Other Financial Information - Other Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid expenses	$ 290	$ 274
Income tax receivable	7	35
Materials, supplies and inventory	105	105
Contract assets	66	42
Other	53	70
Total other current assets	808	819
Acquisition Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	173	178
Fulfillment Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	$ 114	$ 115

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer; classified as current.

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Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

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The carrying amount of capitalized costs of materials, supplies, and other assets, which are not included in inventory but used in production.

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Amount of current assets classified as other.

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Amount of other miscellaneous assets expected to be realized or consumed within one year or operating cycle, if longer.

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Net amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies.

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Amount of asset related to consideration paid in advance for costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

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