| **Business Combinations (Details) (USD $)In Millions, except Per Share data, unless otherwise specified** | Sep. 30, 2013 | Dec. 31, 2012 | May 13, 2013Merger with CFS Bancorp, Inc. (Citizens) | May 13, 2013Merger with CFS Bancorp, Inc. (Citizens)Citizens | Oct. 31, 2013Subsequent eventMerger with CFS Bancorp, Inc. (Citizens) |
|-----------------------------------------------------------------------------------------------------------|---------------|---------------|------------------------------------------------------|--------------------------------------------------------------|-----------------------------------------------------------------------|
| **Business Acquisition [Line Items]**                                                                     |          |          |                                                 |                                                         |                                                                  |
| Share price (in dollars per share)                                                                        |          |          |                                                 |                                                         | $ 18.80                                                               |
| Estimated transaction value                                                                               |          |          |                                                 |                                                         | $ 134                                                                 |
| Common stock, par or stated value (in dollars per share)                                                  | $ 0.125       | $ 0.125       | $ 0.125                                              | $ 0.01                                                       |                                                                  |
| Share exchange ratio                                                                                      |          |          | 0.65                                                 |                                                         |                                                                  |

| X                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Combination, Share Exchange Ratio
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Face amount or stated value per share of common stock.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Price of a single share of a number of saleable stocks of a company.
+ References
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