Credit Quality of Loans and Allowance for Loan Losses, Aggregate Allowance for Loan Losses and Related Party Lending (Details) (USD $)	6 Months Ended
	Jun. 30, 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	$ 167,100,000
Exposure in oil and gas industry specified as percentage of total loans (in hundredths)	14.90%
Loans with exposure in commercial real estate	468,700,000
Loans on nonaccrual status	6,772,000	8,887,000
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans with exposure in commercial real estate	351,400,000
Percentage of CRE loans secured by owner-occupied commercial properties (in hundredths)	59.30%
Loans on nonaccrual status	$ 2,900,000
Nonaccrual status of loans specified as percentage of total CRE loans (in hundredths)	0.60%