STOCKHOLDERS' EQUITY (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
STOCKHOLDERS' EQUITY
Performance periods over which awards will be awarded	3 years
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 5,311	$ 15,249	$ 13,718
Service-based stock options and restricted stock awards
Stock-Based Compensation Expense
Option vesting period	4 years
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	2,336	5,799	6,625
Restructuring charges
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	107	174
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense included in operating expenses	$ 2,868	$ 9,276	$ 7,093