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Financial Instruments (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2021 | Jun. 30, 2021 | Dec. 31, 2020
Short-Term Investments [Abstract] |  |  |
Short-term investments | $ 46 | $ 46 | $ 60
Fair Value of Debt Instruments [Abstract] |  |  |
Fair value of total debt | 31,200 | 31,200 | 31,900
Fair value of total debt in excess of (less than) carrying value | 2,400 | 2,400 | $ 5,100
Equity Securities, FV-NI, Gain (Loss) [Abstract] |  |  |
Unrealized gain (loss) on fair value of equity investments | 20 | 20 |
Significant Other Observable Inputs (Level 2) [Member] | Time Deposits [Member] |  |  |
Short-Term Investments [Abstract] |  |  |
Short-term investments | $ 46 | $ 46 |

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