Employee Benefits (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Retirement Benefits, Description [Abstract]
Number of participants domestic pension plan	3,500
Number of participants postretirement benefit plan	1,700
Deferred Compensation Arrangements [Abstract]
Deferred compensation liability	$ 96.2	$ 92.4
Deferred compensation expense	11.2	9.7	$ 6.3
Deferred benefit liability	117.0	129.1
Deferred benefit expense	7.3	8.8	$ 9.7
Cash surrender value of life insurance	177.4	171.5
Deferred compensation plan assets	15.9	12.9
Long-Term Disability Plan [Abstract]
Long-term disability plan obligation	8.4	$ 8.2
Long term disability plan, income replacement benefit obligation	$ 0.0