Loans (Change in accretable yield on acquired loans narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 61,221		$ 61,221		$ 55,686
Provision for loan losses	5,238	$ 5,705	14,332	$ 10,235
2015, 2016 and 2017 Acquisitions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	36,900		36,900
Estimated fair value of loans acquired	21,800		21,800
Allowance for loan and lease losses	675		675		$ 139
Provision for loan losses			675	$ 5
2015 Acquisitions | Non Impaired Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	3,670,000		3,670,000
Estimated fair value of loans acquired	$ 3,590,000		$ 3,590,000