Retirement and Other Benefit Programs (Summary of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pensions | International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 9.5	$ 9.4	$ 28.5	$ 28.2
Interest cost	1.3	1.2	3.9	3.6
Expected return on plan assets	(2.0)	(1.8)	(6.0)	(5.4)
Amortization of net prior service cost	0.0	0.0	0.0	0.0
Amortization of actuarial (gain)/loss	(0.3)	0.4	(0.9)	1.3
Net periodic benefit cost	8.5	9.2	25.5	27.7
Pensions | United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.0	3.7	0.0	11.1
Interest cost	3.9	3.9	11.7	11.7
Expected return on plan assets	(4.3)	(4.0)	(12.9)	(12.0)
Amortization of net prior service cost	0.0	0.0	0.0	0.0
Amortization of actuarial (gain)/loss	0.0	0.0	0.0	0.0
Net periodic benefit cost	(0.4)	3.6	(1.2)	10.8
OPEB | United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.0	0.4	0.0	1.2
Interest cost	0.1	0.3	0.3	0.9
Expected return on plan assets	0.0	0.0	0.0	0.0
Amortization of net prior service cost	(0.2)	0.0	(0.6)	0.0
Amortization of actuarial (gain)/loss	0.0	0.0	0.0	0.0
Net periodic benefit cost	$ (0.1)	$ 0.7	$ (0.3)	$ 2.1