Property, Plant and Equipment - Classification of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 13,387	$ 14,504
Accumulated depreciation	(5,341)	(5,693)
Property, plant and equipment, net	8,046	8,811
Gathering and transmission systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 7,659	8,406
Gathering and transmission systems | Minimum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	20 years
Gathering and transmission systems | Maximum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	50 years
Processing, storage and terminal facilities
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 4,948	5,305
Processing, storage and terminal facilities | Minimum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	35 years
Processing, storage and terminal facilities | Maximum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	60 years
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 583	585
Other | Minimum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	3 years
Other | Maximum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	30 years
Finance lease assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 25	25
Finance lease assets [Member] | Minimum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	3 years
Finance lease assets [Member] | Maximum
Property, Plant and Equipment [Line Items]
Depreciable life of property, plant and equipment	6 years
Construction work in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 172	$ 183