SHAREHOLDERS EQUITY - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended
	Sep. 10, 2018	Jul. 26, 2018	Jul. 23, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Common stock par value				$ 0		$ 0
Issuance of common stock, net of issuance costs					$ 1,909
Common stock issuance costs					$ 7
Preferred Stock, shares outstanding				0		0
Convertible Preferred Stock Converted to Other Securities		$ 25,000
Series A preferred stock
Class of Stock [Line Items]
Preferred Stock, shares outstanding		8,559
Series B preferred stock
Class of Stock [Line Items]
Preferred Stock, shares outstanding		428
Series C preferred stock
Class of Stock [Line Items]
Preferred Stock, shares outstanding		11,881
Series D
Class of Stock [Line Items]
Preferred Stock, shares outstanding		41,000		0		0
Common Stock
Class of Stock [Line Items]
Common stock par value				$ 0.00
Number of votes per each share				one
Issuance of common stock (in shares)				0
Make whole share issuance	128,978
Common Stock | Private Placement
Class of Stock [Line Items]
Issuance of common stock (in shares)					67,242
Issuance of common stock, net of issuance costs				$ 1,900
Common Stock | IPO
Class of Stock [Line Items]
Issuance of common stock (in shares)			1,921,775
Issuance of common stock, net of issuance costs			$ 32,500
Common stock issuance costs			$ 4,400
Common stock price (in dollars per share)			$ 19.00
Common Stock | Underwriters option
Class of Stock [Line Items]
Issuance of common stock (in shares)			296,250