Derivative Instruments (Details 4) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
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| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Gain (Loss) on Derivative Instruments, Net, Pretax | [1] | $ 244 | $ 258 | $ 400 | $ (114) | ||||||||||||
| Gain (Loss) on Sale of Derivatives | [2],[3] | 58 | 69 | 169 | 66 | ||||||||||||
| Mark-to-market gain (loss) | [4] | 186 | 189 | 231 | (180) | ||||||||||||
| Sales [Member] | |||||||||||||||||
| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Gain (Loss) on Derivative Instruments, Net, Pretax | [1],[5],[6] | 541 | 183 | 578 | (176) | ||||||||||||
| Cost of Sales [Member] | |||||||||||||||||
| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Gain (Loss) on Derivative Instruments, Net, Pretax | [1],[5],[6] | (296) | 74 | (176) | 59 | ||||||||||||
| Interest Expense [Member] | |||||||||||||||||
| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Gain (Loss) on Derivative Instruments, Net, Pretax | [1] | (1) | 1 | (2) | 3 | ||||||||||||
| Interest Rate Hedging Instruments | |||||||||||||||||
| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Mark-to-market gain (loss) | [4] | (1) | 1 | (2) | 3 | ||||||||||||
| Energy Related Derivative [Member] | |||||||||||||||||
| Summary of Derivative Instruments by Risk Exposure [Abstract] | |||||||||||||||||
| Gain (Loss) on Sale of Derivatives | [2],[3] | 58 | 69 | 169 | 66 | ||||||||||||
| Mark-to-market gain (loss) | [4] | $ 187 | $ 188 | $ 233 | $ (183) | ||||||||||||
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