Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Assets and Liabilities Measured at Fair Value
Cash equivalents	$ 73	$ 89
Restricted cash equivalents	4	64
Exchangeable senior debentures	952	1,897
Quoted prices in active markets for identical assets (Level 1)
Assets and Liabilities Measured at Fair Value
Cash equivalents	73	89
Restricted cash equivalents	4	64
Significant other observable inputs (Level 2)
Assets and Liabilities Measured at Fair Value
Exchangeable senior debentures	$ 952	$ 1,897