Postretirement Benefits (Debt Securities, Trading, and Equity Securities, FV-NI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	$ 4.8	$ 5.5
Unrealized Gains	0.5	0.2
Unrealized Losses	0.0	(0.1)
Fair Value	5.3	5.6
Level 1 Securities:
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	4.6	5.1
Unrealized Gains	0.5	0.2
Unrealized Losses	0.0	(0.1)
Fair Value	5.1	5.2
Level 2 Securities:
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	0.2	0.4
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	$ 0.2	$ 0.4