Segment Information - Assets by Segment (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and cash equivalents		$ 68	$ 5
Total assets		22,779	19,500
Equity method investments		4,174	4,010
Operating Segments | Logistics and Storage [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	6,566	4,611
Equity method investments		1,120	1,150
Operating Segments | Gathering and Processing [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	16,145	14,884
Equity method investments		$ 3,050	$ 2,860

[1] Equity method investments included in L&S assets were $1.12 billion at December 31, 2018 and $1.15 billion at December 31, 2017. Equity method investments included in G&P assets were $3.05 billion at December 31, 2018 and $2.86 billion at December 31, 2017.