NET INCOME (LOSS) PER COMMON SHARE, Schedule of Potentially Antidilutive Securities (Details)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities 21,525 27,517
Employee stock options [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities 2,309 5,068
Employee stock purchase plan [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities 0 173
Restricted stock and restricted stock units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities 1,359 4,419
Convertible notes [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Antidilutive securities 17,857 17,857