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Use of Collateral (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Use of Collateral [Abstract] |  |  |  |
Margin deposits | $ 140 | [1] | $ 162 | [1]
Natural gas and power prepayments | 42 |  | 43 |
Total margin deposits and natural gas and power prepayments with our counterparties | 182 | [2] | 205 | [2]
Letters of credit issued | 581 | [3] | 588 | [3]
First priority liens under power and natural gas agreements | 1 | [4] | 0 | [4]
First priority liens under interest rate swap agreements | 318 |  | 391 |
Total letters of credit and first priority liens with our counterparties | 900 |  | 979 |
Margin deposits held by us posted by our counterparties | 34 | [1],[5] | 6 | [1],[5]
Letters of credit posted with us by our counterparties | 0 |  | 66 |
Total margin deposits and letters of credit posted with us by our counterparties | 34 |  | 72 |
Use of Collateral (Textuals) [Abstract] |  |  |  |
Margin And Prepayment Amounts Included In Other Assets | 20 |  | 22 |
Margin And Prepayment Amounts Included In Margin Deposits And Other Prepaid Expenses | 162 |  | 183 |
Back-stopped amount of letters of credit used for commodity procurement and risk management activities |  |  | 63 |
Commodity Instruments Collateralized By First Priority Liens, Fair Value |  |  | $ 193 |
[1] | Balances are subject to master netting arrangements and presented on a gross basis on our Consolidated Balance Sheets. We do not offset fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement for financial statement presentation.
[2] | At December 31, 2011 and 2010, $162 million and $183 million, respectively, were included in margin deposits and other prepaid expense and $20 million and $22 million were included in other assets at December 31, 2011 and 2010, respectively, on our Consolidated Balance Sheets.
[3] | When we entered into our Corporate Revolving Facility on December 10, 2010, the letters of credit issued under our First Lien Credit Facility were either replaced by letters of credit issued under the Corporate Revolving Facility or back-stopped by an irrevocable standby letter of credit issued by a third party. Our letters of credit issued under our Corporate Revolving Facility used for our commodity procurement and risk management activities as of December 31, 2010 include those that were back-stopped of approximately $63 million. The back-stopped letters of credit were returned and extinguished during the first quarter of 2011.
[4] | At December 31, 2010, the fair value of our commodity derivative instruments collateralized by first priority liens was an asset of $193 million; therefore, there was no collateral exposure at December 31, 2010.
[5] | Included in other current liabilities on our Consolidated Balance Sheets.

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- Definition Derivative Collateral Obligation To Return Cash And Letters Of Credit Posted By Counterparties + References No definition available. + Details
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- Definition Derivative Collateral Right To Reclaim Cash And Natural Gas And Power Prepayments Total + References No definition available. + Details
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- Definition First priority liens under interest rate swap agreements + References No definition available. + Details
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- Definition First priority liens under power and natural gas agreements + References No definition available. + Details
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- Definition Letters of credit issued + References No definition available. + Details
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- Definition Letters of Credit Issued and First Priority Liens Under Power Natural Gas And Interest Rate Swap Agreements + References No definition available. + Details
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- Definition Letters Of Credit Posted By Counterparties + References No definition available. + Details
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- Definition Margin And Prepayment Amounts Included In Margin Deposits And Other Prepaid Expenses + References No definition available. + Details
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- Definition Natural gas and power prepayments + References No definition available. + Details
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- Details
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- Definition The amount of the obligation to return cash collateral under master netting arrangements that have not been offset against net derivative instrument positions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6935481&loc=d3e41678-113959 -Subparagraph (b) + Details
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- Definition The amount of the right to reclaim cash collateral under master netting arrangements that have not been offset against net derivative instrument positions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6935481&loc=d3e41678-113959 -Subparagraph (b) + Details
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