Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accrued Liabilities [Line Items]
Accrued liabilities	$ 879	$ 978
Revenue payable [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	182	175
Accrued capital costs [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	451	458
Accrued lease operating expenses [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	30	71
Employee incentive expense [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	65	64
Accrued interest on debt [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	73	72
Taxes payable [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	27	93
Other accrued liabilities [Member]
Accrued Liabilities [Line Items]
Accrued liabilities	$ 51	$ 45