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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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 296,524		$ 296,524		$ 201,094
Assets Derivatives	1,637		1,637		871
Liability Derivatives	723		723		804
Interest rate derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	272,747		272,747		189,478
Assets Derivatives	1,272		1,272		531
Liability Derivatives	524		524		600
Interest rate derivative contracts \| Cash Flow Hedges \| Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	10,819		10,819		674
Assets Derivatives	0		0		6
Liability Derivatives	0		0		0
Commodity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	125		125		336
Assets Derivatives	10		10		25
Liability Derivatives	8		8		18
Foreign exchange derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	9,892		9,892		8,475
Assets Derivatives	333		333		260
Liability Derivatives	166		166		168
Equity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	107		107		300
Assets Derivatives	12		12		22
Liability Derivatives	12		12		13
Other derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	53		53		127
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	282,924		282,924		198,716
Assets Derivatives	1,627		1,627		838
Liability Derivatives	710		710		799
Other Risk Management \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	2,781		2,781		1,704
Assets Derivatives	10		10		27
Liability Derivatives	13		13		$ 5
Net gains (losses) on derivatives included in other noninterest income	$ (5)	$ 28	$ 2	$ (26)