Investment in Equity Method Affiliate - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Equity Method Investments [Line Items]
Amount billed associated with service agreements	$ 596	$ 699	$ 1,759	$ 2,229
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	$ 3	$ 2	$ 11	$ 12