EQUITY COMPENSATION (Restricted Units) (Details) - Restricted units $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares
Equity compensation
Distribution equivalents made to holders | $	$ 5.8	$ 12.4
Units
Balance at the beginning of the period (in units) | shares		13,751,888
Granted (in units) | shares		3,681,702
Vested (in units) | shares		(1,903,923)
Forfeited (in units) | shares		(258,286)
Balance at the end of the period (in units) | shares	15,271,381	15,271,381
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares		$ 17.58
Granted (in dollars per share) | $ / shares		23.58
Vested (in dollars per share) | $ / shares		16.93
Forfeited (in dollars per share) | $ / shares		19.55
Balance at the end of the period (in dollars per share) | $ / shares	$ 19.07	$ 19.07
Unrecognized compensation expenses | $	$ 215.0	$ 215.0
Weighted average period of compensation expense expected to be recognized		3 years 5 months 23 days
Third Anniversary of Grant Date
Equity compensation
Annual award vesting percentage		33.33%
First Anniversary of Grant Date
Equity compensation
Annual award vesting percentage		25.00%