Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			$ 2,085.4
Other comprehensive income (loss) before reclassifications			2.1
Amounts reclassified from accumulated other comprehensive loss			4.9
Other comprehensive (loss) income	$ 11.6	$ 3.4	7.0	$ (19.0)
Ending equity	2,140.9		2,140.9
Cash flow hedge (loss) gain
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(0.7)
Other comprehensive income (loss) before reclassifications			(0.5)
Amounts reclassified from accumulated other comprehensive loss			0.8
Other comprehensive (loss) income			0.3
Ending equity	(0.4)		(0.4)
Unrealized gain (loss) on available-for- sale securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			1.0
Other comprehensive income (loss) before reclassifications			(0.1)
Amounts reclassified from accumulated other comprehensive loss			0.0
Other comprehensive (loss) income			(0.1)
Ending equity	0.9		0.9
Pension and post retirement benefit plan adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(212.0)
Other comprehensive income (loss) before reclassifications			0.0
Amounts reclassified from accumulated other comprehensive loss			4.1
Other comprehensive (loss) income			4.1
Ending equity	(207.9)		(207.9)
Cumulative translation adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(117.5)
Other comprehensive income (loss) before reclassifications			2.7
Amounts reclassified from accumulated other comprehensive loss			0.0
Other comprehensive (loss) income			2.7
Ending equity	(114.8)		(114.8)
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning equity			(329.2)
Ending equity	$ (322.2)		$ (322.2)