Derivative Instruments and Hedging Activities (Fair Value Amounts of Derivative Instruments Reported on our Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	$ 70	$ 39
Fair value of derivative contracts in a payable position	70	41
Derivative, notional amount	43,486	23,762
Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	0	0
Fair value of derivative contracts in a payable position	1	1
Derivative, notional amount	29,200	7,051
Not designated as hedging instrument \| Other trading
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	70	39
Fair value of derivative contracts in a payable position	69	40
Derivative, notional amount	14,286	16,711
Interest rate swaps \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	0	0
Fair value of derivative contracts in a payable position	0	0
Derivative, notional amount	29,050	6,915
Foreign exchange forwards \| Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	0	0
Fair value of derivative contracts in a payable position	1	1
Derivative, notional amount	150	136
Interest rate contracts \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	69	39
Fair value of derivative contracts in a payable position	69	39
Derivative, notional amount	14,094	16,587
Interest rate contracts \| Not designated as hedging instrument \| Futures and forwards
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	0	0
Fair value of derivative contracts in a payable position	0	0
Derivative, notional amount	9	23
Interest rate contracts \| Not designated as hedging instrument \| Written options
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	1	1
Fair value of derivative contracts in a payable position	69	39
Derivative, notional amount	7,074	8,327
Interest rate contracts \| Not designated as hedging instrument \| Purchased options
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	68	38
Fair value of derivative contracts in a payable position	0	0
Derivative, notional amount	7,011	8,237
Foreign exchange contracts \| Not designated as hedging instrument
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	1	0
Fair value of derivative contracts in a payable position	0	1
Derivative, notional amount	192	124
Foreign exchange contracts \| Not designated as hedging instrument \| Foreign exchange forwards
Derivatives, Fair Value [Line Items]
Derivative contracts in a receivable position, fair value	1	0
Fair value of derivative contracts in a payable position	0	1
Derivative, notional amount	$ 192	$ 124

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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