v2.4.0.6

Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Restricted Cash and Cash Equivalents Items [Line Items] |  |  |
Prior Period Reclassification Adjustment |  | $ 10 | $ 9
Held-to-maturity Securities, Restricted | 25 | 25 |
Current | 193 | 139 |
Non-current | 60 | 55 |
Total | 253 | 194 |
Prior Period Adjustment [Abstract] |  |  |
Cash and cash equivalents subject to project finance facilities and lease agreements | 131 | 306 |
Inventory | 301 | 294 |
Property, plant and equipment, salvage value (as a percent) | 10.00% |  |
Property, plant and equipment, salvage value of rotables (as a percent) | 0.15% |  |
Impairment of long-lived assets held for use |  |  | 95
Impairment loss | 0 | 0 | 116
Asset retirement obligations | 38 | 27 |
Freestone Energy Center [Member] |  |  |
Jointly Owned Plants [Abstract] |  |  |
Jointly Owned Utility Plant, Proportionate Ownership Share | 75.00% |  |
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service | 392 |  |
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation | (124) |  |
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress | 1 |  |
Hidalgo Energy Center [Member] |  |  |
Jointly Owned Plants [Abstract] |  |  |
Jointly Owned Utility Plant, Proportionate Ownership Share | 78.50% |  |
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service | 252 |  |
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation | (86) |  |
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress | 0 |  |
Debt Service |  |  |
Restricted Cash and Cash Equivalents Items [Line Items] |  |  |
Current | 11 | 11 |
Non-current | 41 | 42 |
Total | 52 | 53 |
Construction Major Maintenance |  |  |
Restricted Cash and Cash Equivalents Items [Line Items] |  |  |
Current | 32 | 33 |
Non-current | 14 | 10 |
Total | 46 | 43 |
Security Project Insurance |  |  |
Restricted Cash and Cash Equivalents Items [Line Items] |  |  |
Current | 101 | 79 |
Non-current | 3 | 0 |
Total | 104 | 79 |
Other |  |  |
Restricted Cash and Cash Equivalents Items [Line Items] |  |  |
Current | 49 | 16 |
Non-current | 2 | 3 |
Total | 51 | 19 |
Greenfield [Member] |  |  |
Prior Period Adjustment [Abstract] |  |  |
Ownership percentage in equity method investment | 50.00% |  |
Whitby [Member] |  |  |
Prior Period Adjustment [Abstract] |  |  |
Ownership percentage in equity method investment | 50.00% |  |
Two Development Projects [Member] |  |  |
Prior Period Adjustment [Abstract] |  |  |
Impairment loss |  |  | $ 21

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- Definition Carrying amount (lower of cost or market) as of the balance sheet date of inventories less all valuation and other allowances. Excludes noncurrent inventory balances (expected to remain on hand past one year or one operating cycle, if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765 + Details
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- Definition The period end amount of construction work in progress at a jointly owned electricity generation plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The period end amount of accumulated depreciation in a jointly owned electricity generation plant. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.C) -URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section C + Details
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- Definition The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -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 Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230 + Details
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- Definition Stated as a percentage, the estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose) divided by its [historical] capitalized cost. + References No definition available. + Details
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