Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance, beginning of period	$ 1,606.3	$ 1,490.2	$ 1,573.2	$ 1,445.1	$ 1,369.5	$ 1,396.3	$ 1,573.2	$ 1,396.3
Other comprehensive income (loss) before reclassifications							(8.6)
Amounts reclassified out from accumulated other comprehensive income (loss)							(1.3)
Other comprehensive income (loss), net of tax	28.3	4.5	(42.7)	(18.2)	1.2	0.8	(9.9)	(16.2)
Balance, end of period	1,718.9	1,606.3	1,490.2	1,487.6	1,445.1	1,369.5	1,718.9	1,487.6
(Losses) gains on derivatives
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance, beginning of period			(0.8)				(0.8)
Other comprehensive income (loss) before reclassifications							2.5
Amounts reclassified out from accumulated other comprehensive income (loss)							(3.5)
Other comprehensive income (loss), net of tax							(1.0)
Balance, end of period	(1.8)						(1.8)
Change in equity affiliate investment AOCI
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance, beginning of period			0.4				0.4
Other comprehensive income (loss) before reclassifications							0.0
Amounts reclassified out from accumulated other comprehensive income (loss)							0.0
Other comprehensive income (loss), net of tax							0.0
Balance, end of period	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]
Balance, beginning of period			(40.3)				(40.3)
Other comprehensive income (loss) before reclassifications							(6.2)
Amounts reclassified out from accumulated other comprehensive income (loss)							2.2
Other comprehensive income (loss), net of tax							(4.0)
Balance, end of period	(44.3)						(44.3)
Foreign currency translation
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance, beginning of period			(108.9)				(108.9)
Other comprehensive income (loss) before reclassifications							(4.9)
Amounts reclassified out from accumulated other comprehensive income (loss)							0.0
Other comprehensive income (loss), net of tax							(4.9)
Balance, end of period	(113.8)						(113.8)
Accumulated other comprehensive loss
Changes in the Components of Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance, beginning of period	(187.8)	(192.3)	(149.6)	(152.2)	(153.4)	(154.2)	(149.6)	(154.2)
Other comprehensive income (loss), net of tax	28.3	4.5	(42.7)	(18.2)	1.2	0.8
Balance, end of period	$ (159.5)	$ (187.8)	$ (192.3)	$ (170.4)	$ (152.2)	$ (153.4)	$ (159.5)	$ (170.4)