Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Total foreign currency forward-exchange contracts	$ 20	$ (25)
Foreign Exchange Forward \| Derivatives Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Total foreign currency forward-exchange contracts	6	(2)
Gain (loss) on derivative contracts not designated as hedging instruments	(2)	0
Foreign Exchange Forward \| Derivatives Not Designated as Hedging Instruments \| Other current assets
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	(10)	(7)
Foreign Exchange Forward \| Derivatives Not Designated as Hedging Instruments \| Other current liabilities
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	(16)	(5)
Forward Starting Interest Rate Swap Contract [Member] \| Derivatives Designated as Hedging Instruments \| Other non-current assets
Derivatives, Fair Value [Line Items]
Total foreign currency forward-exchange contracts	(6)	(5)
Forward Starting Interest Rate Swap Contract [Member] \| Derivatives Designated as Hedging Instruments \| Other non-current liabilities
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	(17)	(1)
Cross-currency interest rate swap contracts \| Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Unrecognized net gains/(losses) on derivative instruments	(58)	12
Gains/(losses) on derivative instruments	18	19
Collateral received	8
Cross-currency interest rate swap contracts \| Derivatives Designated as Hedging Instruments \| Other current assets
Derivatives, Fair Value [Line Items]
Total foreign currency forward-exchange contracts	(2)	(4)
Cross-currency interest rate swap contracts \| Derivatives Designated as Hedging Instruments \| Other current liabilities
Derivatives, Fair Value [Line Items]
Total foreign currency forward-exchange contracts	(21)	(3)
Cross-currency interest rate swap contracts \| Derivatives Designated as Hedging Instruments \| Other non-current assets
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	(5)	(20)
Fixed to Floating Interest Rate Swap [Member] \| Derivatives Designated as Hedging Instruments \| Other non-current liabilities
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	11	(2)
Forward starting interest rate swap contracts \| Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Foreign currency forward-exchange contracts	(14)	23
Unrecognized net gains/(losses) on derivative instruments	$ (11)	$ 3

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

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