Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Receivables [Abstract]
Deferred loan fees	$ 74,100	$ 73,300
Discounts on acquired loans	58,000	70,500
Total loans pledged to secure borrowings	12,500,000
Outstanding contractual unpaid principal balance of non-covered purchased impaired loans	211,300	252,500
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans acquired with deteriorated credit quality	$ 157,876	$ 189,100	$ 235,710