Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities [Line Items]
Accrued liabilities	$ 498	$ 533
Revenue payable [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	196	164
Accrued capital costs [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	92	128
Accrued lease operating expenses [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	37	48
Employee incentive expense [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	48	53
Accrued interest on debt [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	67	66
Taxes payable [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	15	25
Other accrued liabilities [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	$ 43	$ 49