(2,811)
Ending balance (in shares)	152,652	260,211
Vested and Expected to Vest, Number of Shares	152,652
Exercisable, Number of Shares	152,652
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 19.26	$ 19.99
Exercised (in dollars per share)	22.90
Canceled (in dollars per share)	22.21
Ending balance (in dollars per share)	16.71	$ 19.26
Vested and Expected to Vest, Weighted-Average Exercise Price (in dollars per share)	16.71
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 16.71
Weighted Average Remaining Contractual Term
Outstanding	2 years 4 months 11 days
Vested and Expected to Vest	2 years 4 months 11 days
Exercisable	2 years 4 months 11 days
Aggregate Intrinsic Value
Outstanding	$ 3,870,499
Vested and Expected to Vest	3,870,499
Exercisable	$ 3,870,499

Share-Based Compensation - Unve

Share-Based Compensation - Unvested RSAs Outstanding (Details) - RSAs	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Number of Shares
Unvested RSAs, Beginning Balance (in shares) | shares	328,347
Granted (in shares) | shares	132,710
Forfeited (in shares) | shares	(4,702)
Vested (in shares) | shares	(89,362)
Unvested RSAs, Ending Balance (in shares) | shares	366,993
Weighted-Average Grant Date Fair Value
Unvested RSAs, Beginning Balance (in dollars per share) | $ / shares	$ 22.87
Granted (in dollars per share) | $ / shares	40.47
Forfeited (in dollars per share) | $ / shares	23.63
Vested (in dollars per share) | $ / shares	20.53
Unvested RSAs, Ending Balance (in dollars per share) | $ / shares	$ 29.79

Pension and Other Post Retir119

Pension and Other Post Retirement Benefit Plans - Narrative (Details) - USD ($)	Nov. 20, 2015	Mar. 01, 2005	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Percentage of employees covered by plan			15.00%
Minimum participant attained age		55 years
Requisite service period (at least)		10 years
Percentage of the premiums paid by plan participants			100.00%
Release of benefit obligation for plan settlement			$ 4,600,000
Settlement charge			(3,803,000)
Settlement loss recognized			761,000
Accumulated benefit obligation			82,157,000	$ 84,090,000
Minimum required contribution in next fiscal year			$ 0
Requisite service period			1000 hours
Employer percentage contribution			2.00%
Vesting period			5 years
Expense recognized in the period			$ 3,691,000	3,441,000	$ 3,526,000
Curtailment gain			2,157,000
Obligations payable				54,000
Post retirement plan expense			(301,000)	(2,437,000)	(127,000)
Fair value of plan assets			85,213,000	83,557,000	$ 71,396,000
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			78,280,000	64,064,000
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			$ 6,933,000	$ 19,493,000
Contribution for first 3%
Defined Benefit Plan Disclosure [Line Items]
Amount of discretionary contributions made by employer to defined contribution plan, percent			100.00%
Maximum annual contribution percentage per employee			3.00%
Contribution after first 3%
Defined Benefit Plan Disclosure [Line Items]
Amount of discretionary contributions made by employer to defined contribution plan, percent			50.00%
Maximum annual contribution percentage per employee			3.00%
Ameriana | Pentegra Plan
Defined Benefit Plan Disclosure [Line Items]
Written notice of withdrawal, period	60 days
Minimum
Defined Benefit Plan Disclosure [Line Items]
Age of plan participants			55 years
Minimum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities			15 days	15 days
Maximum
Defined Benefit Plan Disclosure [Line Items]
Age of plan participants			65 years
Maximum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities			8 years 10 months	8 years 11 days
Weighted Average | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities			4 years 6 months 12 days	3 years 11 months 20 days

