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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (11)	$ (12)	$ (99)	$ 348
Interest rate contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	8	5	27	31
Interest rate contracts | Credit losses | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	0	(1)	0	(1)
Interest rate contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	2	1	19	(33)
Interest rate contracts | Interest rate lock commitments | Mortgage banking net revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	44	54	132	237
Commodity contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	6	4	17	10
Commodity contracts | Credit losses | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	0	0	0	(1)
Commodity contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(1)	(1)	(1)	(2)
Foreign exchange contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	3	(3)	(3)	4
Foreign exchange contracts | Contract revenue | Commercial banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	15	14	45	40
Foreign exchange contracts | Contract revenue | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	2	(6)	2	(3)
Foreign exchange contracts | Credit portion of fair value adjustment | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 0	$ 1	$ 0	$ (1)