Loans and allowance for credit losses (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Loans individually evaluated for impairment	$ 85,096	$ 88,827
Loans collectively evaluated for impairment	697,092	696,255
Total loans	782,188	785,082
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	3,312	2,201
Loans collectively evaluated for impairment	12,411	13,790
Total allowance for credit losses	15,723	15,991
Unallocated Financing Receivables [Member]
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	0	0
Total loans	0	0
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	87	187
Total allowance for credit losses	87	187
Commercial Loan [Member]
Loans individually evaluated for impairment	711	715
Loans collectively evaluated for impairment	55,737	60,071
Total loans	56,448	60,786
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	29	0
Loans collectively evaluated for impairment	1,187	1,682
Total allowance for credit losses	1,216	1,682
Consumer Loan [Member]
Loans individually evaluated for impairment	51	87
Loans collectively evaluated for impairment	11,488	13,206
Total loans	11,539	13,293
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	0	48
Loans collectively evaluated for impairment	301	359
Total allowance for credit losses	301	407
Residential Real Estate [Member]
Loans individually evaluated for impairment	22,438	18,549
Loans collectively evaluated for impairment	266,056	269,462
Total loans	288,494	288,011
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	377	598
Loans collectively evaluated for impairment	3,882	4,596
Total allowance for credit losses	4,259	5,194
Commercial Real Estate [Member]
Loans individually evaluated for impairment	27,258	32,447
Loans collectively evaluated for impairment	293,933	282,494
Total loans	321,191	314,941
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	2,189	614
Loans collectively evaluated for impairment	3,325	3,520
Total allowance for credit losses	5,514	4,134
Construction Loans [Member]
Loans individually evaluated for impairment	34,638	37,029
Loans collectively evaluated for impairment	69,878	71,022
Total loans	104,516	108,051
Allowance for credit losses allocated to:
Loans individually evaluated for impairment	717	941
Loans collectively evaluated for impairment	3,629	3,446
Total allowance for credit losses	$ 4,346	$ 4,387