ACQUISITIONS - Aggregate Purchase Price Paid for Acquisitions and Other Adjustments to Consideration (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Cash	$ 52.5	$ 63.9	$ 2,419.4
Adjustments to Prior Year Acquisitions
Business Acquisition [Line Items]
Cash	(0.4)
Promissory notes reduction resulting from adjustment	(0.4)
Contingent consideration	(9.6)
Total purchase price	(10.4)
Series of individual business acquisitions for Year 2016, 2015 and 2014
Business Acquisition [Line Items]
Cash	52.9	55.4	2,420.7
Promissory notes	25.3	40.9	64.1
Deferred consideration	1.1	4.1	3.2
Contingent consideration	0.1	1.0	10.1
Total purchase price	$ 79.4	$ 101.4	$ 2,498.1