INCOME (LOSS) PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income / (loss)	$ 5,804	$ (37,351)	$ 37,995	$ 60,858	$ 45,521	$ 33,228	$ 19,901	$ 30,919	$ 67,306	$ 129,569	$ (47,084)
Denominator:
Weighted-average shares outstanding, basic	82,776	82,682	82,681	82,680	82,280	81,758	52,919		82,705	62,779
Basic net income / (loss) per share (in dollars per share):	$ 0.07	$ (0.45)	$ 0.46	$ 0.74	$ 0.55	$ 0.41	$ 0.38	$ 0.93	$ 0.81	$ 2.06	$ (1.54)
Numerator:
Net income / (loss)	$ 5,804	$ (37,351)	$ 37,995	$ 60,858	$ 45,521	$ 33,228	$ 19,901	$ 30,919	$ 67,306	$ 129,569	$ (47,084)
Net Income / (Loss), diluted									$ 67,306	$ 129,569
Denominator:
Weighted-average shares outstanding, basic	82,776	82,682	82,681	82,680	82,280	81,758	52,919		82,705	62,779
Add:
Restricted stock units										334
Weighted-average shares outstanding, diluted	82,776	82,682	82,681	82,680	82,778	82,480	52,940		82,705	63,113
Diluted net income / (loss) per share (in dollars per share):	$ 0.07	$ (0.45)	$ 0.46	$ 0.74	$ 0.55	$ 0.40	$ 0.38	$ 0.93	$ 0.81	$ 2.05	$ (1.54)
Class A common stock
Numerator:
Net income / (loss)											$ (17,402)
Denominator:
Weighted-average shares outstanding, basic								11,270			11,270
Basic net income / (loss) per share (in dollars per share):											$ (1.54)
Numerator:
Net income / (loss)											$ (17,402)
Reallocation of net loss as a result of assumed conversion of Class B to Class A shares, diluted											(29,682)
Net Income / (Loss), diluted											$ (47,084)
Denominator:
Weighted-average shares outstanding, basic								11,270			11,270
Add:
Assumed conversion of Class B to Class A shares											19,223
Weighted-average shares outstanding, diluted								33,273			30,493
Diluted net income / (loss) per share (in dollars per share):											$ (1.54)
Class B common stock
Numerator:
Net income / (loss)											$ (29,682)
Denominator:
Weighted-average shares outstanding, basic								22,003			19,223
Basic net income / (loss) per share (in dollars per share):											$ (1.54)
Numerator:
Net income / (loss)											$ (29,682)
Net Income / (Loss), diluted											$ (29,682)
Denominator:
Weighted-average shares outstanding, basic								22,003			19,223
Add:
Weighted-average shares outstanding, diluted								22,003			19,223
Diluted net income / (loss) per share (in dollars per share):											$ (1.54)