Benefit Plans and Other Postretirement Benefits, Net pension expense (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Components of net pension expense:
Service cost	$ 1.0	$ 1.9
Interest cost	6.1	6.5
Expected return on plan assets	(7.2)	(7.3)
Amortization of prior service cost	0.3	0.4
Amortization of net actuarial losses	1.0	0.6
Net pension (income) expense	1.2	$ 2.1
United States
Defined Benefit Plan Disclosure
Estimated future employer contribution in fiscal year	$ 0.0