Derivative and Financial Instruments - Commodity Notional (Details) - Commodity Contract [Member] - Bcf |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2021 |
Dec. 31, 2020 |
|
| Natural gas and power, Fixed price [Member] | Long [Member] | ||
| Trading Activity, Gains and Losses, Net [Line Items] | ||
| Commodity derivatives - volumetric material net exposures | 10 | |
| Natural gas and power, Fixed price [Member] | Short [Member] | ||
| Trading Activity, Gains and Losses, Net [Line Items] | ||
| Commodity derivatives - volumetric material net exposures | 20 | |
| Natural gas and power, Basis [Member] | Short [Member] | ||
| Trading Activity, Gains and Losses, Net [Line Items] | ||
| Commodity derivatives - volumetric material net exposures | 19 | 10 |