Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 53	$ 29	$ 151	$ 63
Loans Held For Sale [Member] | Commercial Mortgages [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	46	25	106	48
Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	5	7	31	16
Other Assets Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 3	$ 3	$ (24)	$ 24