Benefit Plans and Other Postretirement Benefits, Net pension expense (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Components of net pension expense:
Service cost	$ 1.5	$ 1.9
Interest cost	3.5	2.8
Expected return on plan assets	(7.5)	(7.8)
Amortization of prior service cost	0.4	0.5
Amortization of net actuarial losses	4.1	6.2
Net pension expense	2.0	$ 3.6
United States
Defined Benefit Plan Disclosure
Estimated future employer contribution in fiscal year	$ 0.0
Weighted average assumptions used to determine net periodic benefit cost/expense:
Expected long-term return on assets (as a percent)	5.50%