Pension and Other Post Retir120

Pension and Other Post Retirement Benefit Plans - Schedule of Changes in Benefit Obligation, and Plan Assets, Funded Status of the Plan, Assets and Liabilities Recognized in the Balance Sheets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 84,090	$ 71,747
Service cost	10	9	$ 55
Interest cost	3,353	3,273	3,087
Actuarial loss	3,686	2,679
Benefits paid	(5,179)	(5,263)
Plan settlements	(3,803)
Net transfers in from Ameriana acquisition		11,645
Benefit obligation at end of year	82,157	84,090	71,747
Change in Plan Assets:
Fair value of plan assets at beginning of year	83,557	71,396
Actual return on plan assets	9,968	6,959
Employer contributions	670	739
Benefits paid	(5,179)	(5,263)
Plan settlements	(3,803)
Ameriana acquisition		9,726
End of year	85,213	83,557	$ 71,396
Funded status at end of year	3,056	(533)
Assets and Liabilities Recognized in the Balance Sheets:
Deferred tax asset	3,474	7,041
Assets	7,660	5,028
Liabilities	4,604	5,561
Amounts Recognized in Accumulated Other Comprehensive Income Not Yet Recognized as Components of Net Periodic Cost, net of tax, consist of:
Accumulated loss	(10,360)	(12,624)
Prior service cost	(393)	(451)
Total	$ (10,753)	$ (13,075)

Pension and Other Post Retir121

Pension and Other Post Retirement Benefit Plans - Schedule of Accumulated Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Projected benefit obligation	$ 4,604	$ 5,561
Accumulated benefit obligation	4,604	5,561
Fair value of plan assets	$ 0	$ 0

Pension and Other Post Retir122

Pension and Other Post Retirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Service cost	$ 10	$ 9	$ 55
Interest cost	3,353	3,273	3,087
Expected return on plan assets	(4,778)	(4,508)	(4,471)
Amortization of prior service costs	90	79	64
Amortization of net loss	1,218	1,656	1,722
Settlement loss recognized	761
Net periodic pension cost	$ 654	$ 509	$ 457

Pension and Other Post Retir123

Pension and Other Post Retirement Benefit Plans - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Net periodic pension cost	$ 654	$ 509	$ 457
Amortization of loss	1,504	(228)	1,299
Other Comprehensive (Income) Loss, Defined Benefit Plan, Amortization Cost (Credit), before Tax	1,979	1,656	1,722
Amortization of prior service cost	90	79	64
Total recognized in other comprehensive income	3,573	1,507	3,085
Total recognized in net periodic pension cost and other comprehensive income	$ 2,919	$ 998	$ 2,628

Pension and Other Post Retir124

Pension and Other Post Retirement Benefit Plans - Amount To Be Amortized From Accumulated Other Comprehensive Income, Next Fiscal Year (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amortization of net loss	$ (830)	$ (1,208)	$ (1,505)
Amortization of prior service cost	(87)	(90)	(61)
Total	$ (917)	$ (1,298)	$ (1,566)

Pension and Other Post Retir125

Pension and Other Post Retirement Benefit Plans - Schedule of Weighted Average Assumptions Used to Determine Benefit Obligation and Benefit Cost (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted-average Assumptions Used to Determine Benefit Obligation:
Discount rate	3.60%	4.20%	4.50%
Rate of compensation increase for accruing active participants		3.00%	3.00%
Weighted-average Assumptions Used to Determine Cost:
Discount rate	4.20%	4.50%	4.00%
Expected return on plan assets	6.00%	6.00%	6.00%
Rate of compensation increase for accruing active participants		3.00%	3.00%

Pension and Other Post Retir126

Pension and Other Post Retirement Benefit Plans - Schedule of Expected Future Benefit Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
2,018	$ 5,586
2,019	5,641
2,020	5,609
2,021	5,476
2,022	5,377
After 2,022	25,652
Total	$ 53,341

Pension and Other Post Retir127

Pension and Other Post Retirement Benefit Plans - Schedule of Plan Assets by Category (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	100.00%	100.00%
Target (as a percent)	100.00%	100.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	6.00%	4.50%
Target (as a percent)	3.00%	3.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	52.40%	55.80%
Target (as a percent)	55.00%	55.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	39.60%	37.70%
Target (as a percent)	40.00%	40.00%
Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Actual (as a percent)	2.00%	2.00%
Target (as a percent)	2.00%	2.00%

