Loans (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012 item	Dec. 31, 2012
Troubled debt restructurings
Loans classified as TDRs	$ 10,000,000		$ 11,600,000
Accruing loans that were classified as TDRs	1,300,000		17,000
Interest loss related to rate concessions on certain TDRs	45,000	22,000
Number of TDRs	3	1
Pre-Modification Outstanding Recorded Investment	91,000	65,000
Post-Modification Outstanding Recorded Investment	91,000	65,000
Troubled Debt Restructurings That Subsequently Defaulted
Number of TDRs	1	1
Recorded Investment	49,000	172,000
Minimum
Troubled debt restructurings
Period of maturity date extensions granted	12 months
Maximum
Troubled debt restructurings
Period of maturity date extensions granted	18 months
Commercial | Commercial and industrial
Troubled debt restructurings
Number of TDRs	3	1
Pre-Modification Outstanding Recorded Investment	91,000	65,000
Post-Modification Outstanding Recorded Investment	91,000	65,000
Troubled Debt Restructurings That Subsequently Defaulted
Number of TDRs	1	1
Recorded Investment	$ 49,000	$ 172,000