Derivative and Financial Instruments - Commodity Notional (Details) - Commodity Contract [Member] - Short [Member] - Bcfe Bcfe in Billions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Natural gas and power, Fixed price [Member] | ||
| Trading Activity, Gains and Losses, Net [Line Items] | ||
| Commodity derivatives - volumetric material net exposures | (5) | (17) |
| Natural gas and power, Basis [Member] | ||
| Trading Activity, Gains and Losses, Net [Line Items] | ||
| Commodity derivatives - volumetric material net exposures | (23) | (1) |