Pension and Other Post Retir128

Pension and Other Post Retirement Benefit Plans - Schedule of Plan Assets by Level (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 85,213	$ 83,557	$ 71,396
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	78,280	64,064
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,123	3,778
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate Bonds and Notes
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14,598	10,646
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,545	2,278
Quoted Prices in Active Markets for Identical Assets (Level 1) | Taxable Bond
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	12,198	7,974
Quoted Prices in Active Markets for Identical Assets (Level 1) | Large Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	22,137	19,611
Quoted Prices in Active Markets for Identical Assets (Level 1) | Mid Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,676	10,304
Quoted Prices in Active Markets for Identical Assets (Level 1) | Small Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,264	4,680
Quoted Prices in Active Markets for Identical Assets (Level 1) | International Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4,030	3,093
Quoted Prices in Active Markets for Identical Assets (Level 1) | Specialty Alternative Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,709	1,700
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	6,933	19,493
Significant Other Observable Inputs (Level 2) | Government Agency and Municipal Bonds and Notes
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,679	6,855
Significant Other Observable Inputs (Level 2) | Certificates of Deposit
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,254	1,268
Significant Other Observable Inputs (Level 2) | Common Bond Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		4,744
Significant Other Observable Inputs (Level 2) | Common Equity Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		6,626
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets
Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	85,213	83,557
Fair Value | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,123	3,778
Fair Value | Corporate Bonds and Notes
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14,598	10,646
Fair Value | Government Agency and Municipal Bonds and Notes
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,679	6,855
Fair Value | Certificates of Deposit
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,254	1,268
Fair Value | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,545	2,278
Fair Value | Common Bond Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		4,744
Fair Value | Common Equity Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		6,626
Fair Value | Taxable Bond
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	12,198	7,974
Fair Value | Large Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	22,137	19,611
Fair Value | Mid Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,676	10,304
Fair Value | Small Cap Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,264	4,680
Fair Value | International Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4,030	3,093
Fair Value | Specialty Alternative Equity
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 1,709	$ 1,700

Income Tax - Reconciliation of

Income Tax - Reconciliation of Federal Statutory to Actual Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal Statutory Income Tax at 35%									$ 46,758	$ 38,031	$ 31,867
Tax-exempt Interest Income									(11,127)	(8,749)	(7,083)
Basis Difference on Sale of Insurance Subsidiary											2,252
Stock Compensation									(893)	(61)	(31)
Earnings on Life Insurance									(2,302)	(1,486)	(1,012)
Tax Credits									(811)	(564)	(583)
Tax Cuts and Jobs Act - Rate Reform Impact									5,120
Other									779	438	255
Income Tax Expense	$ 15,210	$ 7,939	$ 7,207	$ 7,168	$ 7,850	$ 7,469	$ 6,716	$ 5,574	$ 37,524	$ 27,609	$ 25,665
Federal statutory income tax rate									35.00%	35.00%	35.00%

Income Tax - Components of Inco

Income Tax - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Currently Payable:
Federal									$ 22,001	$ 18,998	$ 21,221
Deferred:
Federal									9,969	8,233	3,952
Tax Cuts and Jobs Act - Rate Reform Impact									5,120
State									434	378	492
Income Tax Expense	$ 15,210	$ 7,939	$ 7,207	$ 7,168	$ 7,850	$ 7,469	$ 6,716	$ 5,574	$ 37,524	$ 27,609	$ 25,665

Income Tax - Deferred Tax Asset

Income Tax - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Assets:
Differences in Accounting for Loan Losses	$ 19,526	$ 26,315
Differences in Accounting for Loan Fees	1,458	1,918
Differences in Accounting for Loans and Securities	3,681	5,689
Deferred Compensation	4,448	3,471
Difference in Accounting for Pensions and Other Employee Benefits		83
Federal & State Income Tax Loss Carryforward and Credits	10,829	16,643
Other	365	4,210
Total Assets	40,307	58,329
Liabilities:
Differences in Depreciation Methods	5,245	8,216
Difference in Accounting for Pensions and Other Employee Benefits	823
State Income Tax	58	237
Net Unrealized Gain on Securities Available for Sale	2,898	557
Gain on FDIC Modified Whole Bank Transaction	602	1,126
Other	3,897	623
Total Liabilities	13,523	10,759
Net Deferred Tax Asset Before Valuation Allowance	26,784	47,570
Valuation allowance:
Beginning Balance	(9,815)	(15,736)
Decrease/(Increase) During the Year	2,849	5,921
Ending Balance	(6,966)	(9,815)
Net Deferred Tax Asset	$ 19,818	$ 37,755

Income Tax - Narrative (Details

Income Tax - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Decrease in deferred tax assets	$ 17,937,000
TCJA tax adjustment	5,120,000
Valuation allowance	6,966,000	$ 9,815,000	$ 15,736,000
Additional paid-in capital	834,870,000	$ 509,018,000
Unrecorded deferred tax liability	5,308,000
CFS
Valuation Allowance [Line Items]
Additional paid-in capital	13,393,000
Ameriana
Valuation Allowance [Line Items]
Additional paid-in capital	11,883,000
Federal
Valuation Allowance [Line Items]
Decrease in deferred tax assets for federal and state net operating loss carryforwards	2,323,000
State and Local Jurisdiction
Valuation Allowance [Line Items]
State tax loss carryforward	45,196,000
State deferred tax assets	7,400,000
Valuation allowance	6,966,000
Available for Sale Securities
Valuation Allowance [Line Items]
Decrease in deferred tax liability	4,273,000
Other employee benefits
Valuation Allowance [Line Items]
Decrease in deferred tax assets	2,080,000
Acquisitions
Valuation Allowance [Line Items]
Decrease in deferred tax liability	$ 4,106,000

Net Income Per Share - Reconcil

Net Income Per Share - Reconciliation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income available to common stockholders									$ 96,070	$ 81,051	$ 65,384
Net income available to common stockholders									$ 96,070	$ 81,051	$ 65,384
Weighted-Average Shares
Net income available to common stockholders (in shares)	49,144,310	48,431,880	42,038,824	40,984,481	40,846,650	40,779,423	40,751,720	40,690,573	45,181,221	40,767,343	37,816,399
Effect of dilutive stock options and warrants (in shares)									221,757	245,790	271,834
Net income available to common stockholders (in shares)	49,379,303	48,643,774	42,243,539	41,220,586	41,124,179	41,025,784	40,969,111	40,916,972	45,402,978	41,013,133	38,088,233
Basic net income per share:
Net income available to common stockholders (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.57	$ 0.55	$ 0.51	$ 0.50	$ 0.43	$ 2.13	$ 1.99	$ 1.73
Diluted net income per share:
Net income available to common stockholders (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.56	$ 0.55	$ 0.51	$ 0.49	$ 0.43	$ 2.12	$ 1.98	$ 1.72

Net Income Per Share - Narrativ

Net Income Per Share - Narrative (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Earnings Per Share [Abstract]
Stock options not included in the earnings per share calculation (in shares)	51,949	286,119
Weighted average exercise price (in dollars per share)	$ 19.26	$ 19.99	$ 16.71

