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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Trading Derivatives
Trading account activities	$ 14	$ 34		$ 70
Trading derivatives
Trading Derivatives
Trading account activities	31	(20)	$ (17)	(73)
Trading derivatives | Interest rate derivative contracts
Trading Derivatives
Trading account activities	19	(28)	(64)	(112)
Trading derivatives | Equity contracts
Trading Derivatives
Trading account activities	(1)	(6)	2	1
Trading derivatives | Foreign exchange derivative contracts
Trading Derivatives
Trading account activities	$ 13	$ 14	$ 45	$ 38