Securitization Activities (Summary Of Retained Interests In SPEs) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Residential Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency residential mortgage-backed securities	$ 16,082.4	$ 10,901.9
Retained Interests	76.0	203.6
Commercial Mortgage-Backed Securities [Member]
Securitization Activities [Line Items]
U.S. government agency commercial mortgage-backed securities	3,159.2	2,313.4
Retained Interests	19.0	87.2
Collateralized Loan Obligations Securitizations [Member]
Securitization Activities [Line Items]
Collateralized loan obligations	4,219.9	4,538.4
Retained Interests	50.9	51.5
Consumer and Other Loans [Member]
Securitization Activities [Line Items]
Retained Interests	33.8	31.0
Consumer and Other Loans Securitization Assets	$ 757.1	$ 655.0