EQUITY COMPENSATION (Restricted Units) (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 31, 2018	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2018
Restricted units
Equity compensation
Units granted (in units)		2,000,000		4,457,869
Distribution equivalents made to holders			$ 4.5	$ 16.9
Units
Balance at the beginning of the period (in units)				13,751,888
Granted (in units)		2,000,000		4,457,869
Vested (in units)				(1,917,705)
Forfeited (in units)				(291,439)
Balance at the end of the period (in units)			16,000,613	16,000,613
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)				$ 17.58
Granted (in dollars per share)				23.12
Vested (in dollars per share)				16.95
Forfeited (in dollars per share)				19.42
Balance at the end of the period (in dollars per share)			$ 19.16	$ 19.16
Unrecognized compensation expenses			$ 211.5	$ 211.5
Weighted average period of compensation expense expected to be recognized				3 years 4 months 13 days
Contingent Vesting Units Awards
Equity compensation
Units granted (in units)		1,333,334
Units
Granted (in units)		1,333,334
Restricted units with a market condition
Equity compensation
Units granted (in units)		666,666		1,333,334
Units
Balance at the beginning of the period (in units)				0
Granted (in units)		666,666		1,333,334
Vested (in units)				0
Forfeited (in units)				0
Balance at the end of the period (in units)			1,333,334	1,333,334
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)				$ 0.00
Granted (in dollars per share)				9.30
Vested (in dollars per share)				0.00
Forfeited (in dollars per share)				0.00
Balance at the end of the period (in dollars per share)			$ 9.30	$ 9.30
Unrecognized compensation expenses			$ 11.8	$ 11.8
Weighted average period of compensation expense expected to be recognized				3 years 4 months 17 days
Third Anniversary of Grant Date | Restricted units
Equity compensation
Annual award vesting percentage				33.33%
Third Anniversary of Grant Date | Restricted units with a market condition
Equity compensation
Units granted (in units)	666,667
Units
Granted (in units)	666,667
Weighted Average Grant Date Fair Value
Balance at the end of the period (in dollars per share)	$ 10.92	$ 10.92
First Anniversary of Grant Date | Restricted units
Equity compensation
Annual award vesting percentage				25.00%
First Anniversary of Grant Date | Restricted units with a market condition
Equity compensation
Units granted (in units)	666,667
Units
Granted (in units)	666,667
Weighted Average Grant Date Fair Value
Balance at the end of the period (in dollars per share)	$ 7.68	$ 7.68