Summary of Significant Accounting Policies - Changes in Allowances for Credit Losses (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Allowance for Trade Receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at January 1, 2020	$ (35)
Current period provision for expected credit losses	(10)
Write-offs charged against the allowance	2
Currency	1
Balance at December 31, 2020	(42)
Allowance for Other Current Receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at January 1, 2020	(44)
Current period provision for expected credit losses	(1)
Write-offs charged against the allowance	2
Currency	1
Balance at December 31, 2020	(42)
Allowance for Long-Term Receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at January 1, 2020	(14)
Current period provision for expected credit losses	(1)
Write-offs charged against the allowance	0
Currency	3
Balance at December 31, 2020	$ (12)

Accounts Receivable, Allowance for Credit Loss, Foreign Currency Translation And Other

No definition available.

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of allowance for credit loss on accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of direct write-downs of accounts receivable charged against the allowance.

+ References

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- Definition

Amount of expense (reversal of expense) for expected credit loss on accounts receivable.

+ References

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