Operating Segments Operating Segments, Identifiable Assets (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	[1]	Dec. 31, 2015	[1]
Property, Plant and Equipment
Assets		$ 5,839	$ 5,860
Cash and cash equivalents		20	688	$ 682		$ 16
Gathering and Processing
Property, Plant and Equipment
Assets		4,035	3,392
Terminalling and Transportation
Property, Plant and Equipment
Assets		1,778	1,768
Corporate and Other [Member]
Property, Plant and Equipment
Assets	[2]	$ 26	700
North Dakota Gathering and Processing Assets [Member]
Property, Plant and Equipment
Cash and cash equivalents			$ 673

[1] (a)Adjusted to include the historical results of the Predecessors. See Note 1 for further discussion.

[2] Other consists mainly of $688 million in cash and cash equivalents as of December 31, 2016, of which $673 million was used to fund the acquisition of the North Dakota Gathering and Processing Assets on January 1, 2017, increasing the Gathering and Processing segment’s identifiable assets as of June 30, 2017.