v2.4.0.6

Assets and Liabilities with Recurring Fair Value Measurements (Tables) | 12 Months Ended
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Dec. 31, 2012
Fair Value Measurements [Abstract] |
Fair Value Inputs, Assets, Quantitative Information [Table Text Block] | The following table presents quantitative information for the unobservable inputs used in our most significant level 3 fair value measurements at December 31, 2012:
|  | Quantitative Information about Level 3 Fair Value Measurements
|  | December 31, 2012
|  | Fair Value, Net Asset |  |  |  | Significant Unobservable |  |
|  | (Liability) |  | Valuation Technique |  | Input |  | Range
|  | (in millions) |  |  |  |  |  |
Physical Power |  | $ | 11 |  |  | Discounted cash flow |  | Market price (per MWh) |  | $23.75 — $53.82/MWh
Fair Value, Measurement Inputs, Disclosure | 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. The following tables present our financial assets and liabilities that were accounted for at fair value on a recurring basis as of December 31, 2012 and 2011, by level within the fair value hierarchy:
| Assets and Liabilities with Recurring Fair Value Measures as of December 31, 2012
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (in millions)
Assets: |  |  |  |  |  |  |
Cash equivalents(1) | $ | 1,502 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,502 |
Margin deposits | 196 |  |  | — |  |  | — |  |  | 196 |
Commodity instruments: |  |  |  |  |  |  |
Commodity exchange traded futures and swaps contracts | 385 |  |  | — |  |  | — |  |  | 385 |
Commodity forward contracts(2) | — |  |  | 24 |  |  | 24 |  |  | 48 |
Interest rate swaps | — |  |  | 4 |  |  | — |  |  | 4 |
Total assets | $ | 2,083 |  |  | $ | 28 |  |  | $ | 24 |  |  | $ | 2,135 |
Liabilities: |  |  |  |  |  |  |
Margin deposits held by us posted by our counterparties | $ | 11 |  |  | $ | — |  |  | $ | — |  |  | $ | 11 |
Commodity instruments: |  |  |  |  |  |  |
Commodity exchange traded futures and swaps contracts | 424 |  |  | — |  |  | — |  |  | 424 |
Commodity forward contracts(2) | — |  |  | 18 |  |  | 8 |  |  | 26 |
Interest rate swaps | — |  |  | 200 |  |  | — |  |  | 200 |
Total liabilities | $ | 435 |  |  | $ | 218 |  |  | $ | 8 |  |  | $ | 661 |
| 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 exchange traded futures and swaps 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 exchange traded futures and swaps contracts | 899 |  |  | — |  |  | — |  |  | 899 |
Commodity forward contracts(2) | — |  |  | 184 |  |  | 20 |  |  | 204 |
Interest rate swaps | — |  |  | 320 |  |  | — |  |  | 320 |
Total liabilities | $ | 933 |  |  | $ | 504 |  |  | $ | 20 |  |  | $ | 1,457 |
___________
(1) | As of December 31, 2012 and 2011, we had cash equivalents of $1,274 million and $1,249 million included in cash and cash equivalents and $228 million and $166 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, 2012, 2011 and 2010 (in millions):
| 2012 |  | 2011 |  | 2010
Balance, beginning of period | $ | 17 |  |  | $ | 30 |  |  | $ | 38 |
Realized and unrealized gains (losses): |  |  |  |  |
Included in net income: |  |  |  |  |
Included in operating revenues(1) | 8 |  |  | 5 |  |  | 7 |
Included in fuel and purchased energy expense(2) | — |  |  | — |  |  | — |
Included in OCI | — |  |  | 2 |  |  | 2 |
Purchases, issuances and settlements: |  |  |  |  |
Purchases | 3 |  |  | — |  |  | — |
Issuances | (1 | ) |  | — |  |  | — |
Settlements | (11 | ) |  | (18 | ) |  | (20 | )
Transfers in and/or out of level 3(3): |  |  |  |  |
Transfers into level 3(4) | — |  |  | (2 | ) |  | — |
Transfers out of level 3(5) | — |  |  | — |  |  | 3 |
Balance, end of period | $ | 16 |  |  | $ | 17 |  |  | $ | 30 |
Change in unrealized gains relating to instruments still held at end of period | $ | 8 |  |  | $ | 5 |  |  | $ | 7 |
___________
(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, 2012, 2011 and 2010.
(4) | There were no significant transfers into level 3 for the years ended December 31, 2012 and 2010. 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.
(5) | We had no significant transfers out of level 3 for the years ended December 31, 2012 and 2011. There were $3 million in losses transferred out of level 3 into level 2 for the year ended December 31, 2010 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 (loss), 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, issues, 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 Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 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=7578670&loc=d3e19279-110258 Reference 3: 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. + Details
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- Definition Tabular disclosure of quantitative information about the inputs used in the fair value measurement of assets. This disclosure may include, but is not limited to, the fair value of the asset, valuation technique used to measure fair value, the inputs used to measure fair value, the ranges of the inputs, and the weighted averages of the inputs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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- Definition The entire disclosure of the fair value measurement of assets and liabilities, which includes financial instruments measured at fair value that are classified in shareholders' equity, which may be measured on a recurring or nonrecurring basis. + 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=7578670&loc=d3e19279-110258 Reference 2: 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=7578670&loc=d3e19190-110258 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 Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 Reference 5: 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 6: 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 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. + Details
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