Goodwill, Core Deposit Premium and Other Intangible Assets (Book value, fair value of commercial serving rights and impairment) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Impairment		$ 0
Less than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	$ 1,136,000	1,237,000
Fair Value	1,147,000	1,297,000
Impairment	8,000	0
Less than 20 Years | Centennial Bank and Trust
Finite-Lived Intangible Assets [Line Items]
Book Value	28,000	0
Fair Value	30,000	0
Impairment	0	0
Less than 20 Years | Premier Valley Bank
Finite-Lived Intangible Assets [Line Items]
Book Value	191,000	189,000
Fair Value	208,000	200,000
Impairment	0	0
Less than 20 Years | Wisconsin Bank & Trust
Finite-Lived Intangible Assets [Line Items]
Book Value	917,000	1,048,000
Fair Value	909,000	1,097,000
Impairment	8,000	0
More than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	3,277,000	3,374,000
Fair Value	3,644,000	3,605,000
Impairment	38,000	0
More than 20 Years | Centennial Bank and Trust
Finite-Lived Intangible Assets [Line Items]
Book Value	140,000	0
Fair Value	148,000	0
Impairment	0	0
More than 20 Years | Premier Valley Bank
Finite-Lived Intangible Assets [Line Items]
Book Value	387,000	417,000
Fair Value	349,000	432,000
Impairment	38,000	0
More than 20 Years | Wisconsin Bank & Trust
Finite-Lived Intangible Assets [Line Items]
Book Value	2,750,000	2,957,000
Fair Value	3,147,000	3,173,000
Impairment	$ 0	$ 0