Related-Party Transactions Related-Party Transactions, Summary of Transactions Narrative (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 6 Months Ended | 9 Months Ended | |||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Nov. 14, 2017 |
Oct. 18, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
[4] | Mar. 31, 2017 |
[4] | Dec. 31, 2016 |
Jun. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
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| Cash Dividends Paid to Parent Company | $ 223 | |||||||||||||||||||||||||||
| Revenue from Related Parties | [1] | 934 | $ 521 | [2] | ||||||||||||||||||||||||
| Related Party Transaction, Expenses from Transactions with Related Party | [3] | 132 | 107 | |||||||||||||||||||||||||
| Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party | $ 62 | 52 | ||||||||||||||||||||||||||
| Concentration Risk, Percentage | 58.00% | 44.00% | ||||||||||||||||||||||||||
| Cost of Reimbursable Expense | $ 12 | 12 | ||||||||||||||||||||||||||
| Distribution Made to Limited Partner, Distributions Declared, Per Unit | $ 0.9852 | [4],[5] | $ 0.9710 | $ 0.9400 | $ 0.9100 | |||||||||||||||||||||||
| Distribution Made to Limited Partner, Distribution Date | Nov. 14, 2017 | [4],[5] | Aug. 14, 2017 | May 15, 2017 | Feb. 14, 2017 | |||||||||||||||||||||||
| Partner to Andeavor [Member] | Omnibus Agreement | ||||||||||||||||||||||||||||
| Payment for Administrative Fees | 11 | |||||||||||||||||||||||||||
| Andeavor to Partner | Secondment and Logistics Services Agreement | ||||||||||||||||||||||||||||
| Long-term Purchase Commitment, Amount | 16 | $ 7 | ||||||||||||||||||||||||||
| Western Refining Logistics | ||||||||||||||||||||||||||||
| Cash Dividends Paid to Parent Company | $ 19 | |||||||||||||||||||||||||||
| Distribution Made to Limited Partner, Distributions Declared, Per Unit | [6],[7] | $ 0.4675 | ||||||||||||||||||||||||||
| Subsequent Event | ||||||||||||||||||||||||||||
| Distribution Made to Limited Partner, Declaration Date | Oct. 18, 2017 | |||||||||||||||||||||||||||
| Subsequent Event | Western Refining Logistics | ||||||||||||||||||||||||||||
| Distribution Made to Limited Partner, Declaration Date | Jul. 25, 2017 | |||||||||||||||||||||||||||
| Distribution Made to Limited Partner, Distribution Date | Aug. 18, 2017 | |||||||||||||||||||||||||||
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