Pension and Savings Plans - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of net periodic pension costs
Net periodic pension cost (benefit)	$ (38.3)	$ (1.8)	$ 19.4
Pension Plan
Components of net periodic pension costs
Service cost for benefits earned	0.2	0.3	2.0
Interest cost on projected benefit obligation	20.4	28.0	33.5
Expected return on plan assets	(22.9)	(29.7)	(31.4)
Settlement	0.0	(2.7)	0.0
Net actuarial (gain) loss	12.7	(25.6)	(16.6)
Net periodic pension cost (benefit)	$ 10.4	$ (29.7)	$ (12.5)