Retirement Benefits - Schedule of Pension and Other Postretirement Benefits (Income) Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Benefits
Pension and Other Postretirement Benefits:
Service cost			$ 0.1	$ 0.1	$ 0.1
Interest cost			8.6	11.2	12.1
Expected return on plan assets			(6.9)	(7.5)	(7.5)
Amortization of prior service cost			0.3	0.0	0.0
Settlement	$ (10.0)		(10.0)	0.0	0.0
Curtailment		$ (0.7)	(0.7)	0.0	0.0
Recognition of actuarial gains			(0.1)	(0.1)	0.0
Net periodic benefit (income) cost			(8.7)	3.7	4.7
Other Postretirement Benefits
Pension and Other Postretirement Benefits:
Service cost			0.0	0.0
Interest cost			0.4	0.4	0.6
Recognition of actuarial gains			(0.4)	(1.3)	(2.0)
Net periodic benefit (income) cost			$ 0.0	$ (0.9)	$ (1.4)