| **Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Details) - USD ($) $ in Thousands** | Sep. 30, 2015 | Dec. 31, 2014 |
|---------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | $ 32,597      | $ 48,789      |
| Commercial and industrial loans                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 4,460         | 7,048         |
| Agricultural production financing and other loans to farmers                                            |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 1,210         | 5,800         |
| Real estate loans - Construction                                                                        |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 745           | 1,439         |
| Real estate loans - Commercial and farmland                                                             |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 13,506        | 19,350        |
| Real estate loans - Residential                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 10,749        | 12,933        |
| Real estate loans - Home Equity                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | 1,783         | 1,988         |
| Individuals' loans for household and other personal expenditures                                        |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                        |          |          |
| Non-accrual loans                                                                                       | $ 144         | $ 231         |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5111-111524
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| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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