STOCKHOLDERS' EQUITY (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	12 Months Ended
	Oct. 23, 2009	Dec. 31, 2012 Stock options	Dec. 31, 2011 Stock options	Dec. 31, 2010 Stock options	Dec. 31, 2012 Stock options Minimum	Dec. 31, 2011 Stock options Minimum	Dec. 31, 2012 Stock options Maximum	Dec. 31, 2011 Stock options Maximum
STOCKHOLDERS' EQUITY
Number of shares issued in a secondary offering	11,775,000
Price of shares issued (in dollars per share)	$ 2.60
Aggregate proceeds from issuance of shares after deducting underwriters' commission and offering expenses	$ 28.7
Stockholders' equity
Shares issued from exercise of options		658,510	155,935	249,671
Exercise price (in dollars per share)		$ 1.27	$ 0.79	$ 0.51	$ 0.51	$ 0.51	$ 2.42	$ 2.42