Derivative and Financial Instruments - Commodity Gain (Loss) (Details) - Commodity Contract [Member] - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2020 |
Sep. 30, 2019 |
|
| Sales and other operating revenues [Member] | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Gains (losses) from commodity derivatives | $ 33 | $ 4 | $ 30 | $ 68 |
| Other Income [Member] | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Gains (losses) from commodity derivatives | (2) | 3 | 3 | 4 |
| Purchased commodities [Member] | ||||
| Derivative Instruments, Gain (Loss) [Line Items] | ||||
| Gains (losses) from commodity derivatives | $ (27) | $ (9) | $ (29) | $ (60) |