STOCK-BASED COMPENSATION - Stock options (Details) - Stock Options	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Stock Option Awards
Balance at the beginning of the period | shares	2,169,243
Balance at the end of the period | shares	2,169,243
Exercisable at end of the period | shares	1,148,859
Unrecognized cost inclusive of directors' awards | $	$ 1,829,000
Weighted average remaining recognition period (years)	1 year 5 months 23 days
Weighted Average Exercise Price
Balance at the beginning of the period | $ / shares	$ 9.87
Balance at the end of the period | $ / shares	9.87
Exercisable at end of the period | $ / shares	$ 10.01
Weighted Average Remaining Contractual Term (years)
Weighted average remaining contractual term, balance (years)	8 years
Exercisable at end of the period	7 years 8 months 12 days
Stock Option Awards, Nonvested
Balance at the beginning of the period | shares	1,196,545
Vested | shares	(176,161)
Balance at the end of the period | shares	1,020,384
Weighted Average Exercise Price, Nonvested
Balance at the beginning of the period | $ / shares	$ 2.66
Vested | $ / shares	2.47
Balance at the end of the period | $ / shares	$ 2.70