Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Cumulative foreign currency translation	$ (190.8)	$ (200.2)
Unrecognized pension costs (net of tax benefit of $64.6 in 2020 and $30.5 in 2019)	(114.9)	(96.1)
Unrealized gain (loss) on cash flow hedges (net of tax (benefit) expense of $(3.1) in 2020 and $0.3 in 2019)	(2.6)	5.9
Total accumulated other comprehensive income (loss)	(308.3)	(290.4)
Unrecognized pension costs, tax benefit	64.6	30.5
Unrealized gain (loss) on cash flow hedges, tax expense	(3.1)	0.3
Foreign currency translation adjustment [Abstract]
Foreign currency translation adjustment, pre-tax amount	10.9	(29.9)	$ (67.9)
Foreign currency translation adjustment, tax (expense) benefit	0.0	0.0	0.0
Foreign currency translation adjustments, net-of-tax amount	10.9	(29.9)	(67.9)
Pension plans [Abstract]
Net actuarial gains (losses) and prior service costs arising during the period, pre-tax amount	(37.9)	(30.6)	9.6
Net actuarial gains (losses) and prior service costs arising during the period, tax (expense) benefit	9.2	7.4	(1.8)
Net actuarial gains (losses) and prior service costs arising during the period, net-of-tax amount	(28.7)	(23.2)	7.8
Amortization of net actuarial (gains) losses and prior service costs, pre-tax amount	13.4	9.4	12.1
Amortization of net actuarial (gains) losses and prior service costs, tax (expense) benefit	(3.4)	(2.3)	(3.0)
Amortization of net actuarial (gains) losses and prior service costs, net-of-tax amount	10.0	7.1	9.1
Unrealized gains (losses) on cash flow hedges [Abstract]
Unrealized gains (losses) on cash flow hedges, pre-tax amount	(11.6)	0.3	1.5
Unrealized gains (losses) on cash flow hedges, tax (expense) benefit	3.1	(0.1)	0.1
Unrealized gains (losses) on cash flow hedges, net-of-tax amount	(8.5)	0.2	1.6
Total other comprehensive income (loss), pre-tax amount	(25.2)	(50.8)	(44.7)
Total other comprehensive income (loss), tax	8.9	5.0	(4.7)
Total other comprehensive income (loss), net of tax	$ (16.3)	$ (45.8)	$ (49.4)