EQUITY COMPENSATION (Restricted Units) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity compensation
Dividend declared and paid per share of Class A common stock (in dollar per share)	$ 0.40	$ 0.32
Distribution equivalents made to holders	$ 6.4
Restricted units
Units
Balance at the beginning of the period (in units or shares)	16,810,473
Granted (in units)	3,268,133
Vested (in units)	(3,921,722)
Forfeited (in units)	(211,925)
Balance at the end of the period (in units or shares)	15,944,959
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)	$ 20.07
Granted (in dollars per share)	36.85
Vested (in dollars per share)	19.21
Forfeited (in dollars per share)	21.42
Balance at the end of the period (in dollars per share)	$ 23.69
Unrecognized compensation expenses	$ 291.3
Weighted average period of compensation expense expected to be recognized	3 years 2 months 1 day
Third Anniversary of Grant Date | Restricted units
Equity compensation
Annual award vesting percentage	33.33%
First Anniversary of Grant Date | Restricted units
Equity compensation
Annual award vesting percentage	25.00%
First Anniversary | Restricted units
Equity compensation
Annual award vesting percentage	33.33%