Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details) - Risk Management Activities - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Derivatives gains/(losses) recorded in income	$ 320	$ 596	$ 823	$ 2,571
Interest rate
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Derivatives gains/(losses) recorded in income	320	597	822	2,533
Credit
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Derivatives gains/(losses) recorded in income	(14)	(19)	(81)	(58)
Foreign exchange
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Derivatives gains/(losses) recorded in income	$ 14	$ 18	$ 82	$ 96