STOCKHOLDERS' EQUITY - Stock Option Activity and Stock-based Compensation Expense Narrative (Details) - USD ($)	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value, options exercised	$ 0	$ 0
Weighted-average grand date fair value of options granted in the period (USD per share)	$ 2.83	$ 6.73
Unrecognized compensation expense related to unvested stock options	$ 8,300,000
Unrecognized compensation expense, recognition period	2 years 1 month 6 days
Unvested restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested stock options	$ 800,000
Unrecognized compensation expense, recognition period	1 year 9 months 18 days

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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
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Amount of cost to be recognized for option under share-based payment arrangement.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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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.

+ References

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