Loans, Past Due And Accruing Restructured (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Financing receivables, non accruals, past due, and accruing restructured loans [Line Items]
Total non-accrual loans	$ 3,173,000		$ 2,283,000
Past-due 90 days or more and still accruing	180,000		128,000
Total non-accrual and past-due 90 days or more and still accruing	3,353,000		2,411,000
Accruing restructured Loans	13,693,000		13,343,000
Total	17,046,000		15,754,000
Percentage of total non-accrual and past-due 90 days or more and still accruing to total loans (in hundredths)	0.61%		0.53%
Percentage of total non-accrual, past-due 90 days or more and still accruing, and accruing restructured loans to total loans (in hundredths)	3.10%		3.47%
Loans sold to Federal Home Loan Mortgage Corporation Loans serviced for other investors unpaid balance	87,710,000		71,568,000
Total loans sold to Federal Home Loan Mortgage Corporation	7,175,000	5,866,000
Commercial and Industrial [Member]
Financing receivables, non accruals, past due, and accruing restructured loans [Line Items]
Total non-accrual loans	181,000		264,000
Commercial Secured By Real Estate [Member]
Financing receivables, non accruals, past due, and accruing restructured loans [Line Items]
Total non-accrual loans	1,414,000		788,000
Residential Real Estate [Member]
Financing receivables, non accruals, past due, and accruing restructured loans [Line Items]
Total non-accrual loans	$ 1,578,000		$ 1,231,000