| **Regulatory Capital (Tables)**                                                       | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
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| **Banking and Thrift [Abstract]**                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations | Actual and required capital amounts and ratios are listed below. 20142013   Required For  Required For ActualAdequate CapitalActualAdequate CapitalDecember 31,AmountRatioAmountRatioAmountRatioAmountRatioTotal Capital (to Risk-weighted Assets)        First Merchants Corporation$685,50715.34%$357,5818.00%$599,96614.54%$330,1078.00%First Merchants Bank653,16914.64356,8848.00599,27214.56329,3448.00Tier I Capital (to Risk-weighted Assets)     First Merchants Corporation$564,53512.63%$178,7914.00%$483,18611.71%$165,0534.00%First Merchants Bank597,30513.39178,4424.00547,65513.30164,6724.00Tier I Capital (to Average Assets)     First Merchants Corporation$564,53510.15%$222,5334.00%$483,18610.20%$189,4854.00%First Merchants Bank597,30510.56226,3394.00547,65511.58189,0954.00 |

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| - Definition
Tabular disclosure of the capital amounts and ratios as of the balance sheet date, indicating whether the entity or entities are in compliance with regulatory capital requirements, by entity.
+ References
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