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REVENUE (Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) customer	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) customer
Concentration Risk [Line Items]
Contract liability balances related to extended service contracts	$ 608		$ 331
Recognized revenue related to contract liability balances	0	$ 0
Contract assets	0		$ 0
Impairment losses on contract receivables	$ 0
Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Number of customer | customer	1		1
Concentration Risk, Benchmark Description	one customer with a trade account receivable balance greater than 10% of total accounts receivable		one customer with a trade account receivable balance greater than 10% of total accounts receivable
Concentration Risk, Percentage	13.00%		16.00%

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