v2.4.0.6

Assets and Liabilities with Recurring Fair Value Measurements (Tables) | 12 Months Ended
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Dec. 31, 2011
Fair Value Measurements [Abstract] |
Fair Value, Measurement Inputs, Disclosure | The following tables present our financial assets and liabilities that were accounted for at fair value on a recurring basis as of December 31, 2011 and 2010, by level within the fair value hierarchy. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect our estimate of the fair value of our assets and liabilities and their placement within the fair value hierarchy levels.
| Assets and Liabilities with Recurring Fair Value Measures as of December 31, 2011
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (in millions)
Assets: |  |  |  |  |  |  |
Cash equivalents(1) | $ | 1,415 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,415 |
Margin deposits | 140 |  |  | — |  |  | — |  |  | 140 |
Commodity instruments: |  |  |  |  |  |  |
Commodity futures contracts | 1,043 |  |  | — |  |  | — |  |  | 1,043 |
Commodity forward contracts(2) | — |  |  | 74 |  |  | 37 |  |  | 111 |
Interest rate swaps | — |  |  | 10 |  |  | — |  |  | 10 |
Total assets | $ | 2,598 |  |  | $ | 84 |  |  | $ | 37 |  |  | $ | 2,719 |
Liabilities: |  |  |  |  |  |  |
Margin deposits held by us posted by our counterparties | $ | 34 |  |  | $ | — |  |  | $ | — |  |  | $ | 34 |
Commodity instruments: |  |  |  |  |  |  |
Commodity futures contracts | 899 |  |  | — |  |  | — |  |  | 899 |
Commodity forward contracts(2) | — |  |  | 184 |  |  | 20 |  |  | 204 |
Interest rate swaps | — |  |  | 320 |  |  | — |  |  | 320 |
Total liabilities | $ | 933 |  |  | $ | 504 |  |  | $ | 20 |  |  | $ | 1,457 |
| Assets and Liabilities with Recurring Fair Value Measures as of December 31, 2010
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (in millions)
Assets: |  |  |  |  |  |  |
Cash equivalents(1) | $ | 1,297 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,297 |
Margin deposits | 162 |  |  | — |  |  | — |  |  | 162 |
Commodity instruments: |  |  |  |  |  |  |
Commodity futures contracts | 550 |  |  | — |  |  | — |  |  | 550 |
Commodity forward contracts(2) | — |  |  | 287 |  |  | 54 |  |  | 341 |
Interest rate swaps | — |  |  | 4 |  |  | — |  |  | 4 |
Total assets | $ | 2,009 |  |  | $ | 291 |  |  | $ | 54 |  |  | $ | 2,354 |
Liabilities: |  |  |  |  |  |  |
Margin deposits held by us posted by our counterparties | $ | 6 |  |  | $ | — |  |  | $ | — |  |  | $ | 6 |
Commodity instruments: |  |  |  |  |  |  |
Commodity futures contracts | 574 |  |  | — |  |  | — |  |  | 574 |
Commodity forward contracts(2) | — |  |  | 119 |  |  | 24 |  |  | 143 |
Interest rate swaps | — |  |  | 371 |  |  | — |  |  | 371 |
Total liabilities | $ | 580 |  |  | $ | 490 |  |  | $ | 24 |  |  | $ | 1,094 |
___________
(1) | As of December 31, 2011 and 2010, we had cash equivalents of $1,249 million and $1,094 million included in cash and cash equivalents and $166 million and $203 million included in restricted cash, respectively.
(2) | Includes OTC swaps and options.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation | The following table sets forth a reconciliation of changes in the fair value of our net derivative assets (liabilities) classified as level 3 in the fair value hierarchy for the years ended December 31, 2011, 2010 and 2009 (in millions):
| 2011 |  | 2010 |  | 2009
Balance, beginning of period | $ | 30 |  |  | $ | 38 |  |  | $ | 105 |
Realized and unrealized gains (losses): |  |  |  |  |
Included in net income: |  |  |  |  |
Included in operating revenues(1) | 5 |  |  | 7 |  |  | 14 |
Included in fuel and purchased energy expense(2) | — |  |  | — |  |  | 5 |
Included in OCI | 2 |  |  | 2 |  |  | (4 | )
Purchases, issuances and settlements: |  |  |  |  |
Settlements | (18 | ) |  | (20 | ) |  | (48 | )
Transfers in and/or out of level 3(3): |  |  |  |  |
Transfers into level 3(4) | (2 | ) |  | — |  |  | — |
Transfers out of level 3(5) | — |  |  | 3 |  |  | (34 | )
Balance, end of period | $ | 17 |  |  | $ | 30 |  |  | $ | 38 |
Change in unrealized gains relating to instruments still held at end of period(2) | $ | 5 |  |  | $ | 7 |  |  | $ | 19 |
___________
(1) | For power contracts and Heat Rate swaps and options, included on our Consolidated Statements of Operations.
(2) | For natural gas contracts, swaps and options, included on our Consolidated Statements of Operations.
(3) | We transfer amounts among levels of the fair value hierarchy as of the end of each period. There were no significant transfers into/out of level 1 during the years ended December 31, 2011, 2010 and 2009.
(4) | We had $2 million in losses transferred out of level 2 into level 3 for the year ended December 31, 2011, due to changes in market liquidity in various power and natural gas markets.There were no significant transfers into level 3 for the years ended December 31, 2010 and 2009.
(5) | There were no significant transfers out of level 3 for the year ended 2011. We had $3 million in losses and $(34) million in (gains) transferred out of level 3 into level 2 for the years ended December 31, 2010 and 2009, respectively, due to changes in market liquidity in various power markets.

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- Definition Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income, and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issuances, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19279-110258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258 + Details
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- Definition Tabular disclosure of the fair value measurement of assets and liabilities which includes [financial] instruments measured at fair value that are classified in stockholders' equity. Such assets and liabilities may be measured on a recurring or nonrecurring basis. The disclosures which may be required or desired include: (1) for assets and liabilities measured on a recurring basis, disclosure may include: (a) the fair value measurements at the reporting date; (b) the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets or liabilities (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3); (c) for fair value measurements using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (i) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (ii) purchases, sales, issuances, and settlements (net); (iii) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs); (d) the amount of the total gains or losses for the period in subparagraph (c) (i) above included in earnings (or changes in net assets) that are attributable to the change in unrealized gains or losses relating to those assets and liabilities still held at the reporting date and a description of where those unrealized gains or losses are reported in the statement of income (or activities); (e) the valuation technique(s) used to measure fair value and a discussion of changes in valuation techniques, if any, during the period and (2) for assets and liabilities that are measured at fair value on a nonrecurring basis (for example, impaired assets) disclosure may include, in addition to (a) above: (a) the reasons for the fair value measurements recorded; (b) the same as (b) above; (c) for fair value measurements using significant unobservable inputs (Level 3), a description of the inputs and the information used to develop the inputs; and (d) the valuation technique(s) used to measure fair value and a discussion of changes, if any, in the valuation technique(s) used to measure similar assets and/or liabilities in prior periods. Where the quoted price in an active market for the identical liability is not available, the Level 1 input is the quoted price of an identical liability when traded as an asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19279-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 33 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 107 -Paragraph 10 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19296-110258 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 6 -Footnote 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19190-110258 + Details
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