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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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Derivative Instruments and Other Financial Instruments
Notional Amount	$ 327,934		$ 327,934		$ 201,094
Assets Derivatives	1,297		1,297		871
Liability Derivatives	713		713		804
Interest rate derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	312,281		312,281		189,478
Assets Derivatives	999		999		531
Liability Derivatives	515		515		600
Interest rate derivative contracts \| Cash Flow Hedges \| Designated as Hedging Instrument
Derivative Instruments and Other Financial Instruments
Notional Amount	3,597		3,597		674
Assets Derivatives	1		1		6
Liability Derivatives	0		0		0
Commodity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	189		189		336
Assets Derivatives	16		16		25
Liability Derivatives	13		13		18
Foreign exchange derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	9,040		9,040		8,475
Assets Derivatives	255		255		260
Liability Derivatives	164		164		168
Equity derivative contracts \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	114		114		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	64		64		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	321,688		321,688		198,716
Assets Derivatives	1,282		1,282		838
Liability Derivatives	704		704		799
Other Risk Management \| Not designated as hedging instruments
Derivative Instruments and Other Financial Instruments
Notional Amount	2,649		2,649		1,704
Assets Derivatives	14		14		27
Liability Derivatives	9		9		$ 5
Net gains (losses) on derivatives included in other noninterest income	$ 16	$ 49	$ 7	$ 2