Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Receivables [Abstract]
Deferred loan fees	$ 73,700	$ 73,300
Discounts on acquired loans	5,600	9,500
Total loans pledged to secure borrowings	12,300,000
Outstanding contractual unpaid principal balance of non-covered purchased impaired loans	231,000	252,500
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans acquired with deteriorated credit quality	$ 173,492	$ 189,100	$ 260,259