Investment in Equity Method Affiliate - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Amount billed associated with service agreements	$ 515	$ 735	$ 1,163	$ 1,530
SESH
Schedule of Equity Method Investments [Line Items]
Percentage of distributions through limited partner interest			50.00%
SESH | Enbridge, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%		50.00%
SESH | Enable Midstream Partners, LP [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%		50.00%
SESH | Equity Method Investee | Shared Operations Service Agreements
Schedule of Equity Method Investments [Line Items]
Amount billed associated with service agreements	$ 2	$ 7	$ 8	$ 10