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CONVERTIBLE NOTES - Bridge Notes (Details) |  |  |  |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |
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Mar. 26, 2020 $ / shares | Mar. 25, 2020 $ / shares | May 14, 2019 USD ($) D $ / shares shares | Apr. 16, 2019 USD ($) D $ / shares shares | Apr. 30, 2019 $ / shares | Apr. 30, 2018 $ / shares shares | Dec. 31, 2020 USD ($) $ / shares shares | Dec. 31, 2019 USD ($) shares | May 14, 2020 USD ($) | Apr. 20, 2020 USD ($) | Apr. 16, 2020 USD ($) | Mar. 31, 2020 $ / shares | Feb. 29, 2020 $ / shares | Apr. 15, 2019 $ / shares | Mar. 31, 2019 $ / shares | Dec. 31, 2018 USD ($) $ / shares | Oct. 03, 2017 $ / shares
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of debt |  |  |  |  |  |  |  | $ 2,150,000 |  |  |  |  |  |  |  |  |
Total debt |  |  |  |  |  |  | $ 1,010,000 | 519,000 |  |  |  |  |  |  |  |  |
Loss on extinguishment of convertible notes |  |  |  |  |  |  | (1,225,000) |  |  |  |  |  |  |  |  |  |
Loss on modification of warrants |  |  |  |  |  |  |  | (1,128,000) |  |  |  |  |  |  |  |  |
Proceeds from convertible notes |  |  |  |  |  |  |  | 2,150,000 |  |  |  |  |  |  |  |  |
Loss on extinguishment of convertible notes |  |  |  |  |  |  | (1,225,000) |  |  |  |  |  |  |  |  |  |
Conversion of convertible debt, plus interest, into common stock |  |  |  |  |  |  | 2,176,000 | 7,553,000 |  |  |  |  |  |  |  |  |
Long-term debt, net of current maturities |  |  |  |  |  |  | $ 362,000 | 198,000 |  |  |  |  |  |  |  |  |
Convertible Promissory Note Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 45.00
Convertible Promissory Note Warrants | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  | $ 0.40 | $ 2.25 |  |  |  |
April 2018 Warrants, First Half |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Term |  |  |  |  | 1 year | 5 years |  |  |  |  |  |  |  |  |  |  |
April 2018 Warrants, Second Half |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Term |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |
Warrants term |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |
April 2018 Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock rights issued (in shares) | shares | shares |  |  |  |  |  | 243,224 |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  | $ 11.25 |  |  |  |  |  |  |  |  |  |  |
Loss on modification of warrants |  |  |  |  |  |  |  | 1,100,000 |  |  |  |  |  |  |  |  |
Amended Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  | $ 5.40 |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants term |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |
Quarter 3 2018 Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  | $ 5.40 |  |  |  |  |  |  |  |  |  | $ 7.50 |  |
April 2019 Bridge Notes And May 2019 Bridge Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guaranteed interest period | 18 months | 12 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2018 Note Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, face amount |  |  |  |  |  |  |  |  |  | $ 4,500,000 |  |  |  |  |  |  |
2018 Note Agreement | Advisor Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock rights issued (in shares) | shares | shares |  |  |  |  |  | 15,466 |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  | $ 11.25 |  |  |  |  |  |  |  |  |  |  |
May 2019 Bridge Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock rights issued (in shares) | shares | shares |  |  | 154,343 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants, fair value |  |  | $ 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  | $ 9.56 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants term |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt |  |  |  |  |  |  |  | 142,000 |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | Quarter 3 2018 Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  | $ 11.25 |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | Quarter 4 2018 Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5.40 |
Warrants term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |
Convertible Debt [Member] | April 2019 Bridge Notes And May 2019 Bridge Notes | Amendment Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt discount |  |  |  |  |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |
Beneficial conversion feature |  |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |  |  |
Loss on extinguishment of convertible notes |  |  |  |  |  |  | 1,200,000 |  |  |  |  |  |  |  |  |  |
Convertible Debt, Fair Value Disclosures |  |  |  |  |  |  | 2,600,000 |  |  |  |  |  |  |  |  |  |
Floor price | $ / shares | $ 0.40 | $ 2.25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of convertible debt |  |  |  |  |  |  | 2,600,000 |  |  |  |  |  |  |  |  |  |
Debt premium on debt |  |  |  |  |  |  | 800,000 |  |  |  |  |  |  |  |  |  |
Loss on extinguishment of convertible notes |  |  |  |  |  |  | 1,200,000 |  |  |  |  |  |  |  |  |  |
Beneficial conversion |  |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Premium |  |  |  |  |  |  | 800,000 |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | April 2019 Bridge Notes And May 2019 Bridge Notes | Amendment Agreement | Bridge Notes Beneficial Conversion Features |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt, Fair Value Disclosures |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |
