Derivative Instruments and Other Financial Instruments Used For Hedging - Gain or (Loss) Recognized in Income on Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Trading Derivatives
Trading account activities	$ 37	$ 17	$ 1	$ 36
Trading derivatives
Trading Derivatives
Trading account activities	(11)	(33)	(48)	(53)
Trading derivatives | Interest rate derivative contracts
Trading Derivatives
Trading account activities	(24)	(49)	(83)	(84)
Trading derivatives | Equity contracts
Trading Derivatives
Trading account activities	(1)	3	3	7
Trading derivatives | Foreign exchange derivative contracts
Trading Derivatives
Trading account activities	$ 14	$ 13	$ 32	$ 24