Property, Plant and Equipment - Components of Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Land	$ 12		$ 12		$ 11
Building and improvements	47		47		40
Pipeline and equipment	1,258		1,258		1,228
Other	34		34		33
Property, plant and equipment, gross	1,351		1,351		1,312
Accumulated depreciation and amortization	(652)		(652)		(613)
Property plant and equipment excluding construction in progress	699		699		699
Construction in progress	9		9		27
Property, plant and equipment, net	708		708		726
Operating lease, accumulated depreciation	143		143		133
Finance lease, accumulated depreciation	7		7		6
Depreciation and amortization expense	$ 13	$ 12	$ 39	$ 36
Building and Improvements | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			10 years
Building and Improvements | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			40 years
Pipeline and Equipment
Property Plant And Equipment [Line Items]
Operating lease cost			$ 372		369
Finance lease cost			$ 23		$ 23
Pipeline and Equipment | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			10 years
Pipeline and Equipment | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			30 years
Other | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			5 years
Other | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, depreciable life			25 years