Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	$ 1,573.2	$ 1,396.3	$ 1,279.9
Other comprehensive income (loss) before reclassifications	40.6	8.4
Amounts reclassified out	(1.6)	(3.8)
Other comprehensive income (loss), net of tax	39.0	4.6	(36.9)
Ending balance	1,854.5	1,573.2	1,396.3
(Losses) gains on derivatives
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	(0.8)	(0.4)
Other comprehensive income (loss) before reclassifications	2.8	5.4
Amounts reclassified out	(3.9)	(5.8)
Other comprehensive income (loss), net of tax	(1.1)	(0.4)
Ending balance	(1.9)	(0.8)	(0.4)
Change in equity affiliate investment AOCI
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	0.4	0.4
Other comprehensive income (loss) before reclassifications	0.2	0.0
Amounts reclassified out	0.0	0.0
Other comprehensive income (loss), net of tax	0.2	0.0
Ending balance	0.6	0.4	0.4
Defined benefit pension and other postretirement plans
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	(40.3)	(40.4)
Other comprehensive income (loss) before reclassifications	(2.5)	(1.9)
Amounts reclassified out	2.3	2.0
Other comprehensive income (loss), net of tax	(0.2)	0.1
Ending balance	(40.5)	(40.3)	(40.4)
Foreign currency translation
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	(108.9)	(113.8)
Other comprehensive income (loss) before reclassifications	40.1	4.9
Amounts reclassified out	0.0	0.0
Other comprehensive income (loss), net of tax	40.1	4.9
Ending balance	(68.8)	(108.9)	(113.8)
Total
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Beginning balance	(149.6)	(154.2)	(117.3)
Ending balance	$ (110.6)	$ (149.6)	$ (154.2)