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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Apr. 30, 2014
Numerator:
Net income (loss) attributable to holders of shares of Class A common stock - basic	$ 19,205	$ 9,489	$ 54,213	$ 23,352
Class A common stock
Numerator:
Net income (loss) attributable to holders of shares of Class A common stock - basic	19,205	9,489	54,213	23,352
Net income (loss) attributable to holders of shares of Class A common stock - diluted	$ 19,205	$ 9,489	$ 54,213	$ 23,352
Denominator:
Weighted average shares of Class A common stock outstanding - basic	32,505,940	20,926,745	29,094,514	20,807,189
Weighted average number of incremental shares issuable from unvested restricted stock, RSUs and stock options, as calculated using the treasury stock method	7,278,693	3,374,318	6,778,333	2,709,050
Weighted average shares of Class A common stock outstanding—diluted	39,784,633	24,301,063	35,872,847	23,516,239
Net income (loss) per share attributable to holders of shares of Class A common stock
Basic (in dollars per share)	$ 0.59	$ 0.45	$ 1.86	$ 1.12
Diluted (in dollars per share)	$ 0.48	$ 0.39	$ 1.51	$ 0.99
Number of Shares Issuable upon Exchange of Each 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	64,139,312	58,000,602	63,172,885	57,335,334
Class A common stock | Restricted stock and 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	25	2,552	8	1,211
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	0	973,859	0	1,048,196