SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 1,478	$ 958	$ 1,339	$ 1,226
Bad debt (recovery) expense	1,298	208	119
Increase (reduction) in allowance for doubtful accounts	$ (778)	$ (589)	$ (6)