Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accrued Liabilities
Accrued liabilities	$ 978	$ 801
Revenue payable [Member]
Accrued Liabilities
Accrued liabilities	175	95
Accrued capital costs [Member]
Accrued Liabilities
Accrued liabilities	458	355
Accrued lease operating expenses [Member]
Accrued Liabilities
Accrued liabilities	71	95
Employee incentive expense [Member]
Accrued Liabilities
Accrued liabilities	51	50
Accrued interest on debt [Member]
Accrued Liabilities
Accrued liabilities	72	43
Taxes payable [Member]
Accrued Liabilities
Accrued liabilities	93	108
Other accrued liabilities [Member]
Accrued Liabilities
Accrued liabilities	$ 58	$ 55