STOCKHOLDERS' EQUITY - Additional information (Details)						1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 24, 2020 USD ($) $ / shares shares	Apr. 20, 2020 USD ($)	Feb. 28, 2020 tranche shares	Jul. 09, 2019 USD ($)	May 31, 2019 USD ($) $ / shares shares	Feb. 28, 2020 USD ($) shares	Jul. 22, 2019 USD ($) shares	Mar. 04, 2019 USD ($) shares	Feb. 28, 2018 USD ($) shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Jun. 30, 2019 shares	Jul. 26, 2018 USD ($)
Stockholders Equity [Line Items]
Number of preferred stock authorized | shares										5,000,000		5,000,000		5,000,000	5,000,000
Number of common stock authorized | shares					50,000,000					100,000,000		100,000,000		100,000,000	100,000,000
Number of shares issued | shares												4,301,869
Aggregate registered amount for offerings																$ 150,000,000
Average selling price | $ / shares										$ 6.53		$ 6.53
Net proceeds from issuance of stock												$ 27,238,000
Expenses incurred												49,000
Proceeds from Issuance of Common Stock												$ 27,238,000
Number of option granted | shares			1,041,325									1,593,825
Grant date fair value of these unvested options										$ 6,279,000		$ 6,279,000
Stock or Unit Option Plan Expense										419,000		$ 616,000
Percentage of Milestone Activity Met by the Company												62.50%
Share-Based Compensation Arrangement By Share Based Payment Award, Number Of Vesting Tranches | tranche			4
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term												10 years
Allocated Share-based Compensation Expense										$ 1,088,000	$ 802,000	$ 2,864,000	$ 1,175,000
Exercise price per share | $ / shares										$ 7.975		$ 7.975
Expected life of the stock option												10 years
expected dividends												0.00%
Risk free interest rate, minimum												0.28%
Risk free rate maximum												0.36%
Total unrecognized compensation cost related to stock options										$ 3,233,000		$ 3,233,000
Amortized period												30 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares | shares												691,135
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures										$ 328,841	237,729	$ 657,780	663,368
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | shares										5,234,948		5,234,948		4,218,189
Class of Warrant or Right, Outstanding | shares										0		0
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition												30 months
Underwritten public offering
Stockholders Equity [Line Items]
Number of shares issued | shares	6,052,631
Average selling price | $ / shares	$ 9.50
Gross Proceeds from issuance of stock	$ 57,500,000
Net proceeds from issuance of stock	53,800,000
Proceeds from Issuance of Common Stock	$ 53,800,000
February 28, 2018 Performance-Based Award [Member] | Restricted stock
Stockholders Equity [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares									146,200
Stock Issued During Period, Value, Restricted Stock Award, Gross									$ 1,148,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures										$ 0	96,000	$ (23,000)	298,000
March 4, 2019 Performance-Based Award [Member] | Restricted stock
Stockholders Equity [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares								22,220
Stock Issued During Period, Value, Restricted Stock Award, Gross								$ 179,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures										12,000	15,000	22,000	34,000
July 24,2020 Offering[Member] | Underwritten public offering
Stockholders Equity [Line Items]
Number of shares issued | shares	6,052,631
Average selling price | $ / shares	$ 9.50
Gross Proceeds from issuance of stock	$ 57,500,000
Net proceeds from issuance of stock	53,800,000
Proceeds from Issuance of Common Stock	$ 53,800,000
July 22, 2019 Performance-Based Award [Member] | Restricted stock
Stockholders Equity [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares							180,300
Stock Issued During Period, Value, Restricted Stock Award, Gross							$ 1,300,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures										256,000	103,000	461,000	525,000
February 28 2020 Performance Based Award [Member] | Restricted stock
Stockholders Equity [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares						168,100
Stock Issued During Period, Value, Restricted Stock Award, Gross						$ 1,014,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures										$ 84,000	$ 0	$ 535,000	$ 0
Cantor Fitzgerald and Co. [Member]
Stockholders Equity [Line Items]
Number of shares issued | shares					2,094,140
Average selling price | $ / shares					$ 8.72
Net proceeds from issuance of stock					$ 17,718,000
Proceeds from Issuance of Common Stock					$ 17,718,000
Jefferies LLC and B. Riley FBR, Inc [Member]
Stockholders Equity [Line Items]
Number of shares issued | shares												4,110,625		191,244
aggregate offering price		$ 50,000,000		$ 25,000,000
Average selling price | $ / shares										$ 6.64		$ 6.64		$ 4.11
Net proceeds from issuance of stock												$ 26,476,000		$ 762,000
Proceeds from Issuance of Common Stock												$ 26,476,000		$ 762,000
Commission rate (as a percent)				3.00%
Exercise Price Ranging From 5.68 To 6.57 [Member] | Maximum
Stockholders Equity [Line Items]
Exercise price per share | $ / shares										10.58		$ 10.58
Expected volatility												69.80%
Exercise Price Ranging From 5.68 To 6.57 [Member] | Minimum
Stockholders Equity [Line Items]
Exercise price per share | $ / shares										$ 5.68		$ 5.68
Expected volatility												64.80%