Segment Information (Details) (USD $) In Millions | 3 Months Ended | 9 Months Ended | |
|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Dec. 31, 2010 |
|---|
| Segment Information [Line Items] | | | | | |
| Oil and gas revenues | $ 628 | $ 449 | $ 1,794 | $ 1,355 | |
| Operating expenses: | | | | | |
| Lease operating | 115 | 86 | 333 | 237 | |
| Production and other taxes | 95 | 21 | 245 | 77 | |
| Depreciation, depletion and amortization | 189 | 156 | 528 | 463 | |
| General and administrative | 51 | 40 | 132 | 117 | |
| Total income tax provision (benefit) | 155 | 93 | 273 | 293 | |
| Other | 0 | 0 | 0 | 10 | |
| Total operating expenses | 450 | 303 | 1,238 | 904 | |
| Income (Loss) from operations | 178 | 146 | 556 | 451 | |
| Interest expenses, net of interest income, capitalized interest and other | (16) | (23) | (61) | (71) | |
| Commodity derivative income | 262 | 131 | 249 | 414 | |
| Income before income taxes | 424 | 254 | 744 | 794 | |
| Additions to long-lived assets | 691 | 390 | 2,114 | 1,412 | |
| Total assets | 8,903 | 7,226 | 8,903 | 7,226 | 7,494 |
Domestic [Member] | | | | | |
| Segment Information [Line Items] | | | | | |
| Oil and gas revenues | 444 | 357 | 1,313 | 1,055 | |
| Operating expenses: | | | | | |
| Lease operating | 93 | 68 | 260 | 195 | |
| Production and other taxes | 19 | 2 | 56 | 33 | |
| Depreciation, depletion and amortization | 154 | 128 | 440 | 371 | |
| General and administrative | 49 | 39 | 128 | 113 | |
| Total income tax provision (benefit) | 48 | 44 | 159 | 124 | |
| Other | 0 | 0 | 0 | 10 | |
| Additions to long-lived assets | 597 | 364 | 1,858 | 1,280 | |
| Total assets | 7,879 | 6,420 | 7,879 | 6,420 | |
| Net Income (Loss) From Oil And Gas Properties | 81 | 76 | 270 | 209 | |
Malaysia [Member] | | | | | |
| Segment Information [Line Items] | | | | | |
| Oil and gas revenues | 159 | 80 | 416 | 259 | |
| Operating expenses: | | | | | |
| Lease operating | 21 | 17 | 69 | 39 | |
| Production and other taxes | 71 | 17 | 173 | 38 | |
| Depreciation, depletion and amortization | 29 | 24 | 73 | 78 | |
| General and administrative | 1 | 1 | 3 | 3 | |
| Total income tax provision (benefit) | 14 | 8 | 37 | 39 | |
| Other | 0 | 0 | 0 | 0 | |
| Additions to long-lived assets | 81 | 18 | 208 | 99 | |
| Total assets | 789 | 604 | 789 | 604 | |
| Net Income (Loss) From Oil And Gas Properties | 23 | 13 | 61 | 62 | |
China [Member] | | | | | |
| Segment Information [Line Items] | | | | | |
| Oil and gas revenues | 25 | 12 | 65 | 41 | |
| Operating expenses: | | | | | |
| Lease operating | 1 | 1 | 4 | 3 | |
| Production and other taxes | 5 | 2 | 16 | 6 | |
| Depreciation, depletion and amortization | 6 | 4 | 15 | 11 | |
| General and administrative | 1 | 0 | 1 | 1 | |
| Total income tax provision (benefit) | 3 | 2 | 7 | 6 | |
| Other | 0 | 0 | 0 | 0 | |
| Additions to long-lived assets | 13 | 8 | 48 | 33 | |
| Total assets | 235 | 202 | 235 | 202 | |
| Net Income (Loss) From Oil And Gas Properties | 9 | 3 | 22 | 14 | |
Other International [Member] | | | | | |
| Segment Information [Line Items] | | | | | |
| Oil and gas revenues | 0 | 0 | 0 | 0 | |
| Operating expenses: | | | | | |
| Lease operating | 0 | 0 | 0 | 0 | |
| Production and other taxes | 0 | 0 | 0 | 0 | |
| Depreciation, depletion and amortization | 0 | 0 | 0 | 3 | |
| General and administrative | 0 | 0 | 0 | 0 | |
| Total income tax provision (benefit) | 0 | 0 | 0 | (1) | |
| Other | 0 | 0 | 0 | 0 | |
| Additions to long-lived assets | 0 | 0 | 0 | 0 | |
| Total assets | 0 | 0 | 0 | 0 | |
| Net Income (Loss) From Oil And Gas Properties | $ 0 | $ 0 | $ 0 | $ (2) | |