Accounting for Certain Loans Acquired in a Purchase - Carrying Amount of Loans Included in Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 724,542	$ 698,457
Carrying Amount	687,096	658,471
Allowance	353	650
Carrying Amount Net of Allowance	686,743	657,821
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	71,797	79,124
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	2,818	1,993
Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	26,479	28,176
Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	330,997	341,195
Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	222,140	180,643
Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	68,780	64,883
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	1,448	2,357
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	83	86
Merger with C Financial Corporation
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	107,277
Carrying Amount	$ 104,714
Allowance
Carrying Amount Net of Allowance	$ 104,714
Merger with C Financial Corporation | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 114
Merger with C Financial Corporation | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired
Merger with C Financial Corporation | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 7,267
Merger with C Financial Corporation | Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	28,287
Merger with C Financial Corporation | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	61,188
Merger with C Financial Corporation | Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	10,407
Merger with C Financial Corporation | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 14
Merger with C Financial Corporation | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired
Merger with Community Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 119,692	142,989
Carrying Amount	112,171	$ 134,198
Allowance	193
Carrying Amount Net of Allowance	111,978	$ 134,198
Merger with Community Bancshares, Inc. | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	7,245	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	1,534	1,100
Merger with Community Bancshares, Inc. | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	12,600	19,063
Merger with Community Bancshares, Inc. | Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	63,460	74,600
Merger with Community Bancshares, Inc. | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	25,337	28,863
Merger with Community Bancshares, Inc. | Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	8,805	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	$ 711	$ 1,314
Merger with Community Bancshares, Inc. | Other commercial 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	$ 455,527	$ 509,660
Carrying Amount	433,744	484,949
Allowance	160	650
Carrying Amount Net of Allowance	433,584	484,299
Merger with CFS Bancorp, Inc. (Citizens) | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	59,166	64,897
Merger with CFS Bancorp, Inc. (Citizens) | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	50
Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	6,612	9,113
Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	224,675	251,002
Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	128,972	144,396
Merger with CFS Bancorp, Inc. (Citizens) | Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	35,327	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	642	922
Merger with CFS Bancorp, Inc. (Citizens) | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	83	86
SCB Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	42,046	45,808
Carrying Amount	$ 36,467	$ 39,324
Allowance
Carrying Amount Net of Allowance	$ 36,467	$ 39,324
SCB Bank | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	5,272	6,059
SCB Bank | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	1,234	893
SCB Bank | Real estate loans - Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	14,575	15,593
SCB Bank | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	6,643	7,384
SCB Bank | Real estate loans - Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	14,241	15,758
SCB Bank | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired	$ 81	$ 121
SCB Bank | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Acquired