ACCRUED LIABILITIES AND OTHER LONG TERM LIABILITIES - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued compensation	$ 80.0	$ 52.0
Accrued self-insurance	72.8	77.9
Accrued taxes	42.3	41.2
Accrued interest	14.7	13.6
Accrued small quantity medical waste customer class action legal settlement	0.0	295.0
Accrued professional services liabilities	40.1	34.3
Accrued disposal and landfill liabilities	15.9	13.2
Accrued liabilities – other	75.0	60.9
Total accrued liabilities	$ 340.8	$ 588.1