Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	$ 5,053	$ 11,685
Total accruing loans which are contractually past due 90 days or more	68	54
Commercial Real Estate Owner Occupied
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	2,742	5,564
Commercial Real Estate Non Owner Occupied
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	434	1,940
Commercial real estate
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	3,176	7,504
Construction
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	0	216
Residential real estate
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	1,427	3,165
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	447	744
Total accruing loans which are contractually past due 90 days or more	56	9
Consumer
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	3	56
Total accruing loans which are contractually past due 90 days or more	$ 12	$ 45