Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Receivables [Abstract]
Deferred loan fees	$ 74,500	$ 67,700
Discounts on acquired loans	13,100	41,300
Total loans pledged to secure borrowings	10,700,000
Outstanding contractual unpaid principal balance of non-covered purchased impaired loans	276,500	368,200
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans acquired with deteriorated credit quality	$ 206,604	$ 280,400	$ 301,314