SEGMENT REPORTING - Reconciliation of Company's Primary Measure of Segment Profitability (EBITDA) to Income from Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	$ 183.9	$ 206.2	$ 564.1	$ 618.0
Depreciation	(32.1)	(30.4)	(95.6)	(88.7)
Business Transformation	(21.0)	(4.2)	(64.9)	(4.2)
Intangible Amortization	(31.8)	(29.9)	(96.6)	(88.5)	$ (118.4)
Acquisition and Integration	(1.6)	(10.8)	(7.5)	(33.5)
Operational Optimization	(3.6)	(16.0)	(19.5)	(52.4)
Divestitures	(2.0)	(9.1)	(19.1)	(12.7)
Litigation, Settlements and Regulatory Compliance	(17.3)	(1.3)	(61.2)	(304.9)
Other	(6.2)	(10.9)	(14.9)	(17.3)
Income from operations	68.3	93.6	184.8	15.8
Domestic And Canada Regulated Waste And Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	196.6	202.6	583.4	619.7
Depreciation	(19.0)	(17.6)	(56.7)	(50.8)
Intangible Amortization	(23.7)	(22.0)	(71.1)	(65.6)
International Regulated Waste And Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	20.9	23.5	80.8	77.4
Depreciation	(6.7)	(7.8)	(21.4)	(23.4)
Intangible Amortization	(6.0)	(5.9)	(19.2)	(16.8)
All Other
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	(33.6)	(19.9)	(100.1)	(79.1)
Depreciation	(6.4)	(5.0)	(17.5)	(14.5)
Intangible Amortization	$ (2.1)	$ (2.0)	$ (6.3)	$ (6.1)