Loans and allowance for credit losses (Details 6) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current	$ 744,048	$ 741,925
30-59 days past due	2,585	4,576
60-89 days past due	734	1,647
90 days or more past due	3	460
Total past due	3,322	6,683
Nonaccrual	34,818	36,474
Total loans	782,188	785,082
Percent of total loans, Current	95.10%	94.50%
Percent of total loans, 30-59 days past due	0.30%	0.60%
Percent of total loans, 60-89 days past due	0.10%	0.20%
Percent of total loans, 90 days or more past due	0.00%	0.10%
Percent of total loans, Total past due	0.40%	0.90%
Percent of total loans, Non accrual	4.50%	4.60%
Commercial Loan [Member]
Current	55,720	59,746
30-59 days past due	112	380
60-89 days past due	14	66
90 days or more past due	0	0
Total past due	126	446
Nonaccrual	602	594
Total loans	56,448	60,786
Consumer Loan [Member]
Current	11,414	13,125
30-59 days past due	60	57
60-89 days past due	11	19
90 days or more past due	3	5
Total past due	74	81
Nonaccrual	51	87
Total loans	11,539	13,293
Residential Real Estate [Member]
Current	270,575	272,311
30-59 days past due	1,644	3,116
60-89 days past due	242	762
90 days or more past due	0	290
Total past due	1,886	4,168
Nonaccrual	16,033	11,532
Total loans	288,494	288,011
Commercial Real Estate [Member]
Current	309,318	298,522
30-59 days past due	769	887
60-89 days past due	467	800
90 days or more past due	0	165
Total past due	1,236	1,852
Nonaccrual	10,637	14,567
Total loans	321,191	314,941
Construction Loans [Member]
Current	97,021	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	7,495	9,694
Total loans	$ 104,516	$ 108,051