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SHARE-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding (in shares)	9,704		6,236
Share-based compensation expense	$ 407	$ 326
Unrecognized compensation cost, non-vested stock options	$ 2,900
Weighted-average period to recognize non-vested stock options	2 years 8 months 12 days
Weighted-average grant-date fair value of stock options granted (in dollars per share)	$ 0.56
Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding (in shares)	2,200
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (in shares)	9,704		6,236
2014 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Period exercisable from date of grant	10 years
Stock options outstanding (in shares)	9,600
Shares of common stock available for issuance (in shares)	5,400
2014 Stock Incentive Plan \| Vesting on the First Anniversary of Date of Grant \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting rate	25.00%
2014 Stock Incentive Plan \| Vesting at End of Each Successive Three-Month Period Thereafter \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting rate	6.25%
2009 Stock Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period exercisable from date of grant	10 years
Vested stock options outstanding (in shares)	100