STOCK-BASED COMPENSATION AND EMPLOYEE BENEFIT PLANS (Employee Benefit Plans) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) employee	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Contribution Plan Disclosure [Line Items]
Number of active non-supervisory Canadian employees | employee	12
Net periodic benefit cost	$ 0.4	$ 0.4	$ 0.3
Pension assets measured at fair value	9.3	8.4
Projected benefit obligation	10.9	9.9
Level 1
Defined Contribution Plan Disclosure [Line Items]
Pension assets measured at fair value	3.9	3.5
Level 2
Defined Contribution Plan Disclosure [Line Items]
Pension assets measured at fair value	$ 5.4	$ 4.9