Reportable Segments Reportable Segments Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 2,919	$ 3,214	$ 8,585	$ 9,857
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(7)	(10)	(29)	(33)
Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenues	1,803	1,925	5,229	6,073
Natural Gas Pipelines | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(6)	(9)	(26)	(30)
Products Pipelines
Segment Reporting Information [Line Items]
Revenues	442	484	1,282	1,350
Terminals
Segment Reporting Information [Line Items]
Revenues	423	507	1,282	1,521
Terminals | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(1)	(1)	(3)	(3)
CO2
Segment Reporting Information [Line Items]
Revenues	$ 251	$ 298	$ 792	$ 913