Derivative Instruments - Summary of Effects of Undesignated Derivatives on Consolidated Statements of Operations (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain on derivatives	$ 0	$ 0	$ (1)	$ 4
Energy derivative
Derivative Instruments, Gain (Loss) [Line Items]
Electricity sales	0	2	0	(2)
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain on derivatives	$ 3	$ 1	$ 4	$ 12

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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-Topic 815
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-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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Amount of gain (loss) included in earnings for the period from the increase (decrease) in fair value of interest rate derivatives not designated as hedging instruments.

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives not designated as hedging instruments.

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