Related-Party Transactions Related-Party Transactions, Summary of Transactions Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
Jun. 30, 2016 |
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| Revenue from Related Parties | [1] | $ 202 | $ 168 | [2] | $ 405 | $ 337 | [2] | ||||||
| Related Party Transaction, Expenses from Transactions with Related Party | [3] | 38 | 34 | 77 | 69 | ||||||||
| Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party | $ 18 | $ 16 | $ 38 | $ 33 | |||||||||
| Concentration Risk, Percentage | 49.00% | 57.00% | 49.00% | 57.00% | |||||||||
| Volume Gains (Losses) Value | $ 2 | $ 2 | $ 5 | $ 3 | |||||||||
| Cost of Reimbursable Expense | 3 | 3 | 5 | 9 | |||||||||
| Partner to Andeavor [Member] | Omnibus Agreement | |||||||||||||
| Payment for Administrative Fees | 11 | ||||||||||||
| Andeavor to Partner | Secondment and Logistics Services Agreement | |||||||||||||
| Long-term Purchase Commitment, Amount | $ 5 | $ 1 | $ 10 | $ 6 | |||||||||
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