| **Business Combination (Tables) (Merger with CFS Bancorp, Inc. (Citizens))**                    | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| Merger with CFS Bancorp, Inc. (Citizens)                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| **Business Acquisition [Line Items]**                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Schedule of preliminary valuations of the fair value of assets acquired and liabilities assumed | Based on preliminary valuations of the fair value of tangible and intangible assets acquired and liabilities assumed, which are based on assumptions that are subject to change, the purchase price for the CFS acquisition was allocated as follows: Fair ValueCash and cash equivalents$10,992Interest-bearing time deposits213,379Investment securities available for sale15,913Investment securities held to maturity14,372Mortgage loans held for sale189Loans603,114Premises and equipment19,643Federal Home Loan Bank stock6,188Interest receivable1,770Cash surrender value of life insurance36,555Other real estate owned12,857Tax asset, deferred and receivable30,717Other assets111,656Deposits(955,432)Securities sold under repurchase agreements(9,830)Federal Home Loan Bank advances(15,000)Interest payable(294)Other liabilities(16,033)Net tangible assets acquired80,756Core deposit intangible7,313Goodwill47,573Purchase price$135,642 |
| Schedule of pro forma information from acquisition                                              | The following schedule includes pro forma results for the periods ended December 31, 2013 and 2012 as if the CFS acquisition had occurred as of the beginning of the periods presented.   2013 2012Total revenue (net interest income plus other income)$243,972 $266,034Net income$38,637 $50,092Net income available to common shareholders$36,257 $45,553Earnings per share:   Basic$0.98 $1.28Diluted$0.98 $1.27                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |

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| - Definition
Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2)-(3) -URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463
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| - Definition
Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472
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