SEGMENT REPORTING - Reconciliation of Company's Primary Measure of Segment Profitability (EBITDA) to Income (Loss) from Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	$ 190.9	$ 212.3	$ 380.2	$ 411.8
Depreciation	(32.7)	(29.2)	(63.5)	(58.3)
Business Transformation	(21.8)		(43.9)
Intangible Amortization	(32.9)	(29.5)	(64.8)	(58.6)	$ (118.4)
Acquisition and Integration	(1.8)	(11.2)	(5.9)	(22.7)
Operational Optimization	(7.0)	(25.5)	(15.9)	(36.4)
Divestitures	(13.0)	(3.6)	(17.1)	(3.6)
Litigation, Settlements and Regulatory Compliance	(16.4)	(301.7)	(43.9)	(303.6)
Other	(2.9)	(3.9)	(8.7)	(6.4)
Income (loss) from operations	62.4	(192.3)	116.5	(77.8)
Domestic And Canada Regulated Waste And Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	196.8	213.4	386.8	417.1
Depreciation	(19.8)	(16.0)	(37.7)	(33.2)
Intangible Amortization	(24.2)	(21.9)	(47.4)	(43.6)
International Regulated Waste And Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	26.9	26.1	59.9	54.0
Depreciation	(7.4)	(7.8)	(14.7)	(15.6)
Intangible Amortization	(6.6)	(5.5)	(13.2)	(10.9)
All Other
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Adjusted EBITDA	(32.8)	(27.2)	(66.5)	(59.3)
Depreciation	(5.5)	(5.4)	(11.1)	(9.5)
Intangible Amortization	$ (2.1)	$ (2.1)	$ (4.2)	$ (4.1)