Retirement Plans - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4.9	$ 5.5	$ 10.0	$ 11.1
Interest cost	2.2	1.6	4.5	3.1
Expected return on assets	(3.6)	(3.0)	(7.5)	(6.1)
Net loss	0.4	1.1	0.9	2.3
Prior service cost (credit)	0.1	0.2	0.3	0.4
Total benefit cost (credit)	4.0	5.4	8.2	10.8
Retiree Health Care Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost			0.1	0.1
Net loss	0.1	0.1	0.1	0.1
Prior service cost (credit)	(0.2)	(0.2)	(0.4)	(0.4)
Total benefit cost (credit)	$ (0.1)	$ (0.1)	$ (0.2)	$ (0.2)