| **Accounting for Certain Loans Acquired in a Purchase  - Carrying Amount of Loans Included in Balance Sheet (Details) (USD $)In Thousands, unless otherwise specified** | Mar. 31, 2014 | Dec. 31, 2013 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | $ 660,617     | $ 690,218     |
| Carrying Amount                                                                                                                                                         | 616,739       | 636,182       |
| Allowance                                                                                                                                                               | 443           | 229           |
| Carrying Amount Net of Allowance                                                                                                                                        | 616,296       | 635,953       |
| Commercial and industrial loans                                                                                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 85,319        | 89,487        |
| Agricultural production financing and other loans to farmers                                                                                                            |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 941           | 1,161         |
| Real estate loans - Construction                                                                                                                                        |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 15,610        | 17,962        |
| Real estate loans - Commercial and farm land                                                                                                                            |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 321,415       | 335,049       |
| Real estate loans - Residential                                                                                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 170,951       | 176,113       |
| Real estate loans - Home equity                                                                                                                                         |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 64,122        | 67,278        |
| Individuals' loans for household and other personal expenditures                                                                                                        |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 2,169         | 2,629         |
| Other loans                                                                                                                                                             |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 90            | 539           |
| Merger with CFS Bancorp, Inc. (Citizens)                                                                                                                                |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 605,105       | 629,184       |
| Carrying Amount                                                                                                                                                         | 570,092       | 585,913       |
| Allowance                                                                                                                                                               | 426           |          |
| Carrying Amount Net of Allowance                                                                                                                                        | 569,666       | 585,913       |
| Merger with CFS Bancorp, Inc. (Citizens) | Commercial and industrial loans                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 77,480        | 81,303        |
| Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Construction                                                                                             |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 15,610        | 17,962        |
| Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Commercial and farm land                                                                                 |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 301,268       | 311,631       |
| Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Residential                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 162,265       | 166,754       |
| Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Home equity                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 46,428        | 49,042        |
| Merger with CFS Bancorp, Inc. (Citizens) | Individuals' loans for household and other personal expenditures                                                             |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 1,964         | 2,360         |
| Merger with CFS Bancorp, Inc. (Citizens) | Other loans                                                                                                                  |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 90            | 132           |
| SCB Bank                                                                                                                                                                |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 55,512        | 61,034        |
| Carrying Amount                                                                                                                                                         | 46,647        | 50,269        |
| Allowance                                                                                                                                                               | 17            | 229           |
| Carrying Amount Net of Allowance                                                                                                                                        | 46,630        | 50,040        |
| SCB Bank | Commercial and industrial loans                                                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 7,839         | 8,184         |
| SCB Bank | Agricultural production financing and other loans to farmers                                                                                                 |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 941           | 1,161         |
| SCB Bank | Real estate loans - Commercial and farm land                                                                                                                 |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 20,147        | 23,418        |
| SCB Bank | Real estate loans - Residential                                                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 8,686         | 9,359         |
| SCB Bank | Real estate loans - Home equity                                                                                                                              |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 17,694        | 18,236        |
| SCB Bank | Individuals' loans for household and other personal expenditures                                                                                             |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          | 205           | 269           |
| SCB Bank | Other loans                                                                                                                                                  |          |          |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                                                                                                        |          |          |
| Loans Acquired                                                                                                                                                          |     | $ 407         |

| X                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount Gross
+ References
No definition available.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor.  This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected.  This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses).  This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544
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