Benefit Plans - Changes in Projected Benefit Obligation, Fair Value of Plan Assets and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in plan assets:
Balance	$ 29.4
Balance	32.3	$ 29.4
Pension benefits
Change in benefit obligation:
Balance	(55.5)	(269.8)
Service cost	(1.1)	(1.5)	$ (1.6)
Interest cost	(2.4)	(4.2)	(6.2)
Participants’ contributions	(0.2)	(0.4)
Actuarial gain (loss)	0.7	33.0
Benefits paid	2.5	6.9
Settlement loss	0.5	174.4
Foreign currency translation	(2.0)	6.1
Balance	(57.5)	(55.5)	(269.8)
Change in plan assets:
Balance	29.4	249.2
Actual return on plan assets	2.4	(42.4)
Employer contribution	1.1	8.4
Participants’ contributions	0.2	0.4
Benefits paid	(1.8)	(7.2)
Settlement loss	(0.5)	(174.4)
Foreign currency translation	1.5	(4.6)
Balance	32.3	29.4	249.2
Funded status at end of year	(25.2)	(26.1)
Other retirement benefits
Change in benefit obligation:
Balance	(3.9)	(5.6)
Service cost	0.0	0.0	0.0
Interest cost	(0.2)	(0.2)	(0.2)
Participants’ contributions	(0.4)	(0.4)
Actuarial gain (loss)	0.5	2.0
Benefits paid	0.3	0.3
Settlement loss	0.0	0.0
Foreign currency translation	0.0	0.0
Balance	(3.7)	(3.9)	(5.6)
Change in plan assets:
Balance	0.0	0.0
Actual return on plan assets	0.0	0.0
Employer contribution	(0.1)	(0.1)
Participants’ contributions	0.4	0.4
Benefits paid	(0.3)	(0.3)
Settlement loss	0.0	0.0
Foreign currency translation	0.0	0.0
Balance	0.0	0.0	$ 0.0
Funded status at end of year	$ (3.7)	$ (3.9)