Loans and Allowance for Loan Losses, Troubled Debt Restructurings (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	8	4
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 7,591,000	$ 1,604,000
Number of TDR loans secured by business assets	9
TDR loans value	6,634,000
Number of TDR loans current and performing	6
TDR loans current and performing	5,557,000
Number of borrowers with performing loans	4
Number of borrowers with nonperforming loans	2
Number of TDR loans not performing in accordance with the modified terms	3
TDR loans not performing in accordance with modified terms	1,077,000
Non-performing Assets, Restructured Loans Still Accruing and Loans Contractually Past Due [Abstract]
Non-accrual loans	10,650,000	4,621,000	2,109,000
Other real estate owned	1,406,000	1,776,000	2,821,000
Other repossessed assets owned	0	15,000	21,000
Non-performing corporate bond investments, at fair value	325,000	335,000	552,000
Total non-performing assets	12,381,000	6,747,000	5,503,000
Restructured loans still accruing	5,556,000	0	0
Loans past due 90 or more days and still accruing	132,000	101,000	263,000
Total non-performing and other risk assets	18,069,000	6,848,000	5,766,000
Allowance for loan losses to total loans (in hundredths)	1.39%	1.47%	1.35%
Non-accrual loans to total loans (in hundredths)	2.36%	1.01%	0.45%
Allowance for loan losses to non-accrual loans (in hundredths)	58.76%	145.01%	299.10%
Total non-accrual loans and restructured loans still accruing to total loans (in hundredths)	3.59%	1.01%	0.45%
Allowance for loan losses to non-accrual loans and restructured loans still accruing (in hundredths)	38.62%	145.61%	299.10%
Total non-performing assets to total assets (in hundredths)	2.06%	1.10%	0.92%
Number of restructured loans on non accrual status included with non accrual loans	3	4
Restructured loans on non accrual status	1,077,000	1,604,000
Number of days in delay in required loan repayment considered insignificant, maximum	30 days
Percentage of shortfall in required loan repayment considered insignificant, maximum (in hundredths)	5.00%
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	2	2
Troubled debt restructurings, pre-modification outstanding recorded investment	435,000	436,000
Troubled debt restructurings, post-modification outstanding recorded investment	435,000	436,000
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	2	0
Troubled debt restructurings, pre-modification outstanding recorded investment	3,683,000	0
Troubled debt restructurings, post-modification outstanding recorded investment	3,683,000	0
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Construction and Land [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	4	0
Troubled debt restructurings, pre-modification outstanding recorded investment	3,473,000	0
Troubled debt restructurings, post-modification outstanding recorded investment	3,473,000	0
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	0	0
Troubled debt restructurings, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings, post-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	0	2
Troubled debt restructurings, pre-modification outstanding recorded investment	0	1,168,000
Troubled debt restructurings, post-modification outstanding recorded investment	0	1,168,000
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Home Equity Line of Credit [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	0	0
Troubled debt restructurings, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings, post-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, number of contracts	0	0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	0	0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	0	0
Commercial Real Estates [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts		1
Troubled debt restructurings, pre-modification outstanding recorded investment		$ 1,900,000