EQUITY COMPENSATION (Restricted Units) (Details) - Restricted units $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Equity compensation
Distribution equivalents made to holders | $	$ 6.6
Units
Balance at the beginning of the period (in units) | shares	13,751,888
Granted (in units) | shares	3,635,419
Vested (in units) | shares	(835,124)
Forfeited (in units) | shares	(199,637)
Balance at the end of the period (in units) | shares	16,352,546
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	23.61
Vested (in dollars per share) | $ / shares	15.33
Forfeited (in dollars per share) | $ / shares	19.83
Balance at the end of the period (in dollars per share) | $ / shares	$ 18.98
Unrecognized compensation expenses | $	$ 233.3
Weighted average period of compensation expense expected to be recognized	3 years 8 months 12 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%