Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			$ 1,960.5		$ 1,960.5
Other comprehensive income (loss) before reclassifications					(32.8)
Amounts reclassified from accumulated other comprehensive loss					9.4
Other comprehensive (loss) income	$ (4.4)	$ (16.0)			(23.4)	$ (10.0)
Ending equity	2,031.0				2,031.0
Cash flow hedge (loss) gain
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(0.5)		(0.5)
Other comprehensive income (loss) before reclassifications					1.2
Amounts reclassified from accumulated other comprehensive loss					(0.7)
Other comprehensive (loss) income					0.5
Ending equity	0.0				0.0
Unrealized gain (loss) on available-for- sale securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			0.6		0.6
Other comprehensive income (loss) before reclassifications					0.5
Amounts reclassified from accumulated other comprehensive loss					0.0
Other comprehensive (loss) income					0.5
Ending equity	1.1				1.1
Defined benefit pension and post-retirement benefit items:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(203.2)		(203.2)
Other comprehensive income (loss) before reclassifications					(22.3)
Amounts reclassified from accumulated other comprehensive loss					10.1
Other comprehensive (loss) income					(12.2)
Ending equity	(215.4)				(215.4)
Cumulative translation adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(129.8)		(129.8)
Other comprehensive income (loss) before reclassifications					(12.2)
Amounts reclassified from accumulated other comprehensive loss					0.0
Other comprehensive (loss) income					(12.2)
Ending equity	(142.0)				(142.0)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity	(351.9)	(309.7)	(332.9)	$ (285.7)	(332.9)	(285.7)
Other comprehensive (loss) income	(4.4)	(16.0)	(19.0)	6.0
Ending equity	$ (356.3)	$ (325.7)	$ (351.9)	$ (309.7)	$ (356.3)	$ (325.7)