Employee Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Periodic Benefit Cost
Interest cost	$ (17.5)	$ (16.0)
Net pension income	6.0	12.4	$ 9.6
Pension Benefits
Net Periodic Benefit Cost
Interest cost	(17.5)	(16.0)	(17.3)
Expected return on plan assets	23.5	28.4	27.7
Net periodic benefit income	6.0	12.4	10.4
Settlement charge	0.0	0.0	(0.8)
Net pension income	$ 6.0	$ 12.4	$ 9.6