NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss) to common stockholders	$ 7,039	$ (6,755)	$ 35,332	$ 9,195
Denominator:
Weighted-average common shares, basic (in shares)	27,503,356	23,257,492	27,610,924	23,195,775
Weighted-average common shares, diluted (in shares)	29,737,679	23,257,492	30,010,329	24,233,724
Net income (loss) per common share:
Basic (in dollars per share)	$ 0.26	$ (0.29)	$ 1.28	$ 0.40
Diluted (in dollars per share)	$ 0.24	$ (0.29)	$ 1.18	$ 0.38
Antidilutive securities (in shares)			5,560,138	4,278,794
Restricted stock units
Net income (loss) per common share:
Antidilutive securities (in shares)	613,712		613,712	317,311
Stock options
Net income (loss) per common share:
Securities that are potentially dilutive to earnings per share (in shares)	1,620,611		1,785,693	720,637