Benefit Plans and Other Postretirement Benefits, Net pension expense (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Components of net pension expense:
Service cost	$ 0.8	$ 1.8	$ 1.8	$ 3.7
Interest cost	6.0	6.5	12.0	13.0
Expected return on plan assets	(7.2)	(7.3)	(14.3)	(14.6)
Amortization of prior service cost	0.3	0.5	0.6	0.9
Amortization of net actuarial losses	0.7	0.5	1.7	1.1
Net pension (income) expense	0.6	$ 2.0	1.8	$ 4.1
United States
Defined Benefit Plan Disclosure
Estimated future employer contribution in fiscal year	$ 0.0		$ 0.0