Foreign Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Foreign operations data
Revenues	$ 352.8	$ 359.6	$ 348.4	$ 316.1	$ 362.1	$ 362.9	$ 358.9	$ 334.4	$ 1,376.9	$ 1,418.3	$ 1,449.9
Identifiable assets	$ 7,422.4				7,105.4				$ 7,422.4	7,105.4	6,894.2
Foreign Operations (Textual) [Abstract]
Maximum percentage of consolidated revenues derive from any individual foreign country									10.00%
Percentage of company's identifiable assets	10.00%								10.00%
Foreign [Member]
Foreign operations data
Revenues									$ 324.0	320.7	329.4
Identifiable assets	$ 2,407.2				2,098.2				2,407.2	2,098.2	1,992.3
United States [Member]
Foreign operations data
Revenues									1,052.9	1,097.6	1,120.5
Identifiable assets	$ 5,015.2				$ 5,007.2				$ 5,015.2	$ 5,007.2	$ 4,901.9