Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0.6	$ 1.1	$ 1.7	$ 3.2
Interest cost	3.5	2.6	10.5	7.7
Expected return on plan assets	(3.8)	(5.9)	(11.3)	(17.6)
Amortization of prior service costs	0.0	0.0	0.1	0.1
Amortization of net loss	1.7	0.9	4.9	2.6
Net periodic benefit cost (income)	2.0	(1.3)	5.9	(4.0)
Other postretirement benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.0	0.0	0.1	0.1
Interest cost	1.0	0.9	2.9	2.2
Amortization of prior service costs	0.0	(0.3)	0.0	(1.3)
Amortization of net loss	0.0	0.2	0.1	1.0
Curtailment gain, net	0.0	(8.0)	0.0	(8.0)
Net periodic benefit cost (income)	$ 1.0	$ (7.2)	$ 3.1	$ (6.0)