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Financial Instruments (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Short-term investments [Abstract] |  |
Short-term investments reclassified as other assets | $ 10,000,000 |
Short-term investments | 60,000,000 | $ 60,000,000
Transfers out of level 2 | 0 |
Fair Value of Debt Instruments [Abstract] |  |
Fair value of total debt | 31,900,000,000 | 27,200,000,000
Fair value of total debt in excess (less than) of carrying value | 5,100,000,000 | $ 2,000,000,000.0
Time Deposits [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |
Short-term investments [Abstract] |  |
Short-term investments | $ 70,000,000 |

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