Acquisition Activities - (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 01, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Bargain purchase gain		$ 1,048
Amortization and accretion of purchase discounts and premiums		(4,124)	$ (5,010)	$ (8,285)
Amortization of acquired identifiable intangibles		5,400	5,300	$ 5,300
Pine River Bank Corporation [Member]
Business Acquisition [Line Items]
Cash	$ 9,482
Bargain purchase gain	1,048
Core deposit intangible asset	$ 948
Amortization period for core deposit intangible	7 years
Gross contractual amounts receivable	$ 79,000
Loans not expected to be collected	1,400
Recorded fair value	$ 64,300
Acquisition related expenses		700
Amortization and accretion of purchase discounts and premiums		153
Amortization of acquired identifiable intangibles		56
Pro forma information
Total revenue		195,500	187,400
Net income		$ 4,300	$ 8,900
Basic earnings per share (in dollars per share)		$ 0.13	$ 0.21
Diluted earnings per share (in dollars per share)		$ 0.13	$ 0.21