Stock-Based Compensation (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Valuation and Expenses Information
Total stock-based compensation expense	$ 525	$ 570	$ 1,614	$ 1,703
Stock options
Assumptions used for fair values of employee stock options granted
Expected stock price volatility (as a percent)	71.00%	70.00%
Expected stock price volatility, minimum (as a percent)			70.00%	68.00%
Expected stock price volatility, maximum (as a percent)			71.00%	70.00%
Expected option term	6 years	6 years	6 years	6 years
Risk-free interest rate, minimum (as a percent)	1.20%	1.90%	0.90%	1.90%
Risk-free interest rate, maximum (as a percent)	1.30%	2.50%	1.40%	2.90%
Research and development
Valuation and Expenses Information
Total stock-based compensation expense	330	327	1,010	1,032
General and administrative
Valuation and Expenses Information
Total stock-based compensation expense	$ 195	$ 243	$ 604	$ 671