Intangible Assets (Summary Of Gross Goodwill And Accumulated Impairment Losses And Write-Offs Detailed By Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill [Line Items]
Goodwill, Beginning balance	$ 1,386,853	$ 191,371
Additions	11,648	0
Goodwill, Ending balance	1,398,501	191,371
Regional Banking
Goodwill [Line Items]
Goodwill, Beginning balance	1,243,885	93,367
Additions	11,648	0
Goodwill, Ending balance	1,255,533	93,367
Fixed Income
Goodwill [Line Items]
Goodwill, Beginning balance	142,968	98,004
Additions	0	0
Goodwill, Ending balance	$ 142,968	$ 98,004