Credit Quality of Loans and Allowance for Loan Losses, Aggregate Allowance for Loan Losses and Related Party Lending (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 Segment	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of industry segment concentration above threshold limit	1
Threshold percentage of loan portfolio (in hundredths)	10.00%
Loans exposure in oil and gas industry	$ 144,100,000
Exposure in oil and gas industry specified as percentage of total loans (in hundredths)	13.90%
Loans with exposure in commercial real estate	470,800,000
Loans on nonaccrual status	7,526,000	8,887,000
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans with exposure in commercial real estate	348,500,000
Percentage of CRE loans secured by owner-occupied commercial properties (in hundredths)	58.20%
Loans on nonaccrual status	$ 3,600,000
Nonaccrual status of loans specified as percentage of total CRE loans (in hundredths)	0.80%