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Fair Value Measurements - Fair Value of Investment Assets (Details) - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2021
--- | --- | --- | ---
Fair Value |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | $ 174 | $ 164 |
Carrying Value |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Total investments at amortized cost | 172 |  | $ 156
Level 1 | Fair Value |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 87 |  | 75
Level 1 | Fair Value | Fixed Income Mutual Funds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 87 |  | 75
Level 1 | Fair Value | Corporate Bonds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 0 |  | 0
Level 1 | Fair Value | Government Securities |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 0 |  | 0
Level 1 | Fair Value | Commercial Paper |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 0 |  | 0
Level 2 | Fair Value |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 87 |  | 89
Level 2 | Fair Value | Fixed Income Mutual Funds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 0 |  | 0
Level 2 | Fair Value | Corporate Bonds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 58 |  | 63
Level 2 | Fair Value | Government Securities |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 23 |  | 26
Level 2 | Fair Value | Commercial Paper |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 6 |  | 0
Total | Fair Value |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 174 |  | 164
Total | Fair Value | Fixed Income Mutual Funds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 87 |  | 75
Total | Fair Value | Corporate Bonds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 58 |  | 63
Total | Fair Value | Government Securities |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | 23 |  | 26
Total | Fair Value | Commercial Paper |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Commercial Paper | $ 6 |  | $ 0

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