INCOME TAXES - Schedule of Net Operating Loss and Tax Credit Carryforwards (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Federal
Operating Loss and Tax Credit Carryforwards [Line Items]
Net operating losses	$ 105,972
State
Operating Loss and Tax Credit Carryforwards [Line Items]
Net operating losses	79,832
Research and Development | Federal
Operating Loss and Tax Credit Carryforwards [Line Items]
Tax credits	4,360
Research and Development | State
Operating Loss and Tax Credit Carryforwards [Line Items]
Tax credits	$ 4,934