SIGNIFICANT ACCOUNTING POLICIES - ACCRUED AND OTHER LIABILITIES (Details) - USD ($) $ in Millions	12 Months Ended			36 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Intangible assets
Impairment charges related to finite-lived intangible assets	$ 0.0	$ 0.0	$ 0.0
Impairment charges related to indefinite-lived intangible assets and goodwill for impairment	0.0	0.0	$ 0.0	$ 0.0
Accrued and other liabilities
Payroll and vacation related accruals	25.7	24.7		25.7
Employee incentives and other related accruals	19.5	17.4		19.5
Uninsured risks and related liabilities - short term	9.9	15.4		9.9
Deferred revenues	5.7	5.0		5.7
Interest on debt	5.1	5.4		5.1
Multi-employer withdrawal liability - short-term (see Note 12)	10.8	4.1		10.8
Pension and post-retirement liabilities - short term (see Note 11)	3.0	3.0		3.0
Other liabilities	2.2	5.4		2.2
Total	81.9	80.4		81.9
Other long-term liabilities
Pension and post-retirement liabilities (see Note 11)	79.4	75.1		79.4
Multi-employer withdrawal liabilitiy (see Note 12)	56.6	65.1		56.6
Uninsured risks and related liabilities	27.3	29.5		27.3
Other long-term liabilities	14.0	8.5		14.0
Total	$ 177.3	$ 178.2		$ 177.3
Customer Relationships. | Minimum
Intangible assets
Expected useful lives	3 years
Customer Relationships. | Maximum
Intangible assets
Expected useful lives	21 years