Consolidated Statements of Operations Parentheticals (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock-based compensation expense associated with research and development expense	$ 3,249	$ 3,170	$ 3,022
Stock-based compensation expense associated with general and administrative expense	$ 2,458	$ 2,308	$ 2,252