Description of Business, Accounting Policies, and Supplemental Disclosures - Foreign Currency (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Transaction gain (loss) arising from intercompany foreign currency transactions	$ 118	$ 95	$ (186)

Amount of cumulative translation gain (loss), before tax, from translating foreign currency financial statements into the reporting currency.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration