Business Segments - Segment Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Segment long-term assets	$ 12,230	$ 13,047
Current assets	958	1,080
Total assets	13,188	14,127
Operating Segments | Logistics and Marketing
Segment Reporting, Asset Reconciling Item [Line Items]
Segment long-term assets	3,861	3,848
Operating Segments | Gathering and Processing
Segment Reporting, Asset Reconciling Item [Line Items]
Segment long-term assets	8,101	8,904
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Segment long-term assets	$ 268	$ 295