Asset Retirement Obligations and Accrued Environmental Costs (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| Environmental Liabilities [Line Items] | |||
| Asset retirement obligations | $ 6,206 | $ 7,908 | $ 7,798 |
| Accrued environmental costs | 171 | 178 | |
| Total asset retirement obligations and accrued environmental costs | 6,377 | 8,086 | |
| Asset retirement obligations and accrued environmental costs due within one year | 1,025 | 398 | |
| Long-term asset retirement obligations and accrued environmental costs | 5,352 | $ 7,688 | |
| Other accruals | |||
| Environmental Liabilities [Line Items] | |||
| Asset retirement obligations and accrued environmental costs due within one year | $ (741) |