STOCK BASED COMPENSATION - Stock-Based Compensation Expense Resulting from Stock Option Awards, RSUs, PSUs and ESPP (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 6.7	$ 5.4	$ 19.5	$ 17.3
Stock Options | Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	2.5	3.7	8.4	11.6
Restricted Stock Units (RSUs) | Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	2.0	1.2	5.8	4.1
Performance-Based Restricted Stock Units | Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1.9	0.2	4.5	0.6
Employee Stock Purchase Plan | Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 0.3	$ 0.3	$ 0.8	$ 1.0