| **Subsequent Events**            | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| **Subsequent Events [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Subsequent Events                | SUBSEQUENT EVENTSOn April 1, 2016, the Board of Directors of First Merchants Bank, National Association (the “Bank”), a wholly-owned subsidiary of First Merchants Corporation, 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 Department of Financial Institutions (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 Federal Deposit Insurance Corporation (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 intends to continue 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 is not expected to affect the Bank’s operations or customers in any way, and Bank customers will continue to receive identical protection on deposits through the FDIC’s deposit insurance program. |

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The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.
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