Goodwill, Customer Relationships and Other Intangible Assets - Goodwill Activity (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
As of December 31, 2020	$ 7,405
Reclassified as held for sale	(718)
Effect of foreign currency exchange rate changes	(20)
As of September 30, 2021	6,667
Goodwill, accumulated impairment loss	$ 3,600	$ 3,700

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of transfers into (out of) an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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