SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 2,064	$ 2,009	$ 6,453	$ 5,752
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	462	653	1,696	1,932
Restructuring charges
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	5		307
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 1,597	$ 1,356	$ 4,450	$ 3,820