Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Assets [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ (1)	$ 16	$ (11)	$ 36
Other liabilities [Member]
Gains (Losses) - FVO: Changes in Fair Value	(3)	(5)	(8)	(24)
Residential Mortgage [Member] | Loans Held For Sale [Member]
Gains (Losses) - FVO: Changes in Fair Value	13	39	25	101
Residential Mortgage [Member] | Loans [Member]
Gains (Losses) - FVO: Changes in Fair Value	7	7	17	18
Commercial Mortgages [Member] | Loans Held For Sale [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ 16	$ 15	$ 41	$ 58