Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Loans Held For Sale [Member] | Residential Mortgage [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ 39	$ 55	$ 101	$ 161
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Gains (Losses) - FVO: Changes in Fair Value	15	16	58	65
Loans [Member] | Residential Mortgage [Member]
Gains (Losses) - FVO: Changes in Fair Value	7	7	18	24
Other Assets [Member]
Gains (Losses) - FVO: Changes in Fair Value	16	$ 26	36	$ (4)
Other liabilities [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ (5)		$ (24)