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Fair Value Measurements (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Fair Value Disclosures [Abstract]    
Cash $ 629 $ 168
Cash and Cash Equivalents [Abstract]    
Cash and cash equivalents, fair value 1,982 1,614
Total cash and cash equivalents 1,982 1,614
U.S. and Canadian government obligations    
Cash and Cash Equivalents [Abstract]    
Cash and cash equivalents, adjusted cost 284 932
Cash equivalents, fair value 284 932
Other debt obligations    
Cash and Cash Equivalents [Abstract]    
Cash and cash equivalents, adjusted cost 1,069 514
Cash equivalents, fair value 1,069 514
Nonqualified employee benefit trusts    
Cash and Cash Equivalents [Abstract]    
Available-for-sale securities, amortized cost 15 15
Unrealized Gains 3 2
Unrealized Losses 0 0
Fair Value $ 18 $ 17