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Financial Instruments (Derivative) (Details) $ in Millions	6 Months Ended
Financial Instruments (Derivative) (Details) $ in Millions	Jun. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / lb	Dec. 31, 2019 USD ($)
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		$ 7,672	$ 3,657
Restricted Cash and Cash Equivalents, Current		114	97
Restricted Cash and Cash Equivalents, Noncurrent		133	149
Total cash, cash equivalents, restricted cash and restricted cash equivalents presented in the consolidated statements of cash flows		7,919	3,903	$ 2,655	$ 2,278
Credit Derivative, Maximum Exposure, Undiscounted		37
Forward Contracts [Member]
Cash and Cash Equivalents [Line Items]
Derivative, Forward Price \| $ / lb				2.34
Derivative financial instruments	$ 24
Bank Time Deposits [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		$ 200	$ 300