Loans and reserve for credit losses Loans and reserve for credit losses (Schedule of Financing Receivables, Post Modification) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	$ 0	$ 0
Term extension	0	22
Rate reduction and term extension	0	0
Total	0	22
Commercial real estate | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	0	0
Term extension	0	0
Rate reduction and term extension	0	0
Total	0	0
Construction | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	0	0
Term extension	0	0
Rate reduction and term extension	0	0
Total	0	0
Residential real estate | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	0	0
Term extension	0	0
Rate reduction and term extension	0	0
Total	0	0
Commercial and industrial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	0	0
Term extension	0	22
Rate reduction and term extension	0	0
Total	0	22
Consumer | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Rate reduction	0	0
Term extension	0	0
Rate reduction and term extension	0	0
Total	$ 0	$ 0