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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 177,086		$ 177,086		$ 177,428
Assets Derivatives	1,379		1,379		1,626
Liability Derivatives	1,168		1,168		1,684
Interest rate derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	154,986		154,986		149,229
Assets Derivatives	899		899		1,074
Liability Derivatives	628		628		988
Interest rate derivative contracts | Cash Flow Hedges | Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	10,600		10,600		15,459
Assets Derivatives	2		2		19
Liability Derivatives	164		164		199
Interest rate derivative contracts | Fair value hedges | Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	500		500		500
Assets Derivatives	0		0		3
Liability Derivatives	0		0		0
Commodity derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	1,672		1,672		2,825
Assets Derivatives	74		74		145
Liability Derivatives	53		53		112
Foreign exchange derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	6,663		6,663		5,981
Assets Derivatives	241		241		217
Liability Derivatives	139		139		131
Equity derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	1,547		1,547		2,385
Assets Derivatives	162		162		165
Liability Derivatives	161		161		164
Other derivative contracts | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	79		79		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	164,947		164,947		160,424
Assets Derivatives	1,376		1,376		1,601
Liability Derivatives	981		981		1,395
Other Risk Management | Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	1,039		1,039		1,045
Assets Derivatives	1		1		3
Liability Derivatives	23		23		$ 90
Net gains (losses) on derivatives included in other noninterest income	$ (3)	$ 2	$ (9)	$ (37)