Benefit Plans Benefit Plans - Accumulated Benefit Obligation In Excess of Plan Assets (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	1.47%	1.16%
Projected benefit obligation	$ 452.0	$ 546.9
Accumulated benefit obligation	439.5	538.2
Fair value of plan assets	$ 359.5	$ 482.9
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.24%	4.62%
Projected benefit obligation	$ 569.0	$ 554.5
Accumulated benefit obligation	569.0	554.5
Fair value of plan assets	$ 378.7	$ 351.7