| **Loans and Allowance - Summary of Non-Accrual Loans by Loan Class (Details) (USD $)In Thousands, unless otherwise specified** | Jun. 30, 2013 | Dec. 31, 2012 |
|--------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | $ 38,971      | $ 53,399      |
| Commercial and industrial loans                                                                                                |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 8,543         | 12,195        |
| Agriculture production financing and other loans to farmers                                                                    |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 33            |     |
| Real estate loans - Construction                                                                                               |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 2,492         | 4,814         |
| Real estate loans - Commercial and farm land                                                                                   |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 15,352        | 22,612        |
| Real estate loans - Residential                                                                                                |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 11,148        | 11,476        |
| Real estate loans - Home equity                                                                                                |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | 1,234         | 1,997         |
| Lease financing receivables, net of unearned income                                                                            |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              |     | 301           |
| Other Loans                                                                                                                    |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                               |          |          |
| Non-accrual loans                                                                                                              | $ 169         | $ 4           |

| X                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AccountsNotesAndLoansReceivableLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| 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=7512638&loc=d3e5111-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |