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Financial Instruments (Interest Rate Risk) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) swap	Aug. 20, 2018 USD ($)	Sep. 12, 2017 USD ($)	Nov. 13, 2015 USD ($)	Jan. 28, 2013 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Less current portion of long-term debt	$ 600		$ 500
Debt, principal amount	7,250		6,500
Senior Notes
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt, principal amount				$ 1,500	$ 1,250	$ 1,250	$ 3,650
Senior Notes \| 4.500% 2015 senior notes due 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt, stated interest percentage rate						4.50%
Debt, principal amount	750		750
Senior Notes \| Senior Notes 2.000% Due 2030
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt, principal amount	750		0
Senior Notes \| Senior Notes 3.000% Due 2050
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt, principal amount	500		0
Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	550		$ 250
Treasury Lock
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	600
Amount of payment for settlement	6
Derivatives Designated as Hedging Instruments \| Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	350
Amount of payment for settlement	2
Number of derivative instruments \| swap			0
Derivatives Designated as Hedging Instruments \| Interest Rate Swap \| Senior Notes \| 1.875% 2013 senior notes due 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Debt, stated interest percentage rate							1.875%
Derivatives Designated as Hedging Instruments \| Treasury Lock
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount		$ 350
Derivatives Designated as Hedging Instruments \| Treasury Lock \| Senior Notes \| Senior Notes 2.000% Due 2030
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	425
Derivatives Designated as Hedging Instruments \| Treasury Lock \| Senior Notes \| Senior Notes 3.000% Due 2050
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	$ 175