Business Combinations Business Combinations (Details) - USD ($) $ in Thousands		3 Months Ended
	Feb. 14, 2015	Mar. 31, 2016	Mar. 31, 2015	Mar. 11, 2016	Feb. 13, 2015
Business Acquisition [Line Items]
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Acquired During Period, at Acquisition, at Fair Value				$ 35,416	$ 154,496
Gain on acquisition		$ 1,704	$ 42,930
Merger-related expenses		38	$ 2,997
North Milwaukee State Bank
Business Acquisition [Line Items]
Cash and cash equivalents				4,545
Overnight investments				2,274
Investment securities available for sale				9,425
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Acquired During Period, at Acquisition, at Fair Value				35,416
Other real estate owned				330
Intangible asset				240
Other assets				216
Total assets acquired				52,446
Deposits				59,206
Short-term borrowings				1,662
Other liabilities				74
Total liabilities assumed				60,942
Fair value of net assets (liabilities) assumed				(8,496)
Cash received from FDIC				$ 10,200
Gain on acquisition	$ 1,704
Merger-related expenses		38
Revenue generated		$ 123