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Investments (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]      
Equity securities held $ 77 $ 45  
Purchase of long-term investments 32 22 $ 3
Debt and equity securities, unrealized gain (loss) 7    
Proceeds from the sale of long-term investments 6 10 2
Realized gain on equity securities $ 5 $ 3 $ 10