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Select Balance Sheet Information - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Property, Plant and Equipment [Line Items] |  |
Property, Plant and Equipment, net of accumulated depreciation | $ 2,289,491 | $ 2,212,717
Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 3,046,027 | 2,958,311
Less Accumulated Depreciation and Amortization | 876,330 | 859,988
Property, Plant and Equipment, net of accumulated depreciation | 2,169,697 | 2,098,323
Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 318,388 | 309,098
Less Accumulated Depreciation and Amortization | 198,594 | 194,704
Property, Plant and Equipment, net of accumulated depreciation | 119,794 | 114,394
Electric Plant in Service | Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 2,917,699 | 2,844,379
Construction Work in Progress | Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 128,328 | 113,932
Construction Work in Progress | Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 22,840 | 15,170
Nonelectric Property, Plant and Equipment in Service | Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | $ 295,548 | $ 293,928

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