Related-Party Transactions Related-Party Transactions, Summary of Transactions Narrative (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018
Recovery of Direct Costs		$ 7		$ 3		$ 10	$ 10
Revenues		601		569	[1],[2]	1,231	1,115	[1],[2]
Related Party Transactions, Operating Expenses	[3]	113		72	[4]	217	134	[4]
Related Party Transactions, General and Administrative Expenses		$ 15		$ 22	[4]	$ 29	$ 46	[4]
Concentration Risk, Percentage		71.00%		68.00%		71.00%	64.00%
Payments of Distributions to Affiliates			$ 294
Secondment and Logistics Services Agreement
Term Of Agreement						10 years
Length Of Time For Continuing Minimum Payments						60 days
Partner to Andeavor | Omnibus Agreement
Payment for Administrative Fees						$ 17
Andeavor to Partner | Secondment and Logistics Services Agreement
Long-term Purchase Commitment, Amount		$ 24		$ 4		47	$ 10
Affiliated Entity
Revenues	[5]	$ 424		$ 389	[2],[4]	$ 868	$ 716	[2],[4]

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

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

[3] Excludes reimbursements from our Sponsor pursuant to the Amended Omnibus Agreement, the Carson Assets Indemnity Agreement and other affiliate agreements of $7 million and $3 million for the three months ended June 30, 2019 and 2018, respectively, and $10 million for both the six months ended June 30, 2019 and 2018.

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

[5] Represents 71% and 68% of our total revenues for the three months ended June 30, 2019 and 2018, respectively, and 71% and 64% of our total revenues for the six months ended June 30, 2019 and 2018, respectively.