| **Acquisitions and Divestitures - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands** | Mar. 31, 2016 | Dec. 31, 2015 | Apr. 17, 2015 | Mar. 31, 2015 | Dec. 31, 2014 |
|----------------------------------------------------------------------------------------------------------------|---------------|---------------|---------------|---------------|---------------|
| **Business Acquisition [Line Items]**                                                                          |          |          |          |          |          |
| Goodwill                                                                                                       | $ 244,000     | $ 243,129     |          | $ 202,724     | $ 202,724     |
| Ameriana                                                                                                       |          |          |          |          |          |
| **Business Acquisition [Line Items]**                                                                          |          |          |          |          |          |
| Cash and cash equivalents                                                                                      |          | 4,068         |          |          |          |
| Interest-bearing time deposits                                                                                 |          | 8,790         |          |          |          |
| Investment securities                                                                                          |          | 61,754        |          |          |          |
| Loans                                                                                                          |          | 316,929       |          |          |          |
| Premises and equipment                                                                                         |          | 13,946        |          |          |          |
| Federal Home Loan Bank stock                                                                                   |          | 2,693         |          |          |          |
| Other real estate owned                                                                                        |          | 5,613         |          |          |          |
| Interest receivable                                                                                            |          | 1,306         |          |          |          |
| Cash surrender value of life insurance                                                                         |          | 28,188        |          |          |          |
| Other assets                                                                                                   |          | 6,713         |          |          |          |
| Deposits                                                                                                       |          | (383,718)     |          |          |          |
| Interest payable                                                                                               |          | (24)          |          |          |          |
| Federal Home Loan Bank Advances                                                                                |          | (24,884)      |          |          |          |
| Subordinated debentures                                                                                        |          | (5,487)       |          |          |          |
| Other liabilities                                                                                              |          | (9,451)       |          |          |          |
| Net tangible assets acquired                                                                                   |          | 26,436        |          |          |          |
| Core deposit intangible                                                                                        |          | 5,342         |          |          |          |
| Goodwill                                                                                                       |          | 38,624        |          |          |          |
| Purchase price                                                                                                 |          | $ 70,402      |          |          |          |
| C Financial                                                                                                    |          |          |          |          |          |
| **Business Acquisition [Line Items]**                                                                          |          |          |          |          |          |
| Cash and cash equivalents                                                                                      |          |          | $ 2,496       |          |          |
| Federal Funds sold                                                                                             |          |          | 7,018         |          |          |
| Interest-bearing time deposits                                                                                 |          |          | 922           |          |          |
| Loans                                                                                                          |          |          | 110,625       |          |          |
| Premises and equipment                                                                                         |          |          | 7,290         |          |          |
| Federal Home Loan Bank stock                                                                                   |          |          | 855           |          |          |
| Interest receivable                                                                                            |          |          | 292           |          |          |
| Other assets                                                                                                   |          |          | 119           |          |          |
| Deposits                                                                                                       |          |          | (105,326)     |          |          |
| Interest payable                                                                                               |          |          | (29)          |          |          |
| Federal Home Loan Bank Advances                                                                                |          |          | (18,958)      |          |          |
| Other liabilities                                                                                              |          |          | (2,911)       |          |          |
| Net tangible assets acquired                                                                                   |          |          | 2,393         |          |          |
| Core deposit intangible                                                                                        |          |          | 981           |          |          |
| Goodwill                                                                                                       |          |          | 11,126        |          |          |
| Purchase price                                                                                                 |          |          | $ 14,500      |          |          |

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.
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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.
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The amount of identifiable intangible assets recognized as of the acquisition date.
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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.
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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.
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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.
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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.
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The amount of property, plant, and equipment recognized as of the acquisition date.
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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.
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