Derivative Financial Instruments - Net Gains (Losses) Recorded in the Condensed Consolidated Statements of Income Relating to Free-Standing Derivative Instruments Used for Risk Management and Other Business Purposes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (11)	$ (12)	$ (99)	$ 348
Forward contracts related to residential mortgage loans held for sale | Mortgage banking net revenue | Residential mortgages held for sale
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	23	7	32	(4)
Interest rate contracts | Mortgage banking net revenue | MSR portfolio
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(11)	(12)	(99)	348
Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	3	(3)	(3)	4
Equity contracts | Other noninterest income | Swap
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (17)	$ (22)	$ (67)	$ (73)