Derivatives - Effect of Commodity Derivative Instruments in Statements of Income (Detail) - Commodity derivatives - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Gain (Loss) | $ (28) | $ (8) |
| Sales and other operating revenues | ||
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Gain (Loss) | (1) | 16 |
| Cost of revenues | ||
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Gain (Loss) | $ (27) | $ (24) |