Loans (Change in accretable yield on acquired loans) (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 61,324,000		$ 61,324,000		$ 55,686,000
Provision for loan losses	4,831,000	$ 889,000	9,094,000	$ 4,530,000
2015, 2016 and 2017 Acquisitions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	36,900,000		36,900,000
Estimated fair value of loans acquired	21,800,000		21,800,000
Allowance for loan and lease losses	672,000		672,000		$ 139,000
Provision for loan losses			672,000	$ 1,000
Non Impaired Purchased Loans | 2015 Acquisitions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	3,670,000,000		3,670,000,000
Estimated fair value of loans acquired	$ 3,590,000,000		$ 3,590,000,000