Derivatives and Risk Management Activities - Offsetting (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative Asset Positions
Effect of Collateral Netting (Asset)		$ (45)
Derivative Liability Positions
Effect of Collateral Netting (Liability)	$ 318
Commodity Derivatives
Derivative Asset Positions
Effect of Collateral Netting (Asset)		(45)
Derivative Liability Positions
Gross Position - Asset	85	235
Gross Position - Liability	(386)	(105)
Effect of Collateral Netting (Liability)	318
Net Carrying Value Presented on the Balance Sheet, Total	17	85
Other current assets | Commodity Derivatives
Derivative Asset Positions
Gross Position - Asset	71	179
Gross Position - Liability	(314)	(37)
Effect of Collateral Netting (Asset)		(45)
Net Carrying Value Presented on the Balance Sheet	75	97
Derivative Liability Positions
Effect of Collateral Netting (Liability)	318
Other long-term assets, net | Commodity Derivatives
Derivative Asset Positions
Gross Position - Asset	5	24
Gross Position - Liability	0	0
Net Carrying Value Presented on the Balance Sheet	5	24
Other current liabilities | Commodity Derivatives
Derivative Liability Positions
Gross Position - Asset	9	32
Gross Position - Liability	(40)	(56)
Net Carrying Value Presentation on the Balance Sheet	(31)	(24)
Other long-term liabilities and deferred credits | Commodity Derivatives
Derivative Liability Positions
Gross Position - Asset	0	0
Gross Position - Liability	(32)	(12)
Net Carrying Value Presentation on the Balance Sheet	$ (32)	$ (12)