GOODWILL AND OTHER INTANGIBLE ASSETS - Carrying Values of Other Intangible Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets By Major Class [Line Items]
Gross Carrying Amount	$ 2,195.9	$ 2,184.0
Accumulated Amortization	424.7	392.5
Net Value	1,771.2	1,791.5	$ 1,862.0
Operating permits
Intangible Assets By Major Class [Line Items]
Carrying Amount, Indefinite Lived Intangible Assets	222.3	222.3
Tradenames
Intangible Assets By Major Class [Line Items]
Carrying Amount, Indefinite Lived Intangible Assets	318.2	317.4
Customer relationships
Intangible Assets By Major Class [Line Items]
Gross Carrying Amount	1,625.4	1,613.4
Accumulated Amortization	413.0	381.4
Net Value	1,212.4	1,232.0
Covenants not-to-compete
Intangible Assets By Major Class [Line Items]
Gross Carrying Amount	7.9	7.9
Accumulated Amortization	6.2	5.9
Net Value	1.7	2.0
Tradenames
Intangible Assets By Major Class [Line Items]
Gross Carrying Amount	6.0	6.0
Accumulated Amortization	2.0	1.8
Net Value	4.0	4.2
Other
Intangible Assets By Major Class [Line Items]
Gross Carrying Amount	16.1	17.0
Accumulated Amortization	3.5	3.4
Net Value	$ 12.6	$ 13.6