Derivatives - Classification of Gross Fair Values of Derivative Instruments, Excluding Cash Collateral (Detail) - Commodity derivatives - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
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|---|---|---|---|---|---|
| Other current assets | |||||
| Derivatives, Fair Value [Line Items] | |||||
| Asset | $ 21 | $ 127 | |||
| Liability | 60 | 126 | |||
| Other current liabilities(a) | |||||
| Derivatives, Fair Value [Line Items] | |||||
| Asset | 0 | 0 | |||
| Liability | [1] | 12 | 14 | ||
| Deferred credits and other liabilities | |||||
| Derivatives, Fair Value [Line Items] | |||||
| Asset | 0 | 0 | |||
| Liability | [1] | $ 48 | $ 52 | ||
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