Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Curtailment	$ 0.0	$ 2.1	$ 0.0
Settlement effects	0.0	0.0	(50.4)
Net periodic benefit cost	7.3
Pension Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Service cost	10.4	10.2	10.6
Interest cost	9.8	10.5	13.8
Expected return on assets	(13.5)	(12.6)	(19.5)
Amortization of prior service credit	(1.3)	(1.4)	(1.3)
Amortization of transition obligation	0.0	0.1	0.1
Amortization of actuarial loss (gain)	4.9	4.8	5.9
Curtailment	0.0	2.1	0.0
Settlement effects	0.0	0.0	(50.4)
Net periodic benefit cost	10.3	9.5	60.0
Other changes in plan assets and benefit obligations recognized in OCI, pre-tax:
Net (gain) loss arising during period	(9.0)	19.2	17.7
Prior service credit arising during period	0.0	0.0	(0.7)
Amortization of prior service credit	1.3	1.4	1.3
Amortization of transition obligation	0.0	(0.1)	(0.1)
Amortization of actuarial (loss) gain	(4.9)	(4.8)	(5.9)
Curtailment	0.0	3.1	0.0
Settlement effects	0.0	0.0	50.4
Foreign currency translation	2.6	(3.2)	(1.6)
Total recognized in OCI	(10.0)	9.4	(39.7)
Total recognized in net periodic benefit cost and OCI	0.3	18.9	20.3
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.5	0.5
Interest cost	0.3	0.5	0.4
Expected return on assets	0.0	0.0	0.0
Amortization of prior service credit	(0.7)	0.0	0.0
Amortization of transition obligation	0.0	0.0	0.0
Amortization of actuarial loss (gain)	(2.6)	(1.4)	(1.4)
Curtailment	0.0	0.0	0.0
Settlement effects	0.0	0.0	0.0
Net periodic benefit cost	(3.0)	(0.4)	(0.5)
Other changes in plan assets and benefit obligations recognized in OCI, pre-tax:
Net (gain) loss arising during period	(1.1)	(0.1)	(0.8)
Prior service credit arising during period	0.0	(3.0)	0.0
Amortization of prior service credit	0.7	0.0	0.0
Amortization of transition obligation	0.0	0.0	0.0
Amortization of actuarial (loss) gain	2.6	1.4	1.4
Curtailment	0.0	0.0	0.0
Settlement effects	0.0	0.0	0.0
Foreign currency translation	0.0	0.0	0.0
Total recognized in OCI	2.2	(1.7)	0.6
Total recognized in net periodic benefit cost and OCI	(0.8)	(2.1)	0.1
Domestic Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	7.3	7.1	57.4
Domestic Plan [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	(3.0)	(0.4)	(0.5)
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	3.0	2.4	2.6
Foreign Plan [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Period Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 0.0	$ 0.0	$ 0.0