Operating Revenues (Revenues Disaggregated) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	$ 265	$ 270	$ 773	$ 835
Pipelines
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	117	121	325	347
Terminals
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	36	41	112	120
Storage, processing and other revenues
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	$ 112	$ 108	$ 336	$ 368