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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Trading Derivatives
Trading account activities	$ (3)	$ 25	$ (10)	$ 93
Trading derivatives
Trading Derivatives
Trading account activities	0	55	(36)	65
Trading derivatives | Interest rate derivative contracts
Trading Derivatives
Trading account activities	(11)	12	(69)	(6)
Trading derivatives | Equity contracts
Trading Derivatives
Trading account activities	0	31	0	40
Trading derivatives | Foreign exchange derivative contracts
Trading Derivatives
Trading account activities	11	11	32	29
Trading derivatives | Commodity
Trading Derivatives
Trading account activities	$ 0	$ 1	$ 1	$ 2