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Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Deferred Tax Assets |  |
Retirement Benefit Obligations | $ 11.2 | $ 11.0
Net Operating Loss Carryforwards | 0.1 | 3.5
Tax Credit Carryforwards | 1.3 | 1.0
Other, net | 1.3 | 1.4
Total Deferred Tax Assets | 13.9 | 16.9
Deferred Tax Liabilities |  |
Utility Plant Differences | 180.3 | 168.3
Regulatory Assets & Liabilities | 8.9 | 11.3
Other, net | 0.8 | 0.7
Total Deferred Tax Liabilities | 190.0 | 180.3
Net Deferred Tax Liabilities | $ 176.1 | $ 163.4

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