Stock-Based Compensation (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Valuation and Expenses Information
Total stock-based compensation expense	$ 448	$ 553	$ 1,088	$ 1,133
Stock options
Assumptions used for fair values of employee stock options granted
Expected stock price volatility (as a percent)	71.00%	68.00%		68.00%
Expected stock price volatility,minimum (as a percent)			70.00%
Expected stock price volatility,maximum (as a percent)			71.00%
Expected option term	6 years	6 years	6 years	6 years
Risk-free interest rate (as a percent)		2.50%
Risk-free interest rate, minimum (as a percent)	0.90%		0.90%	2.50%
Risk-free interest rate, maximum (as a percent)	1.30%		1.40%	2.90%
Research and development
Valuation and Expenses Information
Total stock-based compensation expense	284	344	679	705
General and administrative
Valuation and Expenses Information
Total stock-based compensation expense	$ 164	$ 209	$ 409	$ 428