Income Taxes - Summary of Valuation Allowance (Details) - Valuation Allowance of Deferred Tax Assets [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1,	$ 2	$ 17	$ 50
Net charges to income tax expense	8	0	0
Release of valuation allowance	0	(15)	(33)
Balance at December 31,	$ 10	$ 2	$ 17

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 valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

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- Definition

Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

+ References

+ Details

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- Definition

Amount of decrease in valuation and qualifying accounts and reserves.

+ References

+ Details

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- Details

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