Goodwill, Core Deposit Premium and Other Intangible Assets (Book value, fair value of commercial serving rights and impairment) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Less than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	$ 622,000	$ 1,008,000
Fair Value	827,000	1,200,000
Impairment	0	0
More than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	2,239,000	2,715,000
Fair Value	2,631,000	2,927,000
Impairment	4,000	33,000
Citywide Banks | Less than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	12,000	19,000
Fair Value	15,000	23,000
Impairment	0	0
Citywide Banks | More than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	54,000	107,000
Fair Value	61,000	114,000
Impairment	0	0
Premier Valley Bank | Less than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	95,000	156,000
Fair Value	124,000	180,000
Impairment	0	0
Premier Valley Bank | More than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	317,000	359,000
Fair Value	313,000	326,000
Impairment	4,000	33,000
Wisconsin Bank & Trust | Less than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	515,000	833,000
Fair Value	688,000	997,000
Impairment	0	0
Wisconsin Bank & Trust | More than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value	1,868,000	2,249,000
Fair Value	2,257,000	2,487,000
Impairment	$ 0	$ 0