| **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, 2012 and 2011:December 31, 2012December 31, 2011Federal Funds Purchased$18,862Securities Sold Under Repurchase Agreements141,828$156,305Federal Home Loan Bank Advances94,238138,095Subordinated Debentures and Term Loans112,161194,974Total Borrowings$367,089$489,374 Securities sold under repurchase agreements consist of obligations of the Bank to other parties. The obligations are secured by U.S. Treasury and U.S. Government-Sponsored Enterprise obligations. The maximum amount of outstanding agreements at any month-end during 2012 and 2011 totaled $160,127,000 and $162,315,000, respectively, and the average of such agreements totaled $144,555,000 and $120,415,000 during 2012 and 2011, respectively.Included in the outstanding balance of Federal Home Loan Bank Advances are $0 and $48,000,000 of putable advances as of December 31, 2012 and 2011 respectively. Maturities of securities sold under repurchase agreements; Federal Home Loan Bank Advances, subordinated debentures and term loans as of December 31, 2012, are as follows:Maturities in Years Ending December 31:Securities SoldUnder Repurchase AgreementsFederal HomeLoan BankAdvancesSubordinatedDebentures andTerm Loans2013$131,828$1,619$459201410,00026,506201530,98655,000201628,93320172,731After 20173,46356,702 $141,828$94,238$112,161The terms of a security agreement with the FHLB require the Corporation to pledge, as collateral for advances, qualifying first mortgage loans, investment securities and multifamily loans in an amount equal to at least 155 percent of these advances depending on the type of collateral pledged. Advances, with interest rates from 0.86 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, 2012, was $217,275,000.Subordinated Debentures and Term Loans.  As of December 31, 2012, subordinated debentures and term loans totaled $112,161,000.•First Merchants Capital Trust II. The subordinated debenture, entered into on July 2, 2007, for $56,702,000 will mature on 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 Corporation holds all of the outstanding common securities of First Merchants Capital Trust II.•Bank of America, N.A. The Corporation currently has a $55 million credit facility with Bank of America, N.A. comprised of (a) a term loan in the principal amount of $5 million (the “Term Loan”) and (b) a subordinated debenture in the principal amount of $50 million (the “Subordinated Debt”).  Pursuant to the terms of the underlying Loan Agreement (the “Loan Agreement”), the Term Loan and the Subordinated Debt each mature on February 15, 2015.  The Term Loan is secured by a pledge of all of the issued and outstanding shares of the Bank. The Loan Agreement contains certain customary representations and warranties and financial and negative covenants.  A breach of any of these covenants could result in a default under the Loan Agreement.  As of December 31, 2012, the Corporation was in compliance with these financial covenants. The Loan Agreement provides that upon an event of default as the result of the Corporation’s failure to comply with a financial covenant, Bank of America may (a) declare the $5 million outstanding principal amount of the Term Loan immediately due and payable, (b) exercise all of its rights and remedies at law, in equity and/or pursuant to any or all collateral documents, including foreclosing on the collateral if payment of the Term Loan is not made in full, and (c) add a default rate of 3 percent per annum to the Term Loan.  Because the Subordinated Debt is treated as Tier 2 capital for regulatory capital purposes, the Loan Agreement does not provide Bank of America with any right of acceleration or other remedies with regard to the Subordinated Debt upon an event of default caused by the Corporation’s breach of a financial covenant.  Bank of America chose to apply the default rate through March 31, 2012 but not to accelerate the Term Loan based on the Corporation’s failure to meet these financial covenants. As of March 31, 2012, the Corporation was no longer in default due to breach of a financial covenant; therefore, the default rate of 3 percent per annum was no longer applied to the Term Loan.•CNBC Statutory Trust I. As part of the March 1, 2003, acquisition of CNBC Bancorp, the Corporation assumed $4,124,000 of a junior subordinated debenture entered into on February 22, 2001.  On August 22, 2012, the Corporation exercised its option to redeem the $4,124,000 subordinated debt. The redemption price premium was 104.59. The debenture carried a fixed interest rate of 10.2.•Temporary Liquidity Guarantee Program. On March 31, 2009, the Bank, entered into $79,000,000 of 2.625 percent Senior Notes (the “Notes”) due on March 30, 2012 through a pooled offering. On March 30, 2012, the Bank completed repayment of these Notes, which were guaranteed by the FDIC under its Temporary Liquidity Guarantee Program ("TLGP").Subordinated Debentures and Term Loans. As of December 31, 2011, subordinated debentures and term loans totaled $194,974,000.