Organization and Basis of Presentation (Equity Method Investees) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Investments	$ 1,862	$ 1,771	$ 1,073
NEXUS Pipeline
Schedule of Equity Method Investments [Line Items]
Percent Owned	50.00%
Gas Storage and Pipelines
Schedule of Equity Method Investments [Line Items]
Investments	$ 1,685	1,585
Gas Storage and Pipelines | NEXUS Pipeline
Schedule of Equity Method Investments [Line Items]
Investments	$ 1,345	$ 1,260
Percent Owned	50.00%	50.00%
Gas Storage and Pipelines | Vector Pipeline
Schedule of Equity Method Investments [Line Items]
Investments	$ 131	$ 123
Percent Owned	40.00%	40.00%
Gas Storage and Pipelines | Millennium Pipeline
Schedule of Equity Method Investments [Line Items]
Investments	$ 209	$ 202
Percent Owned	26.00%	26.00%
Other Segments
Schedule of Equity Method Investments [Line Items]
Investments	$ 177	$ 186