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v3.20.4

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Marketable securities, gain (loss) | $ 102 | $ 155 | $ 119

X
- Definition Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
Name: | us-gaap_MarketableSecuritiesGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration