Fair Value (Fair Value Option - Changes in Fair Value) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Loans held for sale | Residential mortgage loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) - FVO: changes in fair value	$ 47	$ 53	$ 120	$ 151
Loans held for sale | Commercial mortgage loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) - FVO: changes in fair value	31	46	77	106
Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) - FVO: changes in fair value	21	5	52	31
Other assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) - FVO: changes in fair value	$ 3	$ 3	$ 25	$ (24)