Stock Plans (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expenses	$ 543	$ 678	$ 2,581
Increase in basic net income (loss) per share (in dollars per share)	$ (0.01)	$ (0.01)	$ (0.04)
Increase in diluted net income (loss) per share (in dollars per share)	$ (0.01)	$ (0.01)	$ (0.04)
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expenses	245	378	1,021
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expenses	$ 298	$ 300	$ 1,560