Geographic Information (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011
Revenue earned
Revenue earned from the REFABB grant	$ 2,490	$ 1,971	$ 918
Number of additional customers	3
U.S. Department of Energy
Revenue earned
Revenue earned from the REFABB grant	$ 1,640
Percentage of total revenue	30.00%
Customer one
Revenