| **Borrowings**                 | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           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| **Debt Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    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| Borrowings                     | BORROWINGSThe following table summarizes the Corporation's borrowings as of December 31, 2016 and 2015:December 31, 2016December 31, 2015Federal funds purchased$120,349$49,721Securities sold under repurchase agreements146,480155,325Federal Home Loan Bank advances298,923235,652Subordinated debentures and term loans128,445127,846Total Borrowings$694,197$568,544 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 2016 and 2015 totaled $158,185,000 and $163,128,000, respectively, and the average of such agreements totaled $145,379,000 and $143,491,000 during 2016 and 2015, respectively.Contractual maturities of borrowings as of December 31, 2016, are as follows:Maturities in Years Ending December 31:Federal Funds Purchased Securities SoldUnder Repurchase Agreements Federal HomeLoan BankAdvances SubordinatedDebentures andTerm Loans2017$120,349 $146,480 $167,068 $1,0182018    26,717  2019    13,828  2020    31,310  2021    25,000  After 2021    35,000 132,012ASC 805 fair value adjustments at acquisition      (4,585) $120,349 $146,480 $298,923 $128,445The 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 0.60 to 6.81 percent, are subject to restrictions or penalties in the event of prepayment. The total available remaining borrowing capacity from the FHLB at December 31, 2016, was $291,445,000.  As of December 31, 2016, the Corporation had $25,000,000 of putable advances with the FHLB. Subordinated Debentures and Term Loans.  As of December 31, 2016 and 2015, subordinated debentures and term loans totaled $128,445,000 and 127,846,000, 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, 2016, $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, 2016 and 2015 was 2.52 percent and 2.07 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, 2016 and 2015 was 2.46 percent and 2.01 percent, respectively.  The Corporation holds all of the outstanding common securities of Ameriana 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, 2016 and 2015 the Corporation was in compliance with these covenants.Line of Credit.  As of December 31, 2016, the line of credit was no longer in place.  As of December 31, 2015, there was no outstanding balance on the line of credit.•On April 11, 2014 the Corporation entered into a line of credit agreement with U.S. Bank, N.A. with a maximum borrowing capacity of $20 million.  The line of credit matured on April 8, 2016 and the agreement was not renewed.  Interest was payable quarterly based on one-month LIBOR plus 2.00 percent.  The line of credit had a quarterly facility fee of 0.25 percent on the unused balance.  The line of credit agreement contained certain customary representations and warranties and financial and negative covenants. |

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| - References
No definition available.
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| - Definition
The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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