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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income (loss) to common stockholders	$ (1,970)	$ 7,039	$ (7,972)	$ 35,332
Denominator:
Weighted-average common shares, basic (in shares)	27,609,068	27,503,356	27,601,760	27,610,924
Weighted-average common shares, diluted (in shares)	27,609,068	29,737,679	27,601,760	30,010,329
Net income (loss) per common share:
Basic (in dollars per share)	$ (0.07)	$ 0.26	$ (0.29)	$ 1.28
Diluted (in dollars per share)	$ (0.07)	$ 0.24	$ (0.29)	$ 1.18
Antidilutive securities (in shares)	5,199,525	3,325,815	5,199,525	3,160,733
Restricted stock units
Net income (loss) per common share:
Antidilutive securities (in shares)		613,712		613,712
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