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Fair Value Measurements - Schedule of Fair Value of Investment Assets (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Fair Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at fair value | $ 101 | $ 1,084
Carrying Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at amortized cost | 89 | 1,076
Level 2 | Fair Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at fair value | 101 | 1,084
Level 2 | Fair Value | Corporate Bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at fair value | 68 | 59
Level 2 | Fair Value | Government Securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at fair value | 33 | 36
Level 2 | Fair Value | Commercial Paper and Certificates of Deposit |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total investments at fair value | $ 0 | $ 989

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