Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.5	$ 2.8
Interest cost	3.1	3.0
Expected return on assets	(2.3)	(2.8)
Other	0.5	0.4
Total benefit cost (credit)	3.8	3.4
Contributions to pension plans	1.5
Estimated employer contribution to pension plans during current fiscal year	7.9
Retiree Health Care Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.0
Interest cost	0.1	0.1
Expected return on assets	0.0	0.0
Other	(0.2)	(0.2)
Total benefit cost (credit)	(0.1)	$ (0.1)
Contributions to retiree health care plan	$ 0.3