| **Loans and Allowance - Composition of Impaired Loans by Loan Class (Details) (USD $)In Thousands, unless otherwise specified** | 3 Months Ended | 9 Months Ended |              |
|---------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|--------------|
||
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | $ 83,225       |           | $ 83,225     |   | $ 109,594 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                | 7,713          |           | 7,713        |   | 12,918 |
| Unpaid Principal Balance                                                                                                        | 90,938         |           | 90,938       |   | 122,512 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 47,603         |           | 47,603       |   | 67,333 |
| Impaired loans with related allowance - Recorded Investment                                                                     | 6,624          |           | 6,624        |   | 11,846 |
| Recorded Investment                                                                                                             | 54,227         |           | 54,227       |   | 79,179 |
| Impaired loans with related allowance - Related Allowance                                                                       | 1,475          |           | 1,475        |   | 4,243 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 49,875         | 55,699         | 52,494       | 61,126 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             | 6,681          | 19,565         | 6,811        | 19,704 |   |
| Average Recorded Investment                                                                                                     | 56,556         | 75,264         | 59,305       | 80,830 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           | 841            | 316            | 2,026        | 886 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              | 5              | 62             | 12           | 183 |   |
| Interest Income Recognized                                                                                                      | 846            | 378            | 2,038        | 1,069 |   |
| Commercial and industrial loans                                                                                                 |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 21,683         |           | 21,683       |   | 28,532 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                | 1,119          |           | 1,119        |   | 4,415 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 7,758          |           | 7,758        |   | 11,730 |
| Impaired loans with related allowance - Recorded Investment                                                                     | 853            |           | 853          |   | 4,155 |
| Impaired loans with related allowance - Related Allowance                                                                       | 401            |           | 401          |   | 1,628 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 8,352          | 9,994          | 9,553        | 11,615 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             | 865            | 5,244          | 889          | 5,307 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           | 110            | 26             | 184          | 68 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              |      | 11             | 7            | 32 |   |
| Agriculture production financing and other loans to farmers                                                                     |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 33             |           | 33           |   |   |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 31             |           | 31           |   |   |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 32             | 300            | 33           | 300 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           |           |      |         |    |   |
| Real estate loans - Construction                                                                                                |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 6,161          |           | 6,161        |   | 9,787 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                |      |           |    |   | 1,202 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 3,789          |           | 3,789        |   | 5,164 |
| Impaired loans with related allowance - Recorded Investment                                                                     |      |           |    |   | 1,058 |
| Impaired loans with related allowance - Related Allowance                                                                       |      |           |    |   | 105 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 4,115          | 6,658          | 4,262        | 7,665 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             |      | 510            |    | 541 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           | 29             | 17             | 85           | 47 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              |           |      |         |    |   |
| Real estate loans - Commercial and farm land                                                                                    |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 46,834         |           | 46,834       |   | 58,173 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                | 6,520          |           | 6,520        |   | 5,579 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 33,085         |           | 33,085       |   | 43,204 |
| Impaired loans with related allowance - Recorded Investment                                                                     | 5,700          |           | 5,700        |   | 5,182 |
| Impaired loans with related allowance - Related Allowance                                                                       | 1,068          |           | 1,068        |   | 2,460 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 34,298         | 31,081         | 35,198       | 33,459 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             | 5,742          | 12,326         | 5,844        | 12,371 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           | 620            | 250            | 1,642        | 706 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              | 5              | 32             | 5            | 95 |   |
| Real estate loans - Residential                                                                                                 |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 4,671          |           | 4,671        |   | 8,820 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                | 74             |           | 74           |   | 1,722 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 2,569          |           | 2,569        |   | 6,215 |
| Impaired loans with related allowance - Recorded Investment                                                                     | 71             |           | 71           |   | 1,451 |
| Impaired loans with related allowance - Related Allowance                                                                       | 6              |           | 6            |   | 50 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 2,687          | 6,936          | 3,028        | 7,342 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             | 74             | 1,485          | 78           | 1,485 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           | 82             | 20             | 114          | 54 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              |      | 19             |    | 56 |   |
| Real estate loans - Home equity                                                                                                 |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 3,386          |           | 3,386        |   | 4,199 |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 199            |           | 199          |   | 1,006 |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 217            | 713            | 236          | 727 |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           |      | 3              |    | 10 |   |
| Other Loans                                                                                                                     |           |           |         |   |   |
| **Financing Receivable, Impaired [Line Items]**                                                                                 |           |           |         |   |   |
| Impaired loans with no related allowance - Unpaid Principal Balance                                                             | 457            |           | 457          |   | 83 |
| Impaired loans with related allowance - Unpaid Principal Balance                                                                |      |           |    |   |   |
| Impaired loans with no related allowance - Recorded Investment                                                                  | 172            |           | 172          |   | 14 |
| Impaired loans with related allowance - Recorded Investment                                                                     |      |           |    |   |   |
| Impaired loans with related allowance - Related Allowance                                                                       |      |           |    |   |   |
| Impaired loans with no related allowance - Average Recorded Investment                                                          | 174            | 17             | 184          | 18 |   |
| Impaired loans with related allowance - Average Recorded Investment                                                             |      |           |    |   |   |
| Impaired loans with no related allowance - Interest Income Recognized                                                           |           |      |         | 1 |   |
| Impaired loans with related allowance - Interest Income Recognized                                                              |      |           |    |   |   |

| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivableImpairedLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of allowance for credit losses related to recorded investment.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableRelatedAllowance**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |