Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans Held For Sale | Residential Mortgage
Gains (Losses) - FVO: Changes in Fair Value	$ 121	$ 152	$ 152
Loans Held For Sale | Commercial Mortgage
Gains (Losses) - FVO: Changes in Fair Value	87	76	96
Loans | Residential Mortgage
Gains (Losses) - FVO: Changes in Fair Value	27	30	43
Other Assets
Gains (Losses) - FVO: Changes in Fair Value	60	50	(8)
Other Liabilities
Gains (Losses) - FVO: Changes in Fair Value	$ (26)		$ 4