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Sales and Other Operating Revenues - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]    
Accounts receivable $ 5,375 $ 3,911
Receivables from contracts with customers $ 414 $ 404
Minimum    
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]    
Customer contracts, term 5 years  
Maximum    
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]    
Customer contracts, term 15 years