Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Pension Plans
Net Periodic Benefit Cost
Service cost	$ 2.4	$ 1.6
Interest cost	2.7	3.0
Expected return on assets	(2.6)	(2.9)
Other	0.6	0.3
Total benefit cost	3.1	2.0
Contributions to pension plans	1.4
Estimated employer contribution to pension plans during current fiscal year	4.2
Retiree Health Care Plan
Net Periodic Benefit Cost
Service cost	0.0	0.0
Interest cost	0.1	0.2
Expected return on assets	0.0	0.0
Other	(0.1)	(0.2)
Total benefit cost	0.0	$ 0.0
Contributions to retiree health care plan	$ 0.3