Acquisitions and Divestitures (Schedule of Divestiture-related Charges) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Restructuring Charges	$ 79	$ 159	$ 0
Asset divestiture-related charges	0	25	170
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning employee-related obligations	6	27
Restructuring Charges	79	181
Cash payments	78	176
Ending employee-related obligations	3	6	27
Restructuring Reserve	3	27	$ 27
Employee Severance [Member] \| 2019 Corporate Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring Charges	0	159
One-time Termination Benefits [Member] \| 2019 Corporate Restructuring [Member]
Restructuring Reserve [Roll Forward]
Noncash stock-based compensation	$ 4	$ 26

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- Definition

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

+ References

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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