Loans (Change in accretable yield on acquired loans) (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 58,656,000		$ 55,686,000
Provision for loan losses	4,263,000	$ 3,641,000
2015, 2016 and 2017 Acquisitions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	26,000,000
Estimated fair value of loans acquired	15,000,000
Allowance for loan and lease losses	0		$ 139,000
Provision for loan losses	0	$ 1,000
Non Impaired Purchased Loans | Two Thousand Fifteen Acquisitions [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	2,990,000,000
Estimated fair value of loans acquired	$ 2,910,000,000