Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 52	$ 20	$ 98	$ 34
Loans Held For Sale [Member] | Commercial Mortgages [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	12	18	60	23
Loans [Member] | Residential Mortgage [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	8	5	26	9
Other Assets Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (Losses) - FVO: Changes in Fair Value	$ 9	$ 12	$ (27)	$ 21