Accrued Liabilities (Details) (USD $) In Millions | Sep. 30, 2011 | Dec. 31, 2010 |
|---|---|---|
| Accrued Liabilities | ||
| Total accrued liabilities | $ 747 | $ 670 |
Revenue payable [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 80 | 69 |
Accrued capital costs [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 369 | 327 |
Accrued lease operating expenses [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 75 | 54 |
Employee incentive expense [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 54 | 59 |
Accrued interest on debt [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 43 | 41 |
Taxes payable [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | 106 | 81 |
Other accrued liabilities [Member] | ||
| Accrued Liabilities | ||
| Total accrued liabilities | $ 20 | $ 39 |