Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans Held For Sale | Residential Mortgage
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 38	$ 121	$ 152
Loans Held For Sale | Commercial Mortgage
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	67	87	76
Loans | Residential Mortgage
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	24	27	30
Other Assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ (40)	$ 60	$ 50