COMMON STOCK, TRANSACTIONS (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	Jan. 25, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Apr. 16, 2018
Common stock disclosures
Common stock, par value (in dollars per share)		$ 0.00001		$ 0.00001	$ 0.00001
Proceeds from issuance of common stock, net of issuance costs		$ 2,510
Proceeds from issuance of stock under ESPP		$ 3	$ 29
Proceeds from exercise of stock options			$ 17
Common Stock
Common stock disclosures
Issuance of common stock to 401(k) plan (in shares)		440		3,933
Issuance of common stock to 401(k) plan		$ 6		$ 183
Stock issued under ESPP (in shares)		188		710
Proceeds from issuance of stock under ESPP		$ 3		$ 51
Issuance of common stock upon exercise of stock options (in shares)				3,576
Proceeds from exercise of stock options				$ 26
Issuance of common stock upon exercise of warrants (in shares)				139
Proceeds from exercise of warrants				$ 3
Issuance of stock in exchange for warrants (in shares)				80,857
Number of shares into which a warrant may be converted				23,102
Common Stock | Purchase and registration rights agreement
Common stock disclosures
Aggregate proceeds	$ 15,000
Common stock, par value (in dollars per share)	$ 0.00001
Term	24 months
Issuance of stock in public offering (in shares)	17,192	173,474
Deferred offering costs	$ 530
Proceeds from issuance of common stock, net of issuance costs		$ 2,510