Derivatives and Risk Management Activities - Offsetting Asset and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative Asset Positions
Effect of Collateral Netting (Asset)		$ (45)
Derivative Liability Positions
Effect of Collateral Netting (Liability)	$ 133
Commodity Derivatives
Derivative Asset Positions
Effect of Collateral Netting (Asset)		(45)
Derivative Liability Positions
Gross Position - Asset	219	235
Gross Position - Liability	(296)	(105)
Effect of Collateral Netting (Liability)	133
Net Carrying Value Presented on the Balance Sheet, Total	56	85
Other current assets | Commodity Derivatives
Derivative Asset Positions
Gross Position - Asset	117	179
Gross Position - Liability	(80)	(37)
Effect of Collateral Netting (Asset)		(45)
Net Carrying Value Presented on the Balance Sheet	99	97
Derivative Liability Positions
Effect of Collateral Netting (Liability)	62
Other long-term assets, net | Commodity Derivatives
Derivative Asset Positions
Gross Position - Asset	63	24
Gross Position - Liability	(3)
Net Carrying Value Presented on the Balance Sheet	60	24
Other current liabilities | Commodity Derivatives
Derivative Liability Positions
Gross Position - Asset	31	32
Gross Position - Liability	(151)	(56)
Effect of Collateral Netting (Liability)	71
Net Carrying Value Presented on the Balance Sheet	(49)	(24)
Other long-term liabilities and deferred credits | Commodity Derivatives
Derivative Liability Positions
Gross Position - Asset	8
Gross Position - Liability	(62)	(12)
Net Carrying Value Presented on the Balance Sheet	$ (54)	$ (12)