Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Accumulated other comprehensive loss, net of tax
Foreign currency translation	$ (275.5)	$ (300.8)	$ (291.1)	$ (330.7)
Pension and other postretirement liability adjustment, net of deferred tax effect	(100.4)	(115.0)	(103.4)	(117.1)
Accumulated other comprehensive loss	(375.9)	(415.8)	(394.5)	$ (447.8)
Tax effect of pension liability adjustment	60.6		$ 61.6
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	4.1	3.5
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(1.1)	(1.4)
Other comprehensive income, before reclassification, foreign currency translation	15.6	29.9
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	0.0	0.0
Other comprehensive income, reclassification adjustment, foreign currency translation	0.0	0.0
Other comprehensive income, reclassification, pension	3.0	2.1
Translation adjustments	15.6	29.9
Pension and other postretirement liability adjustments, net of tax	3.0	2.1
Other comprehensive income (loss)	18.6	32.0
Before reclassification [Member]
Accumulated other comprehensive loss, net of tax
Other comprehensive income (loss)	15.6	29.9
Reclassified [Member]
Accumulated other comprehensive loss, net of tax
Other comprehensive income (loss)	$ 3.0	$ 2.1