STOCKHOLDERS EQUITY (Details) $ in Thousands	1 Months Ended		6 Months Ended
	Nov. 30, 2014 shares	Apr. 30, 2014 shares	Jun. 30, 2015 USD ($) shares	Dec. 31, 2014 shares
STOCKHOLDERS EQUITY
Treasury stock shares acquired | $			$ 5,953
Group LP
STOCKHOLDERS EQUITY
Number of units held by noncontrolling interest holders			33,977,246
Noncontrolling interests (as a percent)			63.00%
Share repurchase program authorized first quarter 2015
STOCKHOLDERS EQUITY
Treasury stock shares acquired (in shares)			192,660
Shares deemed to be repurchased for payment of tax liabilities			192,660
Treasury stock shares acquired | $			$ 5,953
Class A common stock
STOCKHOLDERS EQUITY
Aggregate stock issuance (in shares)		15,263,653
Reorganization of equity structure (in shares)		7,699,851
Common Stock issued in connection with settlement of appreciation rights issued in prior years (in shares)		88,802
Common stock, shares issued			20,353,760	19,770,893
Common stock, shares outstanding			20,161,100	19,770,893
Number of shares of common stock to be issued upon exchange of a partnership unit		1	1
Class A common stock | IPO
STOCKHOLDERS EQUITY
Common Stock issued (in shares)		7,475,000
Class A common stock | Secondary Offering
STOCKHOLDERS EQUITY
Common Stock issued (in shares)	6,325,000
Issuance of Class A common stock and acquisition of Class A partnership units in connection with secondary offering (in shares)	4,511,058
Class A common stock | Group LP
STOCKHOLDERS EQUITY
Common stock, shares outstanding			20,161,100
Class B common stock
STOCKHOLDERS EQUITY
Common Stock issued (in shares)		36,158,698
Common stock, shares issued			31,402,673	31,621,542
Common stock, shares outstanding			31,402,673	31,621,542
Ratio of subscription price to the initial public offering price of shares of common stock		0.00055
Aggregate number of shares of Class B common stock that may be converted into Class A common stock		20,000
Dividends payable ratio to outstanding shares of publicly traded common stock		0.00055