Fair value of convertible debt |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | April 2019 Bridge Notes And May 2019 Bridge Notes | Amendment Agreement | Bridge Notes Redemption Feature [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt, Fair Value Disclosures |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |
Fair value of convertible debt |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | Convertible Bridge Loan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt discount |  |  |  |  |  |  |  | $ 1,796,000 |  |  |  |  |  |  |  | $ 1,111,000 |
Exercise price (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7.50 |  |  |
Debt premium on debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 647,000 |
Warrant liability canceled due to settlement of equity instruments |  |  |  |  |  |  | $ 2,200,000 |  |  |  |  |  |  |  |  |  |
Number of shares converted from debt instrument (in shares) | shares |  |  |  |  |  |  | 3,908,145 | 1,900,766 |  |  |  |  |  |  |  |  |
Conversion of convertible debt, plus interest, into common stock |  |  |  |  |  |  |  | $ 4,800,000 |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Premium |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 647,000 |
Warrants term |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization of debt discount |  |  |  |  |  |  | $ 703,000 | 273,000 |  |  |  |  |  |  |  |  |
Amortization of debt premium |  |  |  |  |  |  | $ 385,000 | 167,000 |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | Quarter 3 2018 Bridge Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beneficial conversion feature |  |  |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |  |
Beneficial conversion |  |  |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | April 2019 Bridge Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, face amount |  |  |  |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |  |  |
Discount percentage |  |  |  | 9.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment Period |  |  |  | 180 days |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of debt |  |  |  | $ 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt |  |  |  | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt discount and debt issuance costs as a reduction of the related debt |  |  |  | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt discount |  |  |  | $ 100,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Stock rights issued (in shares) | shares | shares |  |  |  | 147,472 |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants, fair value |  |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price (in dollars per share) | $ / shares |  |  |  | $ 5.40 |  |  |  |  |  |  |  |  |  |  |  |  |
Beneficial conversion feature |  |  |  | $ 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Net debt issuance costs and debt discounts |  |  |  | 2,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on issuance of convertible notes |  |  |  |  |  |  |  | 1,000,000 |  |  |  |  |  |  |  |  |
Proceeds from convertible notes |  |  |  | 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Beneficial conversion |  |  |  | $ 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants term |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | April 2019 Bridge Notes | Amendment Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion threshold percentage of stock price trigger |  |  |  | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible debt, threshold consecutive trading days | D |  |  |  | 10 |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion price per share | $ / shares |  |  |  | $ 0.75 |  |  |  |  |  |  |  |  |  |  |  |  |
Floor price | $ / shares |  |  |  | 2.25 |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | April 2019 Bridge Notes | Maximum | Amendment Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion price per share | $ / shares |  |  |  | $ 3.75 |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible Debt [Member] | May 2019 Bridge Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, face amount |  |  | $ 1,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion threshold percentage of stock price trigger |  |  | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible debt, threshold consecutive trading days | D |  |  | 10 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion price per share | $ / shares |  |  | $ 7.12 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment Period |  |  | 180 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of debt |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt discount and debt issuance costs as a reduction of the related debt |  |  | 1,100,000 |  |  |  |  |  | $ 1,100,000 |  |  |  |  |  |  |  |
Debt discount |  |  | 100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beneficial conversion feature |  |  | 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net debt issuance costs and debt discounts |  |  | $ 2,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on issuance of convertible notes |  |  |  |  |  |  |  | $ 900,000 |  |  |  |  |  |  |  |  |
Original issue discount (as a percent) |  |  | 9 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from convertible notes |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Floor price | $ / shares |  |  | $ 2.25 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beneficial conversion |  |  | $ 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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