STOCK-BASED COMPENSATION PLANS - Summary of stock option activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Summary of stock option activity under the option Plan
Outstanding at ending	1,316
Number of Shares, Exercisable	656
Weighted Average Exercise Price, Granted		$ 4.37
Employee Stock Option [Member]
Summary of stock option activity under the option Plan
Outstanding at beginning	1,855
Number of Shares, Granted	14
Number of Shares, Forfeited	(175)
Number of Warrants, Exercised	(378)
Outstanding at ending	1,316		1,855
Number of Shares, Exercisable	656
Weighted Average Exercise Price, Outstanding Beginning	$ 2.48
Weighted Average Exercise Price, Granted	10.15
Weighted Average Exercise Price, Forfeited	5.40
Weighted Average Exercise Price, Exercised	0.58
Weighted Average Exercise Price, Outstanding Ending	2.72		$ 2.48
Weighted Average Exercise Price, Exercisable	$ 1.00
Weighted Average Remaining Contractual Life, Outstanding	7 years 2 months 5 days		6 years 5 months 1 day
Weighted Average Remaining Contractual Life, Exercisable (Years)	5 years 9 months 22 days
Aggregate Intrinsic Value, Outstanding	$ 10,991		$ 10,032
Aggregate Intrinsic Value, Exercisable	$ 6,604