COMMON STOCK OFFERING, RESTRICTED STOCK UNITS, STOCK OPTIONS AND WARRANTS - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Shares
Granted (shares)	396
Forfeited (shares)	(129)
Expired (shares)	(48)
Vested at end of period (shares)	300
Stock Options Plans
Shares
Outstanding at beginning of period (shares)	6,824
Granted (shares)	396
Forfeited (shares)	(129)
Expired (shares)	(48)
Exercised (shares)	(287)
Outstanding at end of period (shares)	6,756	6,824
Vested at end of period (shares)	4,587
Price
Outstanding at beginning of period (USD per share)	$ 5.92
Granted (USD per share)	5.10
Forfeited (USD per share)	5.99
Expired (USD per share)	7.16
Exercised (USD per share)	1.31
Outstanding at end of period (USD per share)	6.06	$ 5.92
Vested (USD per share)	$ 5.95
Term
Term of outstanding options	5 years 9 months 18 days	5 years 7 months 6 days
Term of vested options (years)	4 years 1 month 6 days
Aggregate intrinsic value of stock options outstanding	$ 4.1
Aggregate intrinsic value of vested stock options	$ 3.3

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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