Asset Retirement Obligations and Accrued Environmental Costs - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Site Contingency [Line Items]
Asset retirement balance increase for the period	$ (50)
Changes in estimates of existing obligations	81	$ 33
New obligations	42	261
Accrued environmental costs	506	$ 439
Acquired through Business Combination
Site Contingency [Line Items]
Accrued environmental costs	304
Expected future undiscounted payments related to the portion of the accrued environmental costs that have been discounted
Expected future undiscounted payments, due in 2026	35
Expected future undiscounted payments, due in 2027	24
Expected future undiscounted payments, due in 2028	28
Expected future undiscounted payments, due in 2029	34
Expected future undiscounted payments, due in 2030	24
Expected future undiscounted payments, due for all future years after 2030	$ 230
Weighted Average \| Acquired through Business Combination
Site Contingency [Line Items]
Accrued environmental costs, discount rate, percent	5.00%
Domestic Refineries and Underground Sites
Site Contingency [Line Items]
Accrued environmental costs	$ 373
Nonoperator sites
Site Contingency [Line Items]
Accrued environmental costs	96
Other sites
Site Contingency [Line Items]
Accrued environmental costs	$ 37

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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