ACCUMULATED OTHER COMPREHENSIVE INCOME, NET (Loss) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax
Beginning balance	$ 3,327.0	$ 3,285.4	$ 3,241.0	$ 3,149.6	$ 3,175.2	$ 3,110.6	$ 3,241.0
Other comprehensive income	(17.2)	(18.1)	14.7	(8.4)	(41.3)	24.8
Ending balance	3,328.7	3,327.0	3,285.4	3,151.9	3,149.6	3,175.2	3,328.7
Accumulated Other Comprehensive Income, net
AOCI Attributable to Parent, Net of Tax
Beginning balance	8.1	26.2	11.5	34.2	75.5	50.7	11.5
Other comprehensive income	(17.2)	(18.1)	14.7	(8.4)	(41.3)	24.8	(20.6)
Ending balance	(9.1)	$ 8.1	26.2	$ 25.8	$ 34.2	$ 75.5	(9.1)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax
Beginning balance			12.1				12.1
Other comprehensive income							(20.6)
Ending balance	(8.5)						(8.5)
Unrealized Investment Gain/Loss
AOCI Attributable to Parent, Net of Tax
Beginning balance			0.2				0.2
Ending balance	0.2						0.2
Post-Retirement Benefits
AOCI Attributable to Parent, Net of Tax
Beginning balance			$ (0.8)				(0.8)
Ending balance	$ (0.8)						$ (0.8)