SUMMARY OF SIGNIFICANT ACCOUNTING AND BUSINESS POLICIES - Receivables and Credit Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 9,015	$ 8,160	$ 9,364
Charged to costs and expenses	2,368	3,367	180
Charged to other accounts	(86)	22	(17)
Deductions	(1,171)	(2,534)	(1,367)
Balance at end of year	$ 10,126	$ 9,015	$ 8,160