Loans and reserve for credit losses (Schedule of Accounts, Notes, Loans and Financing Receivable) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Commercial real estate:
Owner occupied	$ 195,111	$ 204,998
Non-owner occupied	348,597	347,014
Total commercial real estate loans	543,708	552,012
Construction	55,436	52,503
Residential real estate	100,550	101,557
Commercial and industrial	273,444	254,170
Consumer	34,216	35,990
Total loans, Amount	1,007,354	996,232
Less:
Deferred loan fees	(1,707)	(1,757)
Reserve for loan losses	(21,722)	(20,857)
Loans, net, Amount	$ 983,925	$ 973,618
Owner occupied, Percent	19.40%	20.60%
Non-owner occupied, Percent	34.60%	34.80%
Total commercial real estate loans, Percent	54.00%	55.40%
Construction, Percent	5.50%	5.30%
Residential real estate, Percent	10.00%	10.20%
Commercial and industrial, Percent	27.10%	25.50%
Consumer, Percent	3.40%	3.60%
Total loans, Percent	100.00%	100.00%