STOCKHOLDERS' EQUITY - STOCK-BASED COMPENSATION EXPENSE FOR EMPLOYEES AND DIRECTORS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 8,397,000	$ 7,658,000	$ 4,435,000
Stock options
Stock-Based Compensation Expense
Non-cash stock-based compensation expense			205,000
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	2,139,000	2,545,000	1,741,000
Restructuring charges
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	307,000		28,000
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 5,951,000	$ 5,113,000	$ 2,666,000