Pension Plans (Components of Net Periodic Pension (Benefit) Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Benefit Plan, Type [Extensible List]	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember	us-gaap:PensionPlansDefinedBenefitMember
Interest cost	$ 3.7	$ 4.6	$ 7.4	$ 9.2
Expected return on plan assets	(4.6)	(5.5)	(9.2)	(11.1)
Recognized net actuarial loss	0.8	1.4	1.6	2.9
Net periodic pension (benefit) cost	$ (0.1)	$ 0.5	$ (0.2)	$ 1.0