Derivatives and Risk Management Activities - Preferred Distribution Rate (Details) - Preferred Distribution Rate Reset Option - Derivatives Not Designated as a Hedge - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other long-term liabilities and deferred credits
Derivatives and Risk Management Activities
Derivative liability	$ 14	$ 34
Other income/(expense), net
Derivatives and Risk Management Activities
Gain/(loss) recognized	$ 20	$ 2	$ (14)