•First Merchants Capital Trust III. The Corporation entered into a junior subordinated debenture on June 30, 2010 for $47,835,000, subsequent to an Exchange Agreement with the United States Department of the Treasury (the "Treasury") whereby the Treasury exchanged 46,400 shares of the Corporation's Preferred Stock for 46,400 shares of trust preferred securities, issued by First Merchants Capital Trust III. The Trust used 46,400 shares of tendered preferred stock and $1.4 million in proceeds from the sale of Common Securities to the Corporation to purchase the debentures. On September 22, 2011, the Corporation redeemed the Capital Securities and Debentures pursuant to a Repurchase Letter agreement with the Treasury.  For more information related to this debt repayment, see Note 14.  Stockholders' Equity in the Notes to Consolidated Condensed Financial Statements of the 2011 Annual Report on Form 10-K.•First Merchants Capital Trust II. The subordinated debenture, entered into on July 2, 2007, for $56,702,000 will mature on September 15, 2037. The Corporation may redeem the debenture no earlier than September 15, 2012, subject to the prior approval of the Board of Governors of the Federal Reserve System, as required by law or regulation. Interest is fixed at 6.495 percent for the period from the date of issuance through September 15, 2012, and thereafter, at 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 Corporation holds all of the outstanding common securities of First Merchants Capital Trust II•CNBC Statutory Trust I. As part of the March 1, 2003 acquisition of CNBC Bancorp, the Corporation assumed $4,124,000 of a junior subordinated debenture entered into on February 22, 2001. The subordinated debenture of $4,124,000 will mature on February 22, 2031. Interest is fixed at 10.2 percent and payable on February 22 and August 22 of each year. The Corporation may redeem the debenture, in whole or in part, at its option commencing February 22, 2011, at a redemption price of 105.1 percent of the outstanding principal amount and, thereafter, at a premium which declines annually. On or after February 22, 2021, the securities may be redeemed at face value with prior approval of the Board of Governors of the Federal Reserve System. The Corporation holds all of the outstanding common securities of CNBC Statutory Trust I.•Bank of America, N.A. The Corporation currently has a $55 million credit facility with Bank of America, N.A. comprised of (a) a term loan in the principal amount of $5 million (the “Term Loan”) and (b) a subordinated debenture in the principal amount of $50 million (the “Subordinated Debt”).  Pursuant to the terms of the underlying Loan Agreement (the “Loan Agreement”), the Term Loan and the Subordinated Debt each mature on February 15, 2015.  The Term Loan is secured by a pledge of all of the issued and outstanding shares of the Bank. The Loan Agreement contains certain customary representations and warranties and financial and negative covenants.  A breach of any of these covenants could result in a default under the Loan Agreement. At December 31, 2011, the Corporation failed to meet the minimum return on average total assets covenant of 0.75 percent. The Loan Agreement provides that upon an event of default as the result of the Corporation’s failure to comply with a financial covenant, Bank of America may (a) declare the $5 million outstanding principal amount of the Term Loan immediately due and payable, (b) exercise all of its rights and remedies at law, in equity and/or pursuant to any or all collateral documents, including foreclosing on the collateral if payment of the Term Loan is not made in full, and (c) add a default rate of 3 percent per annum to the Term Loan.  Because the Subordinated Debt is treated as Tier 2 capital for regulatory capital purposes, the Loan Agreement does not provide Bank of America with any right of acceleration or other remedies with regard to the Subordinated Debt upon an event of default caused by the Corporation’s breach of a financial covenant.  To date, Bank of America has chosen to apply the default rate, but not to accelerate the Term Loan based on the Corporation’s failure to meet these financial covenants.•Temporary Liquidity Guarantee Program. On March 31, 2009, the Bank, entered into $79,000,000 of 2.625 percent Senior Notes (the “Notes”) due on March 30, 2012 through a pooled offering. Including the FDIC fee, underwriting, legal and accounting expenses, the effective rate is 3.812 percent. The Notes are guaranteed by the Federal Deposit Insurance Corporation under its Temporary Liquidity Guarantee Program and are backed by the full faith and credit of the United States. The Notes are issued by the Bank and are not an obligation of, or guaranteed by, the Corporation. In connection with the FDIC's Temporary Liquidity Guarantee Program, the Bank entered into a Master Agreement with the FDIC on January 16, 2009. The Master Agreement contains, among other things, certain terms and conditions that must be included in the governing documents for any senior debt securities issued by the Bank that is guaranteed pursuant to the FDIC's Temporary Liquidity Guarantee Program. |

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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 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20, 22 -Article 5Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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