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Commitments and Contingencies - Ownership and Operating Interest Percentage (Details) - Colstrip [Member] | Mar. 31, 2023 | Jan. 16, 2023 | Sep. 30, 2022
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Avista [Member] | Unit 3 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 15.00% |  |
Avista [Member] | Unit 4 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 15.00% |  |
PacifiCorp [Member] | Unit 3 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 10.00% |  |
PacifiCorp [Member] | Unit 4 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 10.00% |  |
PGE [Member] | Unit 3 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 20.00% |  |
PGE [Member] | Unit 4 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 20.00% |  |
PSE [Member] | Unit 3 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 25.00% |  |
PSE [Member] | Unit 4 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 25.00% |  | 25.00%
NorthWestern [Member] | Unit 4 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 30.00% | 15.00% |
Talen [Member] | Unit 3 [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Owners percentage interest | 30.00% |  |

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- Definition The proportionate share of interest (percent) in a jointly owned utility plant. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 10.C) -URI https://asc.fasb.org/extlink&oid=122136288&loc=d3e659983-123033 + Details
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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 No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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