Derivative Financial Instruments - Net Gains (Losses) Recorded in the Consolidated Statements of Income Relating to Free-Standing Derivative Instruments Used For Customer Accommodation (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 | Customer contracts | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	5	12	31	30
Interest rate contracts | Credit losses | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(1)	0	(1)	0
Interest rate contracts | Fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	1	(5)	(33)	(18)
Interest rate contracts | Interest rate lock commitments | Mortgage banking net revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	54	50	237	108
Commodity contracts | Customer contracts | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	4	3	10	6
Commodity contracts | Credit losses | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	0	0	(1)	0
Commodity contracts | Fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(1)	0	(2)	0
Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(3)	2	4	(3)
Foreign exchange contracts | Customer contracts | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	14	12	40	36
Foreign exchange contracts | Customer contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(6)	7	(3)	15
Foreign exchange contracts | Fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 1	$ 0	$ (1)	$ 0