Loans and Allowance for Loan Losses, Troubled Debt Restructurings (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 Borrower Contract Loan	Dec. 31, 2012	Mar. 31, 2012	Mar. 31, 2011
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings, number of contracts	2
Troubled debt restructurings, pre-modification outstanding recorded investment	$ 2,000,000
Number of TDR loans secured by business assets	10
TDR loans value	8,400,000
Number of TDR loans current and performing	7
TDR loans current and performing	7,400,000
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	1,000,000
Non-performing Assets, Restructured Loans Still Accruing and Loans Contractually Past Due [Abstract]
Non-accrual loans	10,368,000	10,650,000	10,650,000	4,846,000
Other real estate owned	1,406,000		1,406,000	1,776,000
Non-performing corporate bond investments, at fair value	79,000		325,000	276,000
Total non-performing assets	11,853,000		12,381,000	6,898,000
Restructured loans still accruing	7,384,000		5,556,000	0
Loans past due 90 or more days and still accruing	0	132,000	132,000	86,000
Total non-performing and other risk assets	19,237,000		18,069,000	6,984,000
Allowance for loan losses to total loans (in hundredths)	1.35%		1.39%	1.50%
Non-accrual loans to total loans (in hundredths)	2.31%		2.36%	1.06%
Allowance for loan losses to non-accrual loans (in hundredths)	58.72%		58.76%	141.91%
Total non-accrual loans and restructured loans still accruing to total loans (in hundredths)	3.95%		3.59%	1.06%
Allowance for loan losses to non-accrual loans and restructured loans still accruing (in hundredths)	34.29%		38.62%	141.91%
Total non-performing assets to total assets (in hundredths)	1.99%		2.06%	1.16%
Commercial and Industrial [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	1		0
Troubled debt restructurings that subsequently defaulted, pre-modification outstanding recorded investment	237,000		0
Troubled debt restructurings that subsequently defaulted, post-modification outstanding recorded investment	237,000		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	2,010,000		0
Troubled debt restructurings, post-modification outstanding recorded investment	2,010,000		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	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
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		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
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