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Operations and Significant Accounting Policies - Supplemental Statement of Cash Flows Information (Details) - USD ($) $ in Millions | 9 Months Ended
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Sep. 30, 2023 | Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |
Cash Paid for Interest – Net of Amounts Capitalized | $ 64.8 | $ 60.5
Cash Paid for Income Taxes – Net | 14.1 | 1.1
Noncash Investing and Financing Activities |  |
Increase in Accounts Payable for Capital Additions to Property, Plant and Equipment | 11.8 | 2.4
Reclassification of Property, Plant and Equipment to Inventory | 0.0 | 99.8
Capitalized Asset Retirement Costs | 2.4 | 9.0
AFUDC–Equity | $ 2.5 | $ 2.4

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