Quarterly Results of Operati135

Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 90,348	$ 84,847	$ 71,467	$ 68,234	$ 65,005	$ 64,376	$ 62,704	$ 61,227	$ 314,896	$ 253,312	$ 221,198
Interest expense	11,583	10,427	8,367	7,235	6,631	6,694	6,742	6,772	37,612	26,839	24,794
NET INTEREST INCOME	78,765	74,420	63,100	60,999	58,374	57,682	55,962	54,455	277,284	226,473	196,404
Provision for loan losses	1,800	2,083	2,875	2,385	2,417	1,900	790	550	9,143	5,657	417
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	76,965	72,337	60,225	58,614	55,957	55,782	55,172	53,905	268,141	220,816	195,987
Non-interest income	19,061	18,668	18,434	14,846	16,120	16,861	16,385	15,837	71,009	65,203	69,868
Non-interest expense	56,433	58,708	47,316	43,099	41,934	44,115	44,835	46,475	205,556	177,359	174,806
INCOME BEFORE INCOME TAX	39,593	32,297	31,343	30,361	30,143	28,528	26,722	23,267
Income tax expense	15,210	7,939	7,207	7,168	7,850	7,469	6,716	5,574	37,524	27,609	25,665
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 24,383	$ 24,358	$ 24,136	$ 23,193	$ 22,293	$ 21,059	$ 20,006	$ 17,693	$ 96,070	$ 81,051	$ 65,384
Basic EPS (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.57	$ 0.55	$ 0.51	$ 0.50	$ 0.43	$ 2.13	$ 1.99	$ 1.73
Diluted EPS (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.56	$ 0.55	$ 0.51	$ 0.49	$ 0.43	$ 2.12	$ 1.98	$ 1.72
Average Shares Outstanding:
Basic (in shares)	49,144,310	48,431,880	42,038,824	40,984,481	40,846,650	40,779,423	40,751,720	40,690,573	45,181,221	40,767,343	37,816,399
Diluted (in shares)	49,379,303	48,643,774	42,243,539	41,220,586	41,124,179	41,025,784	40,969,111	40,916,972	45,402,978	41,013,133	38,088,233

Condensed Financial Informat136

Condensed Financial Information (parent company only) - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Investment securities	$ 999,947	$ 696,862
Premises and equipment	95,852	94,432
Interest receivable	37,130	26,194
Goodwill	445,355	244,000	$ 243,129
Cash surrender value of life insurance	223,557	201,671
Other assets	42,338	30,706
TOTAL ASSETS	9,367,478	7,211,611
Liabilities
Subordinated debentures and term loans	139,349	128,445
Interest payable	4,390	3,110
Other liabilities	52,708	56,149
Total Liabilities	8,064,015	6,309,954
Stockholders' equity	1,303,463	901,657	$ 850,509	$ 726,827
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	9,367,478	7,211,611
Parent
Assets
Cash	31,527	31,944
Investment in subsidiaries	1,411,360	978,291
Investment securities	31	18,765
Premises and equipment	1,252	1,260
Interest receivable	5	47
Goodwill	448	448
Cash surrender value of life insurance	787	1,082
Tax asset, deferred and receivable		521
Other assets	3,480	5,274
TOTAL ASSETS	1,448,890	1,037,632
Liabilities
Subordinated debentures and term loans	138,241	127,427
Interest payable	968	880
Other liabilities	6,218	7,668
Total Liabilities	145,427	135,975
Stockholders' equity	1,303,463	901,657
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,448,890	$ 1,037,632

Condensed Financial Informat137

Condensed Financial Information (parent company only) - Statement of Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income
Gain on the sale of insurance subsidiary											$ 8,265
Gain on cancellation of subordinated debentures											1,250
Net realized gains on sales of available for sale securities									2,631	3,389	2,670
Other income									2,970	3,594	1,778
Expenses
Interest expense	$ 11,583	$ 10,427	$ 8,367	$ 7,235	$ 6,631	$ 6,694	$ 6,742	$ 6,772	37,612	26,839	24,794
Salaries and employee benefits									119,812	102,552	101,908
Other expenses									15,543	15,470	15,187
INCOME BEFORE INCOME TAX	39,593	32,297	31,343	30,361	30,143	28,528	26,722	23,267
Income tax benefit (expense)	(15,210)	(7,939)	(7,207)	(7,168)	(7,850)	(7,469)	(6,716)	(5,574)	(37,524)	(27,609)	(25,665)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS									96,070	81,051	65,384
Net income	$ 24,383	$ 24,358	$ 24,136	$ 23,193	$ 22,293	$ 21,059	$ 20,006	$ 17,693	96,070	81,051	65,384
Other comprehensive income (loss)									10,673	(12,219)	268
Comprehensive income									106,743	68,832	65,652
Parent
Income
Dividends from subsidiaries									33,014	33,546	39,032
Gain on the sale of insurance subsidiary											8,265
Gain on cancellation of subordinated debentures											1,250
Net realized gains on sales of available for sale securities									(50)
Other income									350	143	197
Total income									33,314	33,689	48,744
Expenses
Interest expense									7,572	7,185	6,661
Salaries and employee benefits									4,118	639	3,023
Net occupancy and equipment expenses									797	832	464
Other outside services									1,810	967	1,455
Professional services									442	279	636
Other expenses									(385)	(470)	1,234
Total expenses									14,354	9,432	13,473
INCOME BEFORE INCOME TAX									18,960	24,257	35,271
Income tax benefit (expense)									5,946	3,243	(974)
Income before equity in undistributed income of subsidiaries									24,906	27,500	34,297
Equity in undistributed income of subsidiaries									71,164	53,551	31,087
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS									96,070	81,051	65,384
Net income									96,070	81,051	65,384
Other comprehensive income (loss)									10,673	(12,219)	268
Comprehensive income									$ 106,743	$ 68,832	$ 65,652

