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Postretirement Benefit Plans (Debt Securities, Trading, and Equity Securities, FV-NI) (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items] |  |
Adjusted Cost | $ 4.1 | $ 4.8
Unrealized Gains | 0.9 | 0.5
Unrealized Losses | 0.0 | 0.0
Fair Value | 5.0 | 5.3
Level 1 Securities: |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Adjusted Cost | 4.0 | 4.6
Unrealized Gains | 0.9 | 0.5
Unrealized Losses | 0.0 | 0.0
Fair Value | 4.9 | 5.1
Level 2 Securities: |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Adjusted Cost | 0.1 | 0.2
Unrealized Gains | 0.0 | 0.0
Unrealized Losses | 0.0 | 0.0
Fair Value | $ 0.1 | $ 0.2

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