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STOCKHOLDERS' EQUITY - EQUITY PLANS (Details) - USD ($) | 1 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Feb. 28, 2022 | May 31, 2021 | Feb. 28, 2021 | Feb. 29, 2020 | Jan. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Mar. 31, 2022 | Jun. 30, 2020 | Oct. 31, 2018 | May 15, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares reserved for future issuance (in shares) |  |  |  |  |  |  | 133,292,810 |  |  |  |  |  |
Aggregate Intrinsic Value - Options Outstanding |  |  |  |  |  |  |  |  |  |  |  |  |
Closing stock price (in dollars per share) |  |  |  |  |  |  | $ 1.22 |  |  |  |  |  |
Total pretax intrinsic value of stock options exercised (in dollars) |  |  |  |  |  |  | $ 93,000 | $ 17,000 | $ 80,000 |  |  |  |
Cash received from exercise of stock options (in dollars) |  |  |  |  |  |  | $ 556,000 | $ 25,000 | $ 163,000 |  |  |  |
Number of Shares - Options Outstanding |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options exercisable at the end of the period (in shares) |  |  |  |  |  |  | 30,459,136 | 25,721,508 | 19,915,713 |  |  |  |
Weighted Average Exercise Price Per Share - Options Outstanding |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options exercisable at the end of the period (in dollars per share) |  |  |  |  |  |  | $ 2.35 | $ 2.54 | $ 2.86 |  |  |  |
2011 Plan |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options |  |  |  |  |  |  | 4 years |  |  |  |  |  |
2011 Plan | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Expiration term of stock options from date of grant |  |  |  |  |  |  | 10 years |  |  |  |  |  |
2018 Plan |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options |  |  |  |  |  |  | 4 years |  |  |  |  |  |
Common stock, shares reserved for future issuance (in shares) |  | 12,500,000 |  |  |  |  |  |  |  |  | 5,700,000 |  | 10,000,000
Minimum percentage of ownership required for granting stock options at least 110% of fair market value of common stock |  |  |  |  |  |  | 10.00% |  |  |  |  |  |
Minimum exercise price as a percentage of fair market value for employees having more than 10 % outstanding common stock |  |  |  |  |  |  | 110.00% |  |  |  |  |  |
Maximum expiration term of stock options granted to employees having more than 10 % outstanding common stock |  |  |  |  |  |  | 5 years |  |  |  |  |  |
2018 Plan | First Director Option |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options |  |  |  |  |  |  | 3 years |  |  |  |  |  |
Stock options to be granted to purchase shares upon appointment (shares) |  |  |  |  |  |  | 120,000 |  |  |  |  |  |
2018 Plan | First Director Option | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options to be granted to purchase shares upon appointment (shares) |  |  |  |  |  |  |  |  |  | 200,000 |  |  |
2018 Plan | Subsequent Director Option |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options to be granted to purchase shares (in shares) |  |  |  |  |  |  | 83,000 |  |  |  |  |  |
2018 Plan | Subsequent Director Option | Scenario Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options to be granted to purchase shares (in shares) |  |  |  |  |  |  |  |  |  | 125,000 |  |  |
2018 Plan | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Expiration term of stock options from date of grant |  |  |  |  |  |  | 10 years |  |  |  |  |  |
2006 Directors Plan | First Director Option |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options |  |  |  |  |  |  | 3 years |  |  |  |  |  |
2006 Directors Plan | Subsequent Director Option |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options |  |  |  |  |  |  | 1 year |  |  |  |  |  |
2006 Directors Plan | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Expiration term of stock options from date of grant |  |  |  |  |  |  | 10 years |  |  |  |  |  |
2018 Inducement Award Plan |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares reserved for future issuance (in shares) |  |  |  |  |  |  | 15,100,000 |  |  |  |  |  |
Common stock, increase in option reserves (in shares) |  | 5,000,000 | 800,000 | 1,300,000 | 5,000,000 | 3,000,000 |  |  |  |  |  |  |
2018 Inducement Award Plan | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares reserved for future issuance (in shares) | 16,100,000 |  |  |  |  |  |  |  |  |  |  |  |
Common stock, increase in option reserves (in shares) | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Directors Market Value Stock Purchase Plan |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common stock, shares reserved for future issuance (in shares) |  |  |  |  |  |  |  |  |  |  |  | 1,000,000 |
Directors Market Value Stock Purchase Plan | Restricted stock awards |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Shares issued (in shares) |  |  |  |  |  |  | 20,783 | 17,986 | 29,150 |  |  |  |
Granted (in dollars per share) |  |  |  |  |  |  | $ 1.38 | $ 1.60 | $ 1.50 |  |  |  |
Total fair value of restricted stock that vested |  |  |  |  |  |  | $ 29,000 | $ 29,000 | $ 44,000 |  |  |  |

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