Derivatives and Financial Instruments (Summary of Outstanding Commodity Derivative Contracts) (Details) - MMBbls MMBbls in Millions |
Mar. 31, 2020 |
Dec. 31, 2019 |
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Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||
Crude oil, refined petroleum products and NGL (millions of barrels) | (33) | (16) |