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Related Party Expenses (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025
Related Party Transaction [Line Items] |  |  |  |
General and administrative expenses | $ 108 | $ 107 | $ 222 | $ 219
Marathon Petroleum Corporation [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
General and administrative expenses | 82 | 81 | 170 | 156
Asset under Construction [Member] | Marathon Petroleum Corporation [Member] |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Property, Plant, and Equipment, before Accumulated Depreciation, Addition | $ 64 | $ 46 | $ 117 | $ 95

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