NET INCOME (LOSS) PER SHARE ATTRIBUTABLE TO CLASS A COMMON SHAREHOLDERS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 30, 2014
Numerator:
Net income (loss) attributable to holders of shares of Class A common stock - basic	$ 10,090	$ 6,500	$ 22,557	$ (12,510)
Class A common stock
Numerator:
Net income (loss) attributable to holders of shares of Class A common stock - basic	10,090	6,500	22,557	(12,510)
Net income (loss) attributable to holders of shares of Class A common stock - diluted	$ 10,090	$ 6,500	$ 22,557	$ (12,510)
Denominator:
Weighted average shares of Class A common stock outstanding - basic	20,184,835	15,262,343	19,919,675	15,262,940
Weighted average number of incremental shares issuable from unvested restricted stock, RSUs and stock options, as calculated using the treasury stock method	1,281,186	942,911	1,185,848
Weighted average shares of Class A common stock outstanding-diluted	21,466,021	16,205,254	21,105,523	15,262,940
Net income (loss) per share attributable to holders of shares of Class A common stock
Basic (in dollars per share)	$ 0.50	$ 0.43	$ 1.13	$ (0.82)
Diluted (in dollars per share)	$ 0.47	$ 0.40	$ 1.07	$ (0.82)
Number of shares of common stock to be issued upon exchange of a partnership unit	1		1		1
Fully diluted shares of common stock outstanding if all Class A partnership units were to be exchanged for common stock immediately following the reorganization	55,398,692	55,197,575	55,303,354	54,254,664
Class A common stock | Stock options
Net income (loss) per share attributable to holders of shares of Class A common stock
Number of antidilutive securities excluded from calculation of diluted income (loss) per share	1,049,977	0	0	0
Class A common stock | RSUs
Net income (loss) per share attributable to holders of shares of Class A common stock
Number of antidilutive securities excluded from calculation of diluted income (loss) per share	15,397	11,644	7,945	665,649