Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	$ 5,821	$ 7,226
Total accruing loans which are contractually past due 90 days or more	90	1,083
Commercial Real Estate Owner Occupied
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	2,572	4,443
Total accruing loans which are contractually past due 90 days or more	0	0
Commercial Real Estate Non Owner Occupied
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	280	280
Total accruing loans which are contractually past due 90 days or more	0	0
Commercial Real Estate
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	2,852	4,723
Total accruing loans which are contractually past due 90 days or more	0	0
Construction
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	106	236
Total accruing loans which are contractually past due 90 days or more	39	0
Residential real estate
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	465	399
Total accruing loans which are contractually past due 90 days or more	0	0
Commercial and Industrial
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	2,398	1,868
Total accruing loans which are contractually past due 90 days or more	0	1,077
Consumer
Schedule of Financing Receivables Nonaccrual [Line Items]
Total accruing loans which are contractually past due 90 days or more	$ 51	$ 6