BUSINESS COMBINATIONS - Schedule of Adjustments Reflected in Pro Forma Net Income (Loss) and Net Income (Loss) Per Share Amounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Increase in intangible amortization expense	$ (5.8)	$ (6.4)	$ (18.4)	$ (17.9)
Decrease in income tax expense	(8.3)	(8.6)	(8.3)	(14.5)
2018 Acquisitions
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Increase in intangible amortization expense	$ (1.1)	(1.1)	$ (3.6)	(1.9)
2018 Acquisitions | Acquisition-related costs
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Increase in intangible amortization expense		0.2		(0.7)
Exclusion of buyer transaction costs		0.0		0.7
Decrease in income tax expense		$ 0.2		$ 0.2