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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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 219,320		$ 219,320		$ 241,444
Assets Derivatives	2,690		2,690		1,233
Liability Derivatives	981		981		523
Interest rate derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	192,576		192,576		214,805
Assets Derivatives	2,272		2,272		981
Liability Derivatives	805		805		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	14,886		14,886		11,219
Assets Derivatives	399		399		230
Liability Derivatives	167		167		64
Equity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	84		84		72
Assets Derivatives	3		3		8
Liability Derivatives	2		2		8
Other derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	78		78		72
Assets Derivatives	0		0		0
Liability Derivatives	1		1		0
Trading derivatives \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	207,628		207,628		226,177
Assets Derivatives	2,674		2,674		1,219
Liability Derivatives	975		975		518
Other Risk Management \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	2,183		2,183		1,948
Assets Derivatives	16		16		14
Liability Derivatives	5		5		$ 5
Net gains (losses) on derivatives included in other noninterest income	$ 5	$ (16)	$ 28	$ (7)