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Selected Balance Sheet Information: Materials, Supplies, and Fuel Schedule (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023
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Selected Balance Sheet Information [Abstract] |  |
Materials and supplies | $ 103.9 | $ 105.9
Fuel - Electric Utilities | 7.6 | 7.7
Natural gas in storage | 43.9 | 47.3
Total materials, supplies and fuel | $ 155.4 | $ 160.9

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