CONVERTIBLE PROMISSORY NOTES - Narrative (Details) - USD ($)		1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Aug. 31, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Aug. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Short-term Debt [Line Items]
Proceeds from issuance of convertible promissory notes						$ 7,397,000	$ 0
Warrant liability		$ 1,500,000	$ 0			0		$ 242,000
Derivative liability, fair value		$ 1,400,000
Gain on extinguishment			$ 2,318,000	$ 0		$ 2,318,000	$ 0
Convertible Promissory Notes
Short-term Debt [Line Items]
Stated rate		12.00%
Debt term		1 year
Conversion price (in usd per share)	$ 7.54	$ 31.05			$ 7.54
Qualified financing threshold		$ 15,000,000.0
Conversion price as percent of price paid per share		80.00%
Share price threshold (in usd per share)		$ 38.82
Proceeds from issuance of convertible promissory notes					$ 7,400,000
Coverage percent		50.00%
Stock issuable upon warrants (in shares)		490,683
Term of warrants		5 years
Exercise price (in usd per share)	$ 42.70	$ 10.36			$ 42.70
Premium percentage on effective price	10.00%
Effective rate			12.00%			12.00%
Interest expense			$ 1,100,000			$ 2,000,000.0
Accretion of discounts			$ 400,000			$ 800,000
Gain on extinguishment	$ 2,300,000
Convertible Promissory Notes | Common Stock
Short-term Debt [Line Items]
Shares issued in conversion (in shares)	1,069,740