Fair Value Measurements, Derivative Assets & Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Cumulative Amount of Fair Value Hedging Adjustment - Increase (Decrease) Included in Carrying Amount of Liability	$ (132)	$ (70)
Long-term Obligations [Member]
Derivatives, Fair Value [Line Items]
Hedged Liability, Fair Value Hedge	3,250	3,309
Cumulative Amount of Fair Value Hedging Adjustment - Increase (Decrease) Included in Carrying Amount of Liability	(132)	(70)
Hedged Liability, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	37	43
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount Of Derivatives	3,100	3,100
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instrument [Member] \| Other Long-term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	172	124
Cross Currency Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Notional Amount Of Derivatives	1,200
Cross Currency Interest Rate Contract [Member] \| Derivatives Designated as Hedging Instrument [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	6
Currency Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount Of Derivatives	1,974	2,921
Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instrument [Member] \| Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	3	10
Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instrument [Member] \| Other Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	4	15
Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	9	10
Derivative Liabilities	$ 176	$ 139

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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