Postretirement Benefit Plans (Debt Securities, Trading, and Equity Securities, FV-NI) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	$ 4.8	$ 4.8
Unrealized Gains	0.3	0.5
Unrealized Losses	(0.1)	0.0
Fair Value	5.0	5.3
Level 1 Securities:
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	4.6	4.6
Unrealized Gains	0.3	0.5
Unrealized Losses	(0.1)	0.0
Fair Value	4.8	5.1
Level 2 Securities:
Defined Benefit Plan Disclosure [Line Items]
Adjusted Cost	0.2	0.2
Unrealized Gains	0.0	0.0
Unrealized Losses	0.0	0.0
Fair Value	$ 0.2	$ 0.2