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SUPPLEMENTAL FINANCIAL INFORMATION - Narrative (Details) - USD ($)
3 Months Ended 12 Months Ended
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue, Major Customer [Line Items]                      
Revenue $ 384,000 $ 486,000 $ 395,000 $ 393,000 $ 701,000 $ 423,000 $ 3,071,000 $ 1,670,000 $ 1,658,000 $ 5,865,000 $ 31,721,000
Contract with Customer, Liability $ 0       $ 0       0 0 2,720,000
Sales Revenue, Net | Customer Concentration Risk | Customer 1                      
Revenue, Major Customer [Line Items]                      
Revenue                 1,550,000 2,720,000 24,520,000
Sales Revenue, Net | Customer Concentration Risk | Customer 2                      
Revenue, Major Customer [Line Items]                      
Revenue                   770,000 5,030,000.00
Sales Revenue, Net | Customer Concentration Risk | Customer 3                      
Revenue, Major Customer [Line Items]                      
Revenue                   750,000 1,240,000
Sales Revenue, Net | Customer Concentration Risk | Customer 4                      
Revenue, Major Customer [Line Items]                      
Revenue                   740,000  
Sales Revenue, Net | United States | Geographic Concentration Risk                      
Revenue, Major Customer [Line Items]                      
Revenue                 $ 1,660,000 5,800,000 25,760,000
Sales Revenue, Net | Other | Geographic Concentration Risk                      
Revenue, Major Customer [Line Items]                      
Revenue                   $ 70,000.00 $ 5,030,000.00