ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition and Deferred Commissions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred revenue	$ 8,600	$ 8,200
Deferred revenue associated with customer loyalty programs	6,406	7,033	$ 8,073
Deferred commissions	$ 3,880	$ 3,229
Customer returns, days after original sale date	90 days
Percentage of sale returns	1.50%