Income Taxes (Changes in Liability for Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance of gross unrecognized tax benefits	$ 130	$ 207	$ 18
Increases: Positions taken during a current period	265
Increases: Positions taken during a prior period			212
Decreases: Positions taken during a prior period		(77)	(16)
Decreases: Settlements with taxing authorities	(130)		(7)
Ending balance of gross unrecognized tax benefits	265	130	207
Favorable impact if recognized	$ 209	$ 76	$ 76

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

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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