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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (12)	$ 130	$ 348	$ 308
Interest rate contracts | Mortgage banking net revenue | Forward contracts | Residential mortgages held for sale
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	7	11	(4)	6
Interest rate contracts | Mortgage banking net revenue | MSR portfolio
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(12)	130	348	308
Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(3)	2	4	(3)
Equity contracts | Other noninterest income | Swap
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (22)	$ (11)	$ (73)	$ (63)