Accounting for Certain Loans Acquired in a Purchase - Carrying Amount of Loans Included in Balance Sheet (Details) $ in Thousands	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	$ 790,300	$ 698,097
Carrying Amount	762,893	665,417
Allowance	504	380
Loans acquired and accounted for under ASC 310-30, carrying amount	762,389	665,037
Loans Acquired with Deteriorated Credit Quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	36,700	60,500
Loans acquired and accounted for under ASC 310-30, carrying amount	27,200	43,200
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	22,597	37,236
Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,262	2,710
Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	39,145	29,298
Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	329,560	303,362
Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	324,357	257,640
Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	69,618	64,819
Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,891	1,142
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,870	1,890
Transferred to Other Real Estate Owned | Loans Acquired with Deteriorated Credit Quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance		12,100
Loans acquired and accounted for under ASC 310-30, carrying amount		$ 7,600
Loans transferred to Other Real Estate Owned, number | loan		1
Arlington Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	220,537
Carrying Amount	213,976
Allowance
Loans acquired and accounted for under ASC 310-30, carrying amount	213,976
Arlington Bank | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	2,853
Arlington Bank | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance
Arlington Bank | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	21,990
Arlington Bank | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	87,050
Arlington Bank | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	94,047
Arlington Bank | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	13,542
Arlington Bank | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,055
Arlington Bank | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance
Ameriana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	219,765	$ 250,824
Carrying Amount	212,297	240,053
Allowance	412	265
Loans acquired and accounted for under ASC 310-30, carrying amount	211,885	239,788
Ameriana | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	6,424	8,003
Ameriana | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance
Ameriana | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	13,817	22,017
Ameriana | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	92,872	103,075
Ameriana | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	94,257	103,414
Ameriana | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	10,042	11,728
Ameriana | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	545	762
Ameriana | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,808	1,825
C Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	66,088	77,100
Carrying Amount	64,449	75,194
Loans acquired and accounted for under ASC 310-30, carrying amount	64,449	75,194
C Financial | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	75	85
C Financial | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,448	2,835
C Financial | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	19,034	22,130
C Financial | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	38,575	44,101
C Financial | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	6,956	7,947
C Financial | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance		2
Community
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	46,136	60,108
Carrying Amount	43,514	56,007
Allowance	53	23
Loans acquired and accounted for under ASC 310-30, carrying amount	43,461	55,984
Community | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	459	2,269
Community | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	98	1,030
Community | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,770	4,026
Community | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	31,091	36,947
Community | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	7,664	9,363
Community | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	4,951	6,326
Community | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	103	147
CFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	212,227	279,479
Carrying Amount	205,695	266,845
Allowance	39	92
Loans acquired and accounted for under ASC 310-30, carrying amount	205,656	266,753
CFS | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	10,595	23,327
CFS | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	50	50
CFS | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	120	420
CFS | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	91,676	131,895
CFS | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	86,632	96,627
CFS | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	22,929	26,894
CFS | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	163	201
CFS | Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	62	65
SCB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	25,547	30,586
Carrying Amount	22,962	27,318
Loans acquired and accounted for under ASC 310-30, carrying amount	22,962	27,318
SCB | Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	2,191	3,552
SCB | Agricultural production financing and other loans to farmers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	1,114	1,630
SCB | Real estate loans - Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance
SCB | Commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	7,837	9,315
SCB | Real estate loans - Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	3,182	4,135
SCB | Real estate loans - Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	11,198	11,924
SCB | Individuals' loans for household and other personal expenditures
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired and accounted for under ASC 310-30, outstanding balance	$ 25	$ 30