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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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 241,979		$ 241,979		$ 241,444
Assets Derivatives	2,545		2,545		1,233
Liability Derivatives	929		929		523
Interest rate derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	213,698		213,698		214,805
Assets Derivatives	2,151		2,151		981
Liability Derivatives	756		756		446
Interest rate derivative contracts \| Cash Flow Hedges \| Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	9,509		9,509		13,319
Assets Derivatives	0		0		0
Liability Derivatives	1		1		0
Commodity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	4		4		9
Assets Derivatives	0		0		0
Liability Derivatives	0		0		0
Foreign exchange derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	16,842		16,842		11,219
Assets Derivatives	372		372		230
Liability Derivatives	157		157		64
Equity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	148		148		72
Assets Derivatives	6		6		8
Liability Derivatives	7		7		8
Other derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	57		57		72
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	230,749		230,749		226,177
Assets Derivatives	2,529		2,529		1,219
Liability Derivatives	920		920		518
Other Risk Management \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	1,721		1,721		1,948
Assets Derivatives	16		16		14
Liability Derivatives	8		8		$ 5
Net gains (losses) on derivatives included in other noninterest income	$ 1	$ 5	$ 29	$ (2)