Premises and Equipment, Net (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	$ 160,922,000	$ 151,120,000
Accumulated depreciation	83,047,000	76,579,000
Total premises and equipment	77,875,000	74,541,000
Rental expense	6,400,000	5,600,000	5,300,000
Operating Leases, Future Minimum Payments Due [Abstract]
2013	5,727,000
2014	5,453,000
2015	4,714,000
2016	4,309,000
2017	4,063,000
Thereafter	28,314,000
Total	52,580,000
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	109,601,000	103,399,000
Pledged to secure long-term borrowings	2,700,000	2,900,000
Equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	51,321,000	47,646,000
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)	3
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)	10
Construction In Progress [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	$ 0	$ 75,000
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)	15
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)	40