Accumulated Other Comprehensive Loss - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ 1,798.9	$ 1,798.9
Other comprehensive income (loss) before Reclassifications		(17.8)	$ (23.0)	$ 24.4
Amounts reclassified from accumulated other comprehensive loss		0.6	7.1	8.3
Other comprehensive income (loss)		(17.2)	(15.9)	32.7
Reclassification of stranded tax effects	30.0	(30.0)
End of period		1,960.5	1,798.9
Cash Flow Hedge (Loss) Gain
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	0.8	0.8	(0.8)	0.0
Other comprehensive income (loss) before Reclassifications		(0.8)	1.9	(1.7)
Amounts reclassified from accumulated other comprehensive loss		(0.5)	(0.3)	0.9
Other comprehensive income (loss)		(1.3)	1.6	(0.8)
Reclassification of stranded tax effects		0.0
End of period		(0.5)	0.8	(0.8)
Unrealized Gain (Loss) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(2.0)	(2.0)	(0.6)	(1.2)
Other comprehensive income (loss) before Reclassifications		0.8	(1.4)	0.6
Amounts reclassified from accumulated other comprehensive loss		1.8	0.0	0.0
Other comprehensive income (loss)		2.6	(1.4)	0.6
Reclassification of stranded tax effects		0.0
End of period		0.6	(2.0)	(0.6)
Pension and Post Retirement Benefit Plan Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(158.7)	(158.7)	(176.5)	(180.5)
Other comprehensive income (loss) before Reclassifications		(21.5)	10.4	(3.4)
Amounts reclassified from accumulated other comprehensive loss		7.0	7.4	7.4
Other comprehensive income (loss)		(14.5)	17.8	4.0
Reclassification of stranded tax effects		(30.0)
End of period		(203.2)	(158.7)	(176.5)
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	(125.8)	(125.8)	(91.9)	(120.8)
Other comprehensive income (loss) before Reclassifications		3.7	(33.9)	28.9
Amounts reclassified from accumulated other comprehensive loss		(7.7)	0.0	0.0
Other comprehensive income (loss)		(4.0)	(33.9)	28.9
Reclassification of stranded tax effects		0.0
End of period		(129.8)	(125.8)	(91.9)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning of period	$ (285.7)	(285.7)	(269.8)	(302.5)
Other comprehensive income (loss)		(17.2)	(15.9)	32.7
Reclassification of stranded tax effects		(30.0)
End of period		$ (332.9)	$ (285.7)	$ (269.8)