Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Cumulative foreign currency translation	$ (104.1)	$ (147.3)
Unrecognized pension costs (net of tax benefit of $30.7 in 2017 and $39.4 in 2016)	(86.5)	(78.0)
Unrealized gain (loss) on cash flow hedges (net of tax expense of $0.7 in 2017 and $1.8 in 2016)	4.5	4.2
Total accumulated other comprehensive income (loss)	(186.1)	(221.1)
Unrecognized pension costs, tax benefit	30.7	39.4
Unrealized gain (loss) on cash flow hedges, tax expense	0.7	1.8
Foreign currency translation adjustment [Abstract]
Foreign currency translation adjustment, pre-tax amount	44.7	(40.2)	$ (76.6)
Foreign currency translation adjustment, tax (expense) benefit	0.0	0.0	0.0
Foreign currency translation adjustments, net-of-tax amount	44.7	(40.2)	(76.6)
Pension plans [Abstract]
Net actuarial gains (losses) and prior service costs arising during the period, pre-tax amount	(17.6)	(12.5)	0.5
Net actuarial gains (losses) and prior service costs arising during the period, tax (expense) benefit	4.4	4.1	0.5
Net actuarial gains (losses) and prior service costs arising during the period, net-of-tax amount	(13.2)	(8.4)	1.0
Amortization of net actuarial (gains) losses and prior service costs, pre-tax amount	7.6	8.0	9.6
Amortization of net actuarial (gains) losses and prior service costs, tax (expense) benefit	(2.9)	(2.8)	(3.3)
Amortization of net actuarial (gains) losses and prior service costs, net-of-tax amount	4.7	5.2	6.3
Unrealized gains (losses) on cash flow hedges [Abstract]
Unrealized gains (losses) on cash flow hedges, pre-tax amount	0.2	2.4	0.0
Unrealized gains (losses) on cash flow hedges, tax (expense) benefit	0.1	(0.8)	0.0
Unrealized gains (losses) on cash flow hedges, net-of-tax amount	0.3	1.6	0.0
Total other comprehensive income (loss), pre-tax amount	34.9	(42.3)	(66.5)
Total other comprehensive income (loss)	1.6	0.5	(2.8)
Total other comprehensive income (loss), net of tax	$ 36.5	$ (41.8)	$ (69.3)