Derivatives and Hedging Activities - Fair Values, Volume of Activity and Gain (Loss) Information Related to Derivative Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Notional Amount	$ 122,771	$ 102,645
Derivative assets, netting adjustments	(413)	(333)
Derivative Assets, net	806	529
Derivative liabilities, netting adjustments	(319)	(337)
Derivative Liabilities, net	171	353
Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	37,269	28,668
Derivative Assets	105	52
Derivative Liabilities	12	(10)
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	85,502	73,977
Derivative Assets	1,117	812
Derivative Liabilities	524	733
Interest Rate [Member] \| Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	37,147	28,546
Derivative Assets	105	50
Derivative Liabilities	10	(10)
Interest Rate [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	68,202	63,454
Derivative Assets	784	365
Derivative Liabilities	210	307
Foreign Exchange [Member] \| Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	122	122
Derivative Assets	0	2
Derivative Liabilities	2	0
Foreign Exchange [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	5,702	6,829
Derivative Assets	70	104
Derivative Liabilities	62	95
Commodity [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	6,662	2,002
Derivative Assets	246	333
Derivative Liabilities	236	323
Credit [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	453	226
Derivative Assets	1	1
Derivative Liabilities	3	1
Other [Member] \| Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	4,483	1,466
Derivative Assets	16	9
Derivative Liabilities	13	7
Net Derivatives [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	122,771	102,645
Derivative Assets, net	809	531
Derivative Liabilities, net	217	386
Counterparty And Cash Collateral Netting [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	0	0
Derivative Assets, net	(3)	(2)
Derivative Liabilities, net	$ (46)	$ (33)

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