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Debt and Financing Arrangements - Summary of Interest Expense and Interest Income (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Interest Expense |  |  |
Long-Term Debt | $ 27.8 | $ 24.7 | $ 24.7
Short-Term Debt | 8.4 | 9.2 | 3.0
Regulatory Liabilities | 1.5 | 1.0 | 0.6
Subtotal Interest Expense | 37.7 | 34.9 | 28.3
Interest Income |  |  |
Interest and Other Income | (8.4) | (6.2) | (2.8)
Interest Expense, Net | 29.3 | 28.7 | 25.5
Regulatory Assets |  |  |
Interest Income |  |  |
Interest and Other Income | (4.1) | (3.3) | (1.0)
AFUDC and Other |  |  |
Interest Income |  |  |
Interest and Other Income | $ (4.3) | $ (2.9) | $ (1.8)

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- Definition The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business). + References No definition available. + Details
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- Definition Aggregate amount of interest paid or due on all long-term debt. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph a -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph b -Subparagraph (1) -Publisher SEC Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(8)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 + Details
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- Definition The aggregate interest expense incurred on short-term borrowings including commercial paper and Federal funds purchased and securities sold under agreements to repurchase. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph a -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1402 -Paragraph b -Subparagraph (1) -Publisher SEC Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 + Details
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