REVENUES - Contract Liability (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Change in contract liability
Contract liability as of beginning of period	$ 76.7	$ 67.7
Revenue recognized: Amounts included in the contract liability at the beginning of the period	(76.7)	(67.7)
Increases due to invoices issued, excluding amounts recognized as revenues during the period	73.5	72.2
Business combination	0.5	3.0
Contract liability as of end of period	$ 74.0	$ 75.2