Fair Value of Assets and Liabilities - Narrative (Details) - Corporate - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Fixed asset impairments	$ 1	$ 5	$ 33	$ 6
Asset impairment charges			35
2019 Business Optimization \| Disposition of Acquired Properties
Segment Reporting Information [Line Items]
Asset impairment charges	$ 1	$ 4	$ 3	$ 4

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value.

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