Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 46	$ 14
Loans Held For Sale [Member] | Commercial Mortgages [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	48	5
Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	18	4
Other Assets Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ (36)	$ 9