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Commitments and Contingencies - RFS (Details) - Petroleum Segment - Environmental, Health, and Safety Matters - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Loss Contingencies [Line Items]      
Expense for compliance with RFS $ 178 $ 19  
RFS obligation $ 342   $ 214