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Fair Value Measurements and Derivative Instruments - Schedule of Outstanding Fuel Swap Agreements (Details) - Fuel Swap Agreements
$ in Millions
Mar. 31, 2025
USD ($)
T
Dec. 31, 2024
USD ($)
T
Derivative Instruments    
Estimated unrealized net gain (loss) associated with cash flow hedges pertaining to fuel swap agreements expected to be reclassified to earnings from accumulated other comprehensive income loss | $ $ 2 $ 9
2025    
Derivative Instruments    
Fuel swap agreements (metric tons) 767,499 1,031,449
Percentage of projected requirements 59.00% 60.00%
2026    
Derivative Instruments    
Fuel swap agreements (metric tons) 982,050 786,750
Percentage of projected requirements 55.00% 44.00%
2027    
Derivative Instruments    
Fuel swap agreements (metric tons) 728,048 364,048
Percentage of projected requirements 40.00% 20.00%
2028    
Derivative Instruments    
Fuel swap agreements (metric tons) 94,699 0
Percentage of projected requirements 5.00% 0.00%