EQUITY-BASED COMPENSATION - Performance share units (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item					1	1
Grant date fair value of PSUs | $			$ 4.4		$ 7.0	$ 5.9
Compensation expense | $	$ (0.7)	$ 0.8	(2.2)	$ 1.7
Fair value of outstanding shares | $			$ 3.3
Weighted-average remaining life			1 year 9 months 18 days
Performance share units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item			0
Percentage of Target PSUs Earned	0.00%		0.00%
Performance share units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item			1.75
Percentage of Target PSUs Earned			175.00%
Return on assets Less than 9.6% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned			0.00%
Return on assets 9.6% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned			50.00%
Return on assets 12% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned			100.00%
Return on assets 14.4% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned			175.00%
Peer Group Outside of Top 10 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			0.00%
Peer Group Top 10 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			50.00%
Peer Group Top 7 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			100.00%
Peer Group Top 3 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			175.00%
Adjusted FCF Performance Percentage Less than 70% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			0.00%
Adjusted FCF Performance Percentage 70% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			50.00%
Adjusted FCF Performance Percentage 100% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			100.00%
Adjusted FCF Performance Percentage 130% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			175.00%
Return On Assets Five Percent [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned			5.00%