Financial Instruments - Investments - Unrealized Gains and Losses Related to Equity Securities - Footnotes (Details) $ in Millions	Dec. 31, 2020 USD ($)
Financial Instruments [Abstract]
Cumulative impairment losses and downward price adjustments on equity securities	$ 81
Cumulative upward price adjustments on equity securities	$ 61

Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant