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Operations and Significant Accounting Policies - Other Income (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Other Income |  |
Total Other Income | $ 8.6 | $ 4.1
Pension and Other Postretirement Benefit Plan Non-Service Credits |  |
Other Income |  |
Total Other Income | 4.3 | 2.0
Interest and Investment Income |  |
Other Income |  |
Total Other Income | 1.9 | 1.1
AFUDC - Equity |  |
Other Income |  |
Total Other Income | 1.2 | 0.5
Other |  |
Other Income |  |
Total Other Income | $ 1.2 | $ 0.5

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- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2 + Details
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