EQUITY STRUCTURE AND ACCOUNTS - Schedule of Treasury Stock Repurchase Activity (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Oct. 30, 2014	Feb. 10, 2014
Class of Stock [Line Items]
Share Price				$ 17.00
Shares Repurchase Program [Roll Forward]
Purchase of treasury stock	$ (4,652,000)	$ (994,000)
Class A common stock | Common Stock
Shares Repurchase Program [Roll Forward]
Treasury Stock, Shares, Acquired	424,000	84,000
2014 Share Repurchase Authorization Program
Class of Stock [Line Items]
Percentage of Aggregate Common Stock Outstanding Under Repurchase Program	5.80%
2014 Share Repurchase Authorization Program | Class A common stock
Class of Stock [Line Items]
Authorized amount of stock repurchase			$ 50,000,000
Shares Repurchase Program [Roll Forward]
Authorizations remaining as of December 31, 2015	$ 49,006,000
Treasury Stock, Shares, Acquired	424,317
Purchase of treasury stock	$ (4,653,000)
Authorizations remaining as of June 30, 2016	$ 44,353,000	$ 49,006,000
2014 Share Repurchase Authorization Program | Class A common stock | Common Stock
Class of Stock [Line Items]
Share Price	$ 12.20
Shares Repurchase Program [Roll Forward]
Treasury Stock Acquired, Average Cost Per Share	$ 10.96