Loans and reserve for credit losses (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	$ 12,483	$ 5,053
Total accruing loans which are contractually past due 90 days or more	59	68
Commercial real estate: | Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	1,353	2,742
Commercial real estate: | Non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	2,711	434
Commercial real estate: | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	4,064	3,176
Construction | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	39	0
Total accruing loans which are contractually past due 90 days or more	21	0
Residential real estate | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	1,443	1,427
Commercial and industrial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	6,937	447
Total accruing loans which are contractually past due 90 days or more	12	56
Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	0	3
Total accruing loans which are contractually past due 90 days or more	$ 26	$ 12