Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	$ 13,187	$ 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	5,708	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	1,995	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	7,703	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	473	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	3,946	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	995	1,868
Total accruing loans which are contractually past due 90 days or more	6	1,077
Consumer
Schedule of Financing Receivables Nonaccrual [Line Items]
Total non-accrual loans	70	0
Total accruing loans which are contractually past due 90 days or more	$ 45	$ 6