Income Taxes - Summary of Activity Related to Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 94	$ 71	$ 63
Decrease related to agreements with tax authorities	(40)	(14)	(13)
Increase related to tax positions taken during current year	12	26	7
Increase related to tax positions taken during prior years	44	11	14
Decreases related to a lapse of the applicable statute of limitations	(2)	0	0
Ending balance	$ 108	$ 94	$ 71

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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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

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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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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