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Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Deferred Tax Assets |  |
Retirement Benefit Obligations | $ 6.1 | $ 11.2
Regulatory Assets & Liabilities | 0.0 | 8.9
Net Operating Loss Carryforwards | 2.3 | 0.1
Tax Credit Carryforwards | 2.0 | 1.3
Other, net | 2.5 | 1.3
Total Deferred Tax Assets | 18.5 | 13.9
Deferred Tax Liabilities |  |
Utility Plant Differences | 203.6 | 180.3
Regulatory Assets & Liabilities | 5.6 | 0.0
Other, net | 1.0 | 0.8
Total Deferred Tax Liabilities | 204.6 | 190.0
Net Deferred Tax Liabilities | $ 186.1 | $ 176.1

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