Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 661	$ 344	$ 307
Additions based on tax positions related to the current year	4	1	62
Additions based on tax positions related to prior years	115	324	32
Reductions for tax positions of prior years	(111)	(5)	(28)
Expiration of statutes of limitation	(7)	(2)	(10)
Settlements	(7)	(1)	(19)
Ending balance	$ 655	$ 661	$ 344

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 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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