SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Allowance for Sales Returns and Exchanges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Sales Returns and Exchanges	$ 9,306	$ 8,230	$ 9,003	$ 9,916
Additions to the allowance	10,746	15,999	12,121
Deductions against the allowance	$ (9,670)	$ (16,772)	$ (13,034)