STOCK-BASED COMPENSATION - Narrative (Details)	12 Months Ended
Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of available shares consumed for each restricted stock and restricted stock units issued	1.75
Intrinsic value of stock options exercised \| $	$ 100,000	$ 200,000
Expected dividend yield	0.00%
Unrecognized compensation cost \| $	$ 6,600,000
Unrecognized compensation cost, recognized over an estimated weighted-average period	1 year 10 months 24 days
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period	4 years
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period	7 years
Time-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share) \| $ / shares	$ 2.21	$ 3.69
Intrinsic value of stock options exercised \| $	$ 2,273,000
RSAs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period	1 year
Shares of PSUs granted (in shares)	142,000
PSUs outstanding (in shares)	130,000	91,000
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period	3 years
Shares of PSUs granted (in shares)	515,000
PSUs outstanding (in shares)	802,000	945,000
Market Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of PSUs granted (in shares)	250,000
Award vesting rights, percentage	25.00%
PSUs outstanding (in shares)	250,000
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value on the purchase date	85.00%
Maximum number of shares per employee (in shares)	2,000
Maximum value of shares per employee \| $	$ 25,000
Common stock reserved for issuance (in shares)	1,000,000.0
Purchases under ESPP (in shares)	22,556
Average purchase price (in dollars per share) \| $ / shares	$ 5.96
Shares available for purchase (in shares)	230,881

The reduction in number of available shares when a share is issued under the share based compensation.

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The estimated dividend rate (a percentage of the share price) used in option-pricing model.

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Average Purchase Price

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Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Amount

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Share-based Compensation Arrangement by Share-based Payment Award, Shares Available For Purchase

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Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The highest quantity of shares an employee can purchase under the plan per period.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of shares purchased for issuance under share-based payment arrangement.

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Percentage of vesting of award under share-based payment arrangement.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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