SUMMARY OF SIGNIFICANT ACCOUNTING AND BUSINESS POLICIES - Variable Interest Entity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Assets	$ 851,861	$ 788,220
Fixed assets	56,899	63,703
Income tax benefit	$ 18,441	(10,894)	$ (13,185)
Employees
Risks and Uncertainties [Abstract]
Ownership percentage in VIE	52.50%
Variable Interest Entity, Primary Beneficiary
Risks and Uncertainties [Abstract]
Ownership percentage in VIE	47.50%
Assets	$ 4,800
Fixed assets	3,400
Increase (decrease) in cost of sales	800	(400)
Income tax benefit	$ 116	$ 83