Employee Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Periodic Benefit Cost
Interest cost	$ (17.3)	$ (18.1)
Pension Benefits [Member]
Net Periodic Benefit Cost
Interest cost	(17.3)	(18.1)	$ (26.9)
Expected return on plan assets	27.7	30.2	34.9
Net periodic benefit income	10.4	12.1	8.0
Settlement charge	(0.8)	(7.0)	0.0
Total income	$ 9.6	$ 5.1	$ 8.0