Commitments and Contingencies Legal, Environmental or Regulatory (Details)		1 Months Ended	26 Months Ended	38 Months Ended
	May 16, 2016 employee count	May 31, 2015 bbl	Jun. 30, 2018 USD ($) count	Jun. 30, 2018 USD ($) count lawsuit	Dec. 31, 2017 USD ($)
Legal, Environmental or Regulatory Matters
Estimated undiscounted reserve for environmental liabilities			$ 138,000,000	$ 138,000,000	$ 162,000,000
Amounts probable of recovery under insurance and from third parties under indemnification agreements			49,000,000	49,000,000	55,000,000
Trade accounts receivable and other receivables, net
Legal, Environmental or Regulatory Matters
Amounts probable of recovery under insurance and from third parties under indemnification agreements			23,000,000	23,000,000	29,000,000
Other long-term assets, net
Legal, Environmental or Regulatory Matters
Amounts probable of recovery under insurance and from third parties under indemnification agreements			26,000,000	26,000,000	26,000,000
Accounts payable and accrued liabilities
Legal, Environmental or Regulatory Matters
Estimated undiscounted reserve for environmental liabilities, short-term			53,000,000	53,000,000	72,000,000
Other long-term liabilities and deferred credits
Legal, Environmental or Regulatory Matters
Estimated undiscounted reserve for environmental liabilities, long-term			85,000,000	85,000,000	$ 90,000,000
Line 901 Incident
Legal, Environmental or Regulatory Matters
Estimated undiscounted reserve for environmental liabilities			76,000,000	76,000,000
Amounts probable of recovery under insurance and from third parties under indemnification agreements			40,000,000	40,000,000
Estimated size of release (in bbl) | bbl		2,934
Estimated size of release to reach Pacific Ocean (in bbl) | bbl		598
Fines or penalties assessed			0	0
Aggregate total estimated costs			335,000,000	335,000,000
Recoveries from insurance carriers				180,000,000
Total release costs probable of recovery			220,000,000	220,000,000
Line 901 Incident | Trade accounts receivable and other receivables, net
Legal, Environmental or Regulatory Matters
Amounts probable of recovery under insurance and from third parties under indemnification agreements			16,000,000	16,000,000
Line 901 Incident | Accounts payable and accrued liabilities
Legal, Environmental or Regulatory Matters
Estimated undiscounted reserve for environmental liabilities, short-term			$ 44,000,000	$ 44,000,000
Line 901 Incident | May 2016 Indictment
Legal, Environmental or Regulatory Matters
Number of employees charged | employee	1
Total counts included in the indictment | count	46		15	15
Total number of counts dismissed | count			31
Number of felony charges dismissed | count			1
Number of misdemeanor charges relating to wildlife allegedly taken | count			9	9
Number of counts relating to the release of crude oil or reporting of the release | count			6	6
Number of felony charges relating to the release of crude oil or reporting of the release | count			3	3
Line 901 Incident | Class Action Lawsuits
Legal, Environmental or Regulatory Matters
Number of cases filed during the period | lawsuit				9
Number of cases consolidated into a single proceeding | lawsuit				6
Line 901 Incident | Securities Law Class Action Lawsuits
Legal, Environmental or Regulatory Matters
Number of cases filed during the period | lawsuit				2
Line 901 Incident | Unitholder Derivative Lawsuits
Legal, Environmental or Regulatory Matters
Number of cases filed during the period | lawsuit				4
UNITED STATES | Line 901 Incident | Unitholder Derivative Lawsuits
Legal, Environmental or Regulatory Matters
Number of lawsuits dismissed | lawsuit				2
TEXAS | Line 901 Incident | Unitholder Derivative Lawsuits
Legal, Environmental or Regulatory Matters
Number of lawsuits dismissed | lawsuit				1