Condensed Financial Informat138

Condensed Financial Information (parent company only) - Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flow From Operating Activities:
Net income	$ 24,383	$ 24,358	$ 24,136	$ 23,193	$ 22,293	$ 21,059	$ 20,006	$ 17,693	$ 96,070	$ 81,051	$ 65,384
Adjustments to Reconcile Net Income to Net Cash:
Share-based compensation									2,827	2,600	2,270
Gain on sale of insurance subsidiary											(8,265)
Gain on cancellation of subordinated debentures											(1,250)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									(2,631)	(3,389)	(2,670)
Net Change in:
Net cash provided by operating activities									126,502	103,719	56,660
Cash Flows from Investing Activities:
Purchase of securities available for sale									(479,045)	(281,470)	(200,154)
Net cash received (paid) in acquisition									54,536		(7,936)
Other									(4,047)	(4,490)	9
Net cash used in investing activities									(635,330)	(448,704)	(340,391)
Cash Flows from Financing Activities:
Repayment of borrowings									(1,024,166)	(982,449)	(370,813)
Stock issued under employee benefit plans									519	462	460
Stock issued under dividend reinvestment and stock purchase plan									991	835	661
Stock options exercised									2,398	2,602	1,531
Stock redeemed									(1,283)	(1,980)	(1,640)
Net cash provided by financing activities									535,806	370,742	267,285
Cash and Cash Equivalents, beginning of the year				127,927				102,170	127,927	102,170	118,616
Cash and Cash Equivalents, end of year	154,905				127,927				154,905	127,927	102,170
Parent
Cash Flow From Operating Activities:
Net income									96,070	81,051	65,384
Adjustments to Reconcile Net Income to Net Cash:
Share-based compensation									1,215	1,166	843
Distributions in excess of (equity in undistributed) income of subsidiaries									(71,164)	(53,551)	(31,087)
Gain on sale of insurance subsidiary											(8,265)
Gain on cancellation of subordinated debentures											(1,250)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									50
Net Change in:
Other assets									3,358	833	(441)
Other liabilities									(1,900)	849	(1,486)
Investment in subsidiaries - operating activities									1,112	(1,938)	197
Net cash provided by operating activities									28,741	28,410	23,895
Cash Flows from Investing Activities:
Purchase of securities available for sale										(19,804)
Net cash received (paid) in acquisition									37		(14,500)
Proceeds from business divestitures											16,000
Other											575
Net cash used in investing activities									37	(19,804)	2,075
Cash Flows from Financing Activities:
Cash dividends									(31,820)	(22,203)	(15,654)
Repayment of borrowings											(3,750)
Stock issued under employee benefit plans									519	462	460
Stock issued under dividend reinvestment and stock purchase plan									991	835	661
Stock options exercised									2,398	2,602	1,531
Stock redeemed									(1,283)	(1,980)	(1,640)
Net cash provided by financing activities									(29,195)	(20,284)	(18,392)
Cash and Cash Equivalents, beginning of the year				$ 31,944				$ 43,622	31,944	43,622	36,044
Cash and Cash Equivalents, end of year	$ 31,527				$ 31,944				$ 31,527	$ 31,944	$ 43,622