Loans and reserve for credit losses (Details 7) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Total non-accrual loans	$ 10,903	$ 17,220
Total accruing loans which are contractually past due 90 days or more	258	1,533
Commercial Real Estate Owner Occupied [Member]
Total non-accrual loans	5,446	4,836
Total accruing loans which are contractually past due 90 days or more	26	0
Commercial Real Estate Non Owner Occupied [Member]
Total non-accrual loans	1,022	5,756
Total accruing loans which are contractually past due 90 days or more	0	1,427
Commerical real estate [Member]
Total non-accrual loans	6,468	10,592
Total accruing loans which are contractually past due 90 days or more	26	1,427
Construction [Member]
Total non-accrual loans	1,018	2,839
Total accruing loans which are contractually past due 90 days or more	134	0
Residential real estate [Member]
Total non-accrual loans	734	556
Total accruing loans which are contractually past due 90 days or more	0	94
Commercial and Industrial [Member]
Total non-accrual loans	2,683	3,233
Total accruing loans which are contractually past due 90 days or more	97	0
Consumer [Member]
Total accruing loans which are contractually past due 90 days or more	$ 1	$ 12