| Stock-Based Compensation - Compensation expense (Details) - USD ($) $ in Millions | 3 Months Ended | |
|---|---|---|
| Mar. 31, 2025 | Mar. 31, 2024 | |
| Stock-Based Compensation | ||
| Stock-based compensation | $ 3 | $ 7 | 
| X | ||||||||||
| 
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
 | 
| X | ||||||||||
| 
- References No definition available. 
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