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Financial Instruments - Long-term Debt Maturity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 20, 2018	Sep. 12, 2017	Nov. 13, 2015	Jan. 28, 2013
Debt Instrument [Line Items]
Current portion of long-term debt	$ 1,100		$ 1,100		$ 500
2020	500		500
2021	600		600
2022	0		0
2023	1,350		1,350
2024	0		0
After 2024	5,300		5,300
Total long-term debt	7,750		7,750		$ 6,500
Interest expense, net of capitalized interest	62	$ 56	173	$ 167
Capitalized interest	$ 4	$ 3	$ 12	$ 9
Senior Notes
Debt Instrument [Line Items]
Total long-term debt						$ 1,500	$ 1,250	$ 1,250	$ 3,650