COMMON STOCK, TRANSACTIONS (Details) $ / shares in Units, $ in Thousands				1 Months Ended			2 Months Ended	12 Months Ended
	Mar. 12, 2018 USD ($)	Jan. 25, 2018 USD ($) $ / shares shares	Apr. 08, 2015 shares	Mar. 31, 2016 USD ($) $ / shares shares	Jul. 31, 2015 USD ($) shares	Jan. 31, 2015 USD ($) shares	Mar. 12, 2018 shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Aug. 11, 2017 shares
Common stock disclosures
Proceeds from exercise of stock options | $								$ 26	$ 191	$ 1,068
Proceeds from exercise of warrants | $								3		7,789
Issuance of common stock to 401(k) plan | $								183	208	201
Proceeds from issuance of stock under ESPP | $								$ 51	$ 91
Common stock, par value (in dollars per share) | $ / shares								$ 0.00001	$ 0.00001
Proceeds from issuance of common stock and warrants | $									$ 29,905	$ 14,480
Common Stock
Common stock disclosures
Issuance of common stock upon exercise of stock options (in shares)								89,387	135,205	316,177
Proceeds from exercise of stock options | $								$ 26	$ 191	$ 1,068
Issuance of common stock upon exercise of warrants (in shares)								3,464		1,379,575
Proceeds from exercise of warrants | $								$ 3		$ 7,789
Issuance of common stock upon cashless exercise of warrants (in shares)									4,979	25,052
Issuance of common stock to 401(k) plan (in shares)								98,319	37,528	17,437
Issuance of common stock to 401(k) plan | $								$ 183	$ 208	$ 201
Stock issued under ESPP (in shares)								17,750	16,729
Proceeds from issuance of stock under ESPP | $								$ 51	$ 91
Issuance of stock in exchange for warrants (in shares)								2,021,419
Number of shares into which a warrant may be converted								577,548		1,354,523	48,507
Issuance of stock in public offering (in shares)										2,388,245
Number of shares for stock options in cashless exercise (in shares)										52,224
Issuance of stock for noncash exercise-stock options (in shares)										14,961
Issuance of stock for cash-stock options (in shares)										301,216
Number of warrants to purchase common stock (in shares)										40,955
Reverse stock split ratio			0.25
Stock issued during period, shares, reverse stock splits			1,514
Issuance of common stock for services (in shares)								350	365
Common Stock | Public offering
Common stock disclosures
Issuance of stock in public offering (in shares)						2,000,000
Net proceeds from issuance of equity (in dollars) | $						$ 11,038
Common Stock | Sales Agreement
Common stock disclosures
Issuance of stock in public offering (in shares)					388,245
Aggregate proceeds from sale agreement of shares of common stock | $					$ 50,000
Percentage of Commission on the gross proceeds from sales agreement of shares of common stock					3.00%
Net proceeds from issuance of equity (in dollars) | $										$ 3,442
Common Stock | Public Offering, March 2016
Common stock disclosures
Number of shares into which a warrant may be converted				2,146,666
Equity issuance (in price per unit) | $ / shares				$ 7.49
Warrants | Public Offering, March 2016
Common stock disclosures
Equity issuance (in price per unit) | $ / shares				0.01
Exercise price (in dollars per unit) | $ / shares				$ 10.00
Percentage of warrant exercises price over public offering price				133.00%
Common Stock And Warrants | Public Offering, March 2016
Common stock disclosures
Issuance of stock in public offering (in shares)				4,293,333
Proceeds from issuance of common stock and warrants | $				$ 29,905
Subsequent event | Common Stock | Purchase and registration rights agreement
Common stock disclosures
Aggregate proceeds | $		$ 15,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001
Term		24 months
Issuance of stock in public offering (in shares)		429,800					3,344,769
Net proceeds from issuance of equity (in dollars) | $	$ 2,252