CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Non-cash stock-based compensation expenses included in operating expenses are as follows:
Research and development	$ 8,041	$ 10,921	$ 11,689
General and administrative	$ 4,319	$ 5,755	$ 7,429