Investment Securities, Amortized Cost, Maturities and Approximate Fair Value (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Amortized Cost [Abstract]
Due in one year or less	$ 68,312,000
Due from one to five years	111,534,000
Due from five to ten years	178,693,000
Due after ten years	27,242,000
Total securities available for sale	385,781,000
Fair Value [Abstract]
Due in one year or less	69,887,000
Due from one to five years	118,665,000
Due from five to ten years	186,461,000
Due after ten years	27,340,000
Total securities available for sale	402,353,000	299,204,000
Amortized Cost [Abstract]
Due in one year or less	1,544,000
Due from one to five years	6,013,000
Due from five to ten years	478,000
Total securities held to maturity	8,035,000
Total investment securities	393,816,000
Fair Value [Abstract]
Due in one year or less	1,556,000
Due from one to five years	6,771,000
Due from five to ten years	534,000
Total securities held to maturity	8,861,000
Total investment securities	411,214,000
Federal Reserve Bank Stock	1,000,000
Number of shares owned (in shares)	15,851
Federal Home Loan Bank Stock	2,000,000
Investment securities pledged	$ 286,000,000	$ 286,000,000