ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Earnings Per Share (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
BASIC NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS
Net income attributable to common stockholders	$ 6,591	$ 23,590	$ 3,487	$ 1,035
Denominator:
Denominator for basic net income per share - weighted average outstanding shares	45,061,821	46,033,402	45,175,521	46,321,633
Effect of dilutive securities:
Stock options and restricted stock	639,834	2,405,291	809,418	2,456,165
Denominator for diluted net income per share - weighted-average outstanding shares	45,701,655	48,438,693	45,984,939	48,777,798
Net loss attributable to common stockholders per share - basic and diluted			$ 0.08
Net income attributable to common stockholders per share - basic	$ 0.15	$ 0.51	0.08	$ 0.02
Net income attributable to common stockholders per share -diluted	$ 0.14	$ 0.49	$ 0.08	$ 0.02