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Select Balance Sheet Information - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Property, Plant and Equipment [Line Items] |  |
Property, Plant and Equipment, net of accumulated depreciation | $ 2,709,311 | $ 2,692,460
Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 3,442,403 | 3,412,833
Less Accumulated Depreciation and Amortization | 911,470 | 899,049
Property, Plant and Equipment, net of accumulated depreciation | 2,530,933 | 2,513,784
Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 408,410 | 403,101
Less Accumulated Depreciation and Amortization | 230,032 | 224,425
Property, Plant and Equipment, net of accumulated depreciation | 178,378 | 178,676
Electric Plant in Service | Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 3,214,984 | 3,180,943
Construction Work in Progress | Electric Plant |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 227,419 | 231,890
Construction Work in Progress | Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | 15,830 | 40,536
Nonelectric Property, Plant and Equipment in Service | Nonelectric Property, Plant and Equipment |  |
Property, Plant and Equipment [Line Items] |  |
Property, plant and equipment, gross | $ 392,580 | $ 362,565

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