SHAREHOLDERS' EQUITY - FAIR VALUE ASSUMPTIONS FOR OPTIONS GRANTED (Details) - Stock options, all inclusive recipients - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Stock-based compensation
Weighted average grant-date fair value of options granted (in dollars per share)	$ 2.91	$ 2.94
Total unrecognized compensation cost related to non-vested stock option awards	$ 2,689
Weighted average period for recognition of compensation cost related to unvested stock awards	2 years 15 days
Assumptions used to estimate the fair values of options granted
Volatility rate, minimum (as a percent)	82.80%	79.70%
Volatility rate, maximum (as a percent)	93.90%	98.90%
Risk-free interest rate, minimum (as a percent)	1.95%	1.25%
Risk-free interest rate, maximum (as a percent)	2.28%	2.17%
Dividend yield (as a percent)	0.00%	0.00%
Expected life (in years)	5 years 10 months 13 days	5 years 10 months 13 days