Premises and Equipment (Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 76,092	$ 74,013
Accumulated depreciation and amortization	(34,201)	(31,140)
Premises and equipment, net	41,891	42,873
Gain (Loss) on Disposition of Property Plant Equipment	0	(11)	$ 0
Land and land improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,985	3,012
Buildings and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	37,054	36,958
Furniture, fixtures and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	36,053	34,043
Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	(3,500)	(3,200)
Capitalized Computer Software, Gross	3,800	3,600
Capital lease obligation
Property, Plant and Equipment [Line Items]
Capital Leased Assets, Gross	$ 855	$ 855
SBM Financial, Inc. [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Disposals			$ 1,100