Premises and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 164,863,000	$ 150,708,000
Less accumulated depreciation and amortization	(46,155,000)	(42,809,000)
Total	118,708,000	107,899,000
Depreciation and amortization expense	6,300,000	5,700,000	5,200,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	39,441,000	34,240,000
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	84,407,000	78,165,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,684,000	2,735,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	24,110,000	23,097,000
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	438,000	428,000
Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 13,783,000	$ 12,043,000