Property, Plant and Equipment - Components of Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Land	$ 11		$ 11
Building and improvements	40		40
Pipeline and equipment	1,245		1,228
Other	33		33
Property, plant and equipment, gross	1,329		1,312
Accumulated depreciation and amortization	(626)		(613)
Property plant and equipment excluding construction in progress	703		699
Construction in progress	14		27
Property, plant and equipment, net	717		726
Operating lease, accumulated depreciation	136		133
Finance lease, accumulated depreciation	7		6
Depreciation and amortization expense	$ 13	$ 12
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	$ 369		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