EQUITY STRUCTURE AND ACCOUNTS - Dividends Declared (Details) - $ / shares							3 Months Ended			9 Months Ended
	Sep. 01, 2017	Jun. 01, 2017	Mar. 01, 2017	Sep. 01, 2016	Jun. 01, 2016	Mar. 01, 2016	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Class A common stock
Class of Stock [Line Items]
Dividends per share of common stock (in dollars per share)	$ 0.300	$ 0.300	$ 0.300	$ 0.275	$ 0.275	$ 0.275	$ 0.300	$ 0.46	$ 0.275	$ 0.900	$ 0.825