Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Loans and leases, deferred fees and costs	$ 73,300	$ 67,700
Discounts on acquired loans	9,500	41,300
Total loans pledged to secure borrowings	12,000,000
Outstanding contractual unpaid principal balance of non-covered purchased impaired loans	252,500	368,200
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans acquired with deteriorated credit quality	1,132,217	918,612
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans acquired with deteriorated credit quality	$ 189,113	$ 280,386