| **Debt (Details) (USD $)**                                                                                                                                                                                                                                            | 3 Months Ended               | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------|-----------------|
||
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | $ 4,111,000,000              |                 | $ 4,123,000,000 |  |
| Unamortized Discount                                                                                                                                                                                                                                                  | (14,000,000)                 |                 | (15,000,000) |  |
| Total Debt, Net of Discount                                                                                                                                                                                                                                           | 4,097,000,000                |                 | 4,108,000,000 |  |
| Long-term Debt Due After One Year                                                                                                                                                                                                                                     | 3,723,000,000                |                 | 3,736,000,000 |  |
| Credit Facility due October 14, 2016 [Member]                                                                                                                                                                                                                         |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 0                            | [1]             | 0 | [1] |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 0.00%                        |                 | 0.00% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Oct. 14,         2016        |                 | Oct. 14,         2016 |  |
| Revolving Credit Facility Maximum Borrowing Capacity                                                                                                                                                                                                                  | 4,000,000,000                |                 |   |  |
| CONSOL Installment Payment, due September 30, 2013                                                                                                                                                                                                                    |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 328,000,000                  |                 | 328,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 1.79%                        | [2]             | 1.79% | [2] |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Sep. 30,         2013        |                 | Sep. 30,         2013 |  |
| Long-Term Debt and Capital Lease Obligations, Current, net of discount                                                                                                                                                                                                | (325,000,000)                |                 | (324,000,000) |  |
| FPSO Lease Obligation                                                                                                                                                                                                                                                 |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 299,000,000                  |                 | 311,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 0.00%                        |                 | 0.00% |  |
| Long-Term Debt and Capital Lease Obligations, Current, net of discount                                                                                                                                                                                                | (49,000,000)                 |                 | (48,000,000) |  |
| 5 1/4% Senior Notes, due April 15, 2014                                                                                                                                                                                                                               |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 200,000,000                  |                 | 200,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 5.25%                        |                 | 5.25% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Apr. 15,         2014        |                 | Apr. 15,         2014 |  |
| 8 1/4% Senior Notes, due March 1, 2019                                                                                                                                                                                                                                |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 1,000,000,000                |                 | 1,000,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 8.25%                        |                 | 8.25% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Mar.        01,         2019 |                 | Mar.        01,         2019 |  |
| 4.15% Senior Notes, due December 15, 2021                                                                                                                                                                                                                             |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 1,000,000,000                |                 | 1,000,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 4.15%                        |                 | 4.15% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Dec. 15,         2021        |                 | Dec. 15,         2021 |  |
| 7¼% Senior Notes, due October 15, 2023                                                                                                                                                                                                                           |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 100,000,000                  |                 | 100,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 7.25%                        |                 | 7.25% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Oct. 15,         2023        |                 | Oct. 15,         2023 |  |
| 8% Senior Notes, due April 1, 2027                                                                                                                                                                                                                                    |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 250,000,000                  |                 | 250,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 8.00%                        |                 | 8.00% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Apr.        01,         2027 |                 | Apr.        01,         2027 |  |
| 6% Senior Notes, due March 1, 2041                                                                                                                                                                                                                                    |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | 850,000,000                  |                 | 850,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 6.00%                        |                 | 6.00% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Mar.        01,         2041 |                 | Mar.        01,         2041 |  |
| 7 1/4% Senior Debentures, due August 1, 2097                                                                                                                                                                                                                          |                         |                 |   |  |
| **Debt Instrument [Line Items]**                                                                                                                                                                                                                                      |                         |                 |   |  |
| Debt                                                                                                                                                                                                                                                                  | $ 84,000,000                 |                 | $ 84,000,000 |  |
| Interest Rate (percentage in hundredths)                                                                                                                                                                                                                              | 7.25%                        |                 | 7.25% |  |
| Debt instrument, maturity date                                                                                                                                                                                                                                        | Aug.        01,         2097 |                 | Aug.        01,         2097 |  |
|                                                                                                                                                                                                                                                                       |
| [1]Our Credit Agreement provides for a $4.0 billion unsecured revolving Credit Facility. The Credit Facility is available for general corporate purposes.[2]Imputed rate based on the prevailing market rates for similar debt instruments at the date of assessment. |

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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Interest rate stated in the contractual debt agreement.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer plus capital lease obligations due to be paid more than one year after the balance sheet date.
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| - Definition
Obligation related to long-term debt (excluding convertible debt) and capital leases, the portion which is due in one year or less in the future.
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