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Income Taxes - Schedule of Reserve for Uncertain Tax Positions That May BE Challenged (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits, beginning of period	$ 257	$ 102
Gross increases:
Current year tax positions	7	43
Prior year tax positions	14	113
Gross decreases:
Statute of limitation lapses	(1)	(1)
Gross unrecognized tax benefits, end of period	$ 277	$ 257

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Gross Decreases [Abstract]

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Gross Increases [Abstract]

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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 unrecognized tax benefits.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
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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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