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Summary of Significant Accounting Policies Revenues (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Property, Plant and Equipment [Line Items] |  |
Pre-commercial Ops - capitalized revenue | $ 0 | $ (3)
Paradise CT Units 5-7 |  |
Property, Plant and Equipment [Line Items] |  |
Pre-commercial Ops - capitalized revenue |  | 3
Pre-commercial Ops - Capitalized Fuel |  | $ 3
Johnsonville Aeroderivative CT Units 25-28 |  |
Property, Plant and Equipment [Line Items] |  |
Pre-commercial Ops - capitalized revenue | 1 |
Pre-commercial Ops - Capitalized Fuel | $ 1 |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A + Details
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