Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leased Assets [Line Items]
2018	$ 91.8
2019	84.8
2020	69.8
2021	44.8
2022	36.7
Later years	93.5
Future Minimum Payments Due	421.4
Rent expense	106.0	$ 96.0	$ 92.5
Facilities
Operating Leased Assets [Line Items]
2018	55.6
2019	48.0
2020	40.3
2021	28.9
2022	25.0
Later years	93.4
Future Minimum Payments Due	291.2
Vehicles
Operating Leased Assets [Line Items]
2018	17.6
2019	17.3
2020	16.7
2021	12.1
2022	11.1
Later years	0.1
Future Minimum Payments Due	74.9
Other
Operating Leased Assets [Line Items]
2018	18.6
2019	19.5
2020	12.8
2021	3.8
2022	0.6
Later years	0.0
Future Minimum Payments Due	$ 55.3