Goodwill and other Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Roll Forward]
Beginning Balance	$ 132,029,000	$ 114,841,000
Goodwill acquired	20,344,000	17,188,000
Ending Balance	152,373,000	132,029,000	114,841,000
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	34,983,000	32,885,000
Less: accumulated amortization	18,021,000	14,691,000
Net carrying amount	16,962,000	18,194,000
Amortization Expense
Amortization of intangible assets	3,394,000	3,046,000	3,072,000
Future Amortization Expense
2013	3,300,000
2014	3,100,000
2015	2,900,000
2016	1,800,000
2017	1,400,000
Thereafter	2,400,000
Indefinite-lived intangible assets (Excluding goodwill)	2,000,000
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (in years)	1
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (in years)	12
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	13,240,000	11,966,000
Less: accumulated amortization	7,794,000	6,401,000
Net carrying amount	5,446,000	5,565,000
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	21,743,000	20,919,000
Less: accumulated amortization	10,227,000	8,290,000
Net carrying amount	$ 11,516,000	$ 12,629,000