Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ 1,960.5
Other comprehensive income (loss) before Reclassifications	(8.5)	$ (17.8)	$ (23.0)
Amounts reclassified from accumulated other comprehensive loss	12.2	0.6	7.1
Other comprehensive income (loss)	3.7	(17.2)	(15.9)
End of period	2,085.4	1,960.5
Cash Flow Hedge (Loss) Gain
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(0.5)	0.8	(0.8)
Other comprehensive income (loss) before Reclassifications	0.4	(0.8)	1.9
Amounts reclassified from accumulated other comprehensive loss	(0.6)	(0.5)	(0.3)
Other comprehensive income (loss)	(0.2)	(1.3)	1.6
Reclassification of stranded tax effects		0.0
End of period	(0.7)	(0.5)	0.8
Unrealized Gain (Loss) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	0.6	(2.0)	(0.6)
Other comprehensive income (loss) before Reclassifications	0.4	0.8	(1.4)
Amounts reclassified from accumulated other comprehensive loss	0.0	1.8	0.0
Other comprehensive income (loss)	0.4	2.6	(1.4)
Reclassification of stranded tax effects		0.0
End of period	1.0	0.6	(2.0)
Pension and Post Retirement Benefit Plan Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(203.2)	(158.7)	(176.5)
Other comprehensive income (loss) before Reclassifications	(21.6)	(21.5)	10.4
Amounts reclassified from accumulated other comprehensive loss	12.8	7.0	7.4
Other comprehensive income (loss)	(8.8)	(14.5)	17.8
Reclassification of stranded tax effects		(30.0)
End of period	(212.0)	(203.2)	(158.7)
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(129.8)	(125.8)	(91.9)
Other comprehensive income (loss) before Reclassifications	12.3	3.7	(33.9)
Amounts reclassified from accumulated other comprehensive loss	0.0	(7.7)	0.0
Other comprehensive income (loss)	12.3	(4.0)	(33.9)
Reclassification of stranded tax effects		0.0
End of period	(117.5)	(129.8)	(125.8)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(332.9)	(285.7)	(269.8)
Other comprehensive income (loss)	3.7	(17.2)	(15.9)
Reclassification of stranded tax effects		(30.0)
End of period	$ (329.2)	$ (332.9)	$ (285.7)