Share-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	$ 4	$ 7	$ 14	$ 20
Cash-settled
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	0	0	1	0
Unrecognized compensation costs	4		$ 4
Unrecognized compensation costs, not yet recognized			2 years
Share-settled
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense	4	$ 7	$ 13	$ 20
Unrecognized compensation costs	$ 21		$ 21
Unrecognized compensation costs, not yet recognized			2 years

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

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+ References

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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