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Operations and Significant Accounting Policies - Supplemental Statement of Cash Flows Information (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |
Cash Paid During the Period for Interest – Net of Amounts Capitalized | $ 75.1 | $ 80.5 | $ 72.8
Cash Paid for Income Taxes | 19.1 | 19.5 | 6.0
Noncash Investing and Financing Activities |  |  |
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment | 15.5 | 2.2 | (9.6)
Reclassification of Property, Plant and Equipment to Inventory | 0.0 | 0.0 | 99.7
Capitalized Asset Retirement Costs | 55.0 | 5.8 | 11.8
AFUDC–Equity | $ 5.0 | $ 3.6 | $ 2.7

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