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, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 652,186	$ 698,457
Carrying Amount	614,843	658,471
Allowance	480	650
Carrying Amount Net of Allowance	614,363	657,821
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	70,753	79,124
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	1,614	1,993
Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	27,303	28,176
Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	316,523	341,195
Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	172,373	180,643
Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	61,606	64,883
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	1,930	2,357
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	84	86
Merger with Community Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	135,383	142,989
Carrying Amount	126,996	134,198
Allowance	195
Carrying Amount Net of Allowance	126,801	134,198
Merger with Community Bancshares, Inc. \| Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	6,828	8,168
Merger with Community Bancshares, Inc. \| Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	737	1,100
Merger with Community Bancshares, Inc. \| Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	19,969	19,063
Merger with Community Bancshares, Inc. \| Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	69,421	74,600
Merger with Community Bancshares, Inc. \| Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	28,048	28,863
Merger with Community Bancshares, Inc. \| Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	9,324	9,881
Merger with Community Bancshares, Inc. \| Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	1,056	1,314
Merger with Community Bancshares, Inc. \| Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired
Merger with CFS Bancorp, Inc. (Citizens)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	473,781	509,660
Carrying Amount	450,867	484,949
Allowance	285	650
Carrying Amount Net of Allowance	450,582	484,299
Merger with CFS Bancorp, Inc. (Citizens) \| Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	58,252	64,897
Merger with CFS Bancorp, Inc. (Citizens) \| Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	7,334	9,113
Merger with CFS Bancorp, Inc. (Citizens) \| Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	232,436	251,002
Merger with CFS Bancorp, Inc. (Citizens) \| Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	137,457	144,396
Merger with CFS Bancorp, Inc. (Citizens) \| Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	37,439	39,244
Merger with CFS Bancorp, Inc. (Citizens) \| Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	779	922
Merger with CFS Bancorp, Inc. (Citizens) \| Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	84	86
SCB Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	43,022	45,808
Carrying Amount	36,980	39,324
Allowance
Carrying Amount Net of Allowance	36,980	39,324
SCB Bank \| Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	5,673	6,059
SCB Bank \| Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	877	893
SCB Bank \| Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	14,666	15,593
SCB Bank \| Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	6,868	7,384
SCB Bank \| Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	14,843	15,758
SCB Bank \| Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	95	121
SCB Bank \| Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount Gross

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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=d3e13503-111538

Reference 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=d3e13503-111538

Reference 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

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