Stock Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Total stock-based compensation expenses	$ 21	$ 365	$ 656	$ 2,233
Research and development [Member]
Total stock-based compensation expenses	11	148	367	878
General and administrative [Member]
Total stock-based compensation expenses	$ 10	$ 217	$ 289	$ 1,355