Loans and allowance for credit losses (Details 6) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current	$ 696,855	$ 741,925
30-59 days past due	1,850	4,576
60-89 days past due	2,412	1,647
90 days or more past due	9	460
Total past due	4,271	6,683
Nonaccrual	17,501	36,474
Total loans	718,627	785,082
Percent of total loans, Current	97.00%	94.50%
Percent of total loans, 30-59 days past due	0.30%	0.60%
Percent of total loans, 60-89 days past due	0.30%	0.20%
Percent of total loans, 90 days or more past due	0.00%	0.10%
Percent of total loans, Total past due	0.60%	0.90%
Percent of total loans, Non accrual	2.40%	4.60%
Commercial Loan [Member]
Current	54,164	59,746
30-59 days past due	248	380
60-89 days past due	21	66
90 days or more past due	0	0
Total past due	269	446
Nonaccrual	668	594
Total loans	55,101	60,786
Consumer Loan [Member]
Current	11,099	13,125
30-59 days past due	48	57
60-89 days past due	45	19
90 days or more past due	9	5
Total past due	102	81
Nonaccrual	47	87
Total loans	11,248	13,293
Residential Real Estate [Member]
Current	272,819	272,311
30-59 days past due	1,554	3,116
60-89 days past due	375	762
90 days or more past due	0	290
Total past due	1,929	4,168
Nonaccrual	5,405	11,532
Total loans	280,153	288,011
Commercial Real Estate [Member]
Current	297,841	298,522
30-59 days past due	0	887
60-89 days past due	1,971	800
90 days or more past due	0	165
Total past due	1,971	1,852
Nonaccrual	3,342	14,567
Total loans	303,154	314,941
Construction Loans [Member]
Current	60,932	98,221
30-59 days past due	0	136
60-89 days past due	0	0
90 days or more past due	0	0
Total past due	0	136
Nonaccrual	8,039	9,694
Total loans	$ 68,971	$ 108,051