Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	$ 13,695	$ 5,053
Total accruing loans which are contractually past due 90 days or more	17	68
Commercial Real Estate Owner Occupied
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	1,739	2,742
Commercial Real Estate Non Owner Occupied
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	2,659	434
Commercial real estate portfolio
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	4,398	3,176
Construction portfolio
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	429	0
Residential real estate portfolio
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	1,598	1,427
Commercial and industrial portfolio
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	7,270	447
Total accruing loans which are contractually past due 90 days or more	5	56
Consumer portfolio
Financing Receivable, Impaired [Line Items]
Total non-accrual loans	0	3
Total accruing loans which are contractually past due 90 days or more	$ 12	$ 12