Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Assets [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ 11	$ 7
Other liabilities [Member]
Gains (Losses) - FVO: Changes in Fair Value	(2)	(16)
Residential Mortgage [Member] | Loans Held For Sale [Member]
Gains (Losses) - FVO: Changes in Fair Value	4	30
Residential Mortgage [Member] | Loans [Member]
Gains (Losses) - FVO: Changes in Fair Value	3	4
Commercial Mortgages [Member] | Loans Held For Sale [Member]
Gains (Losses) - FVO: Changes in Fair Value	$ 14	$ 18