Pension Plans (Components of Net Periodic Pension Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Defined Benefit Plan, Type [Extensible List]	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember
Interest cost	$ 18.3	$ 21.3	$ 19.8
Expected return on plan assets	(22.2)	(23.4)	(20.6)
Recognized net actuarial loss	5.8	11.3	9.6
Net periodic pension cost	$ 1.9	$ 9.2	$ 8.8