SEGMENT REPORTING - Financial Information Concerning Company's Reportable Segments (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 Information [Line Items]
Revenues		$ 917.7		$ 1,810.1
Gross Profit	$ 353.3	381.7	$ 711.8	750.4
Depreciation	32.7	29.2	63.5	58.3
Intangible amortization	32.9	29.5	64.8	58.6	$ 118.4
Adjusted EBITDA	190.9	212.3	380.2	411.8
Revenues	883.3		1,778.3
Domestic And Canada Regulated Waste And Compliance Services
Segment Reporting Information [Line Items]
Revenues		649.1		1,282.8
Gross Profit	264.2	284.9	524.7	563.0
Depreciation	19.8	16.0	37.7	33.2
Intangible amortization	24.2	21.9	47.4	43.6
Adjusted EBITDA	196.8	213.4	386.8	417.1
Revenues	644.5		1,283.0
International Regulated Waste And Compliance Services
Segment Reporting Information [Line Items]
Revenues		180.0		361.6
Gross Profit	57.0	56.5	119.8	115.0
Depreciation	7.4	7.8	14.7	15.6
Intangible amortization	6.6	5.5	13.2	10.9
Adjusted EBITDA	26.9	26.1	59.9	54.0
Revenues	171.6		351.9
Other
Segment Reporting Information [Line Items]
Revenues		88.6		165.7
Gross Profit	32.1	40.3	67.3	72.4
Depreciation	5.5	5.4	11.1	9.5
Intangible amortization	2.1	2.1	4.2	4.1
Adjusted EBITDA	(32.8)	$ (27.2)	(66.5)	$ (59.3)
Revenues	$ 67.2		$ 143.4