Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans $ 11,685 $ 7,226
Total accruing loans which are contractually past due 90 days or more 54 1,083
Commercial Real Estate Owner Occupied    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 5,564 4,443
Commercial Real Estate Non Owner Occupied    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 1,940 280
Total accruing loans which are contractually past due 90 days or more 0 0
Commercial real estate    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 7,504 4,723
Total accruing loans which are contractually past due 90 days or more 0 0
Construction    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 216 236
Residential real estate    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 3,165 399
Total accruing loans which are contractually past due 90 days or more 0 0
Commercial and industrial    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 744 1,868
Total accruing loans which are contractually past due 90 days or more 9 1,077
Consumer    
Financing Receivable, Impaired [Line Items]    
Total non-accrual loans 56 0
Total accruing loans which are contractually past due 90 days or more $ 45 $ 6