SUPPLEMENTAL FINANCIAL INFORMATION - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Revenue	$ 701	$ 423	$ 3,071	$ 1,670	$ 3,043	$ 451	$ 26,973	$ 1,254	$ 5,865	$ 31,721	$ 31,046
Deferred revenue	$ 0				$ 2,724				0	2,724
Sales Revenue, Net | Customer Concentration Risk | Customer 1
Revenue, Major Customer [Line Items]
Revenue									2,720	24,520	13,080
Sales Revenue, Net | Customer Concentration Risk | Customer 2
Revenue, Major Customer [Line Items]
Revenue									770	5,030	6,990
Sales Revenue, Net | Customer Concentration Risk | Customer 3
Revenue, Major Customer [Line Items]
Revenue									750	1,240	4,400
Sales Revenue, Net | Customer Concentration Risk | Customer 4
Revenue, Major Customer [Line Items]
Revenue									740
Sales Revenue, Net | United States | Geographic Concentration Risk
Revenue, Major Customer [Line Items]
Revenue									5,800	25,760	20,070
Sales Revenue, Net | Other | Geographic Concentration Risk
Revenue, Major Customer [Line Items]
Revenue									$ 70	$ 5,030	$ 4,400