Derivative Instruments and Other Financial Instruments Used For Hedging - Notional Amounts and Fair Value Amounts of Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 119,015		$ 119,015		$ 150,854
Assets Derivatives	807		807		1,322
Liability Derivatives	934		934		1,127
Interest rate derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	108,129		108,129		132,214
Assets Derivatives	469		469		878
Liability Derivatives	688		688		646
Interest rate derivative contracts | Cash Flow Hedges | Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	181		181		6,998
Assets Derivatives	4		4		2
Liability Derivatives	0		0		149
Interest rate derivative contracts | Fair value hedges | Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	0		0		500
Assets Derivatives	0		0		0
Liability Derivatives	0		0		0
Commodity derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	569		569		1,244
Assets Derivatives	43		43		50
Liability Derivatives	32		32		33
Foreign exchange derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	7,975		7,975		7,053
Assets Derivatives	238		238		250
Liability Derivatives	140		140		146
Equity derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	815		815		1,496
Assets Derivatives	52		52		139
Liability Derivatives	52		52		144
Other derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	46		46		4
Assets Derivatives	0		0		0
Liability Derivatives	0		0		0
Trading derivatives | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	117,534		117,534		142,011
Assets Derivatives	802		802		1,317
Liability Derivatives	912		912		969
Other Risk Management | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	1,300		1,300		1,345
Assets Derivatives	1		1		3
Liability Derivatives	22		22		$ 9
Net gains (losses) on derivatives included in other noninterest income	$ (49)	$ 10	$ 2	$ 6