Related-Party Transactions Related-Party Transactions, Summary of Transactions Narrative (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2017	Sep. 30, 2016
Revenue from Related Parties	[1]	$ 219	$ 184	[2]	$ 624	$ 521	[2]
Related Party Transaction, Expenses from Transactions with Related Party	[3]	32	38		109	107
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party		$ 20	$ 19		$ 58	52
Concentration Risk, Percentage		49.00%	60.00%		49.00%
Cost of Reimbursable Expense		$ 7	$ 3		$ 12	12
Partner to Andeavor [Member] | Omnibus Agreement
Payment for Administrative Fees					11
Andeavor to Partner | Secondment and Logistics Services Agreement
Long-term Purchase Commitment, Amount		$ 6	$ 1		$ 16	$ 7

[1] Andeavor accounted for 49% and 60% of our total revenues for the three months ended September 30, 2017 and 2016, respectively, and 49% and 58% for the nine months ended September 30, 2017 and 2016, respectively.

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

[3] reimbursements from Andeavor 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 September 30, 2017 and 2016, respectively, and $12 million for both the nine months ended September 30, 2017 and 2016.