EQUITY STRUCTURE AND ACCOUNTS - Dividends Declared (Details) - $ / shares							3 Months Ended		9 Months Ended
	Aug. 22, 2019	May 30, 2019	Feb. 27, 2019	Sep. 05, 2018	May 30, 2018	Feb. 27, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Class A Common Stock
Class of Stock [Line Items]
Dividends per share of Class A common stock (in dollars per share)	$ 0.340	$ 0.340	$ 0.340	$ 0.325	$ 0.325	$ 0.315	$ 0.340	$ 0.325	$ 1.020	$ 0.965