STOCKHOLDERS' EQUITY (Details) (USD $)	1 Months Ended	2 Months Ended	12 Months Ended				1 Months Ended				12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended
	May 30, 2011	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Apr. 30, 2010	Feb. 28, 2013 Subsequent event	Jan. 31, 2013 Subsequent event	Dec. 31, 2012 Class C Preferred Stock	Dec. 31, 2012 Series C-1 Preferred Stock	Dec. 31, 2012 Cantor Agreement	Dec. 31, 2011 Cantor Agreement	Jan. 31, 2011 Cantor Agreement	Sep. 30, 2012 Cantor Amendment	Dec. 31, 2012 Cantor Amendment	Feb. 28, 2013 Cantor Amendment Subsequent event	Jan. 31, 2013 Cantor Amendment Subsequent event	Dec. 31, 2012 Shareholder Rights Plan item	Dec. 31, 2012 Shareholder Rights Plan Minimum	Dec. 31, 2012 Shareholder Rights Plan Series C-1 Preferred Stock item	Dec. 31, 2012 Shareholder Rights Plan Series C-1 Preferred Stock Minimum
Stockholders' Equity
Maximum value of securities for which the entity filed a shelf registration statement			$ 200,000,000			$ 150,000,000
Common stock issued (in shares)			64,359,513	44,210,636							4,425,000	575,000			3,578,290		2,433,608
Common stock available for sale (in shares)													5,000,000
Net proceeds from sale of common stock			83,784,000	36,023,000	1,014,000		97,000,000	17,100,000			19,000,000	2,200,000			21,100,000		17,100,000
Aggregate offering price of additional shares which the entity can issue as per amended agreement														44,000,000		4,400,000
Fixed commission rate (as a percent)														0.030
Notice period for termination of agreement														10 days
Lock-up period to be waived by underwriters																90 days
Common stock in an underwritten public offering issued (in shares)	11,500,000	12,075,000					13,800,000
Shares issued on exercise of over-allotment option by underwriters (in shares)	1,500,000	1,575,000					1,800,000
Net proceeds from sale of stock in an underwritten public offering	$ 33,700,000	$ 43,400,000	$ 43,483,000	$ 33,695,000			$ 97,000,000
Preferred stock, shares authorized			3,000,000	3,000,000					3,000,000	350,000
Shareholder Rights Plan
Number of preferred stock purchase rights for each outstanding share of common stock																				1
Number of shares callable by rights																				0.0001
Exercise price (in dollars per unit)																				35.00
Percentage of common stock to be acquired for rights to be exercisable																					15.00%
Percentage of common stock to be acquired in a tender offer for rights to be exercisable																					15.00%
Number of multiples of the exercise price that the Right holder has right to receive in value if 15% or more of the outstanding common stock is acquired																				2
Percentage of assets or earning power sold allowing the Right holder a right to receive common stock of the acquiring company																			50.00%
Number of multiples of the exercise price that the Right holder has a right to receive in value of the acquiring company's common stock																		2