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
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net Income (Loss) Available to Common Stockholders, Basic	$ 28,293	$ 15,950
Denominator:
Weighted-average common shares, basic (in shares)	27,719,689	23,133,370
Weighted-average common shares, diluted (in shares)	30,284,175	23,216,528
Basic (in dollars per share)	$ 1.02	$ 0.69
Diluted (in dollars per share)	$ 0.93	$ 0.69
Antidilutive securities (in shares)	5,699,725	2,111,119
Restricted Stock Units
Denominator:
Antidilutive securities (in shares)	626,212
Stock options
Denominator:
Securities that are potentially dilutive to earnings per share (in shares)	1,938,274	572,501