Securitization Activities (Summary Of Retained Interests In SPEs) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Residential Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency residential mortgage-backed securities	$ 16,661.6	$ 10,901.9
Retained Interests	32.6	203.6
Commercial Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency commercial mortgage-backed securities	4,027.5	2,313.4
Retained Interests	22.7	87.2
CLOs [Member]
Securitization Activities [Line Items]
CLOs	3,747.5	4,538.4
Retained Interests	55.9	51.5
Consumer and Other Loans [Member]
Securitization Activities [Line Items]
Retained Interests	31.2	31.0
Consumer and Other Loans Securitization Assets	$ 737.3	$ 655.0