EQUITY BASED COMPENSATION - Rockwater awards (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restricted Stock
Assumptions for equity options granted:
Equity-based compensation expense	$ 1.9	$ 2.2	$ 3.8	$ 4.0
Equity options
Assumptions for equity options granted:
Equity-based compensation expense	$ 0.0	$ 1.0	$ 0.2	$ 2.3
Equity options | Class A Common Stock
Assumptions for equity options granted:
Underlying Equity	$ 4.90		$ 4.90		$ 9.28