Securitization Activities (Summary Of Retained Interests In SPEs) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Residential Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency residential mortgage-backed securities	$ 4,930.1	$ 7,584.9
Retained Interests	8.6	31.0
Commercial Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency commercial mortgage-backed securities	2,292.5	1,806.3
Retained Interests	33.8	29.6
CLOs [Member]
Securitization Activities [Line Items]
CLOs	2,759.5	4,102.2
Retained Interests	7.1	37.0
Consumer and Other Loans [Member]
Securitization Activities [Line Items]
Retained Interests	67.4	25.3
Consumer and Other Loans Securitization Assets	$ 365.3	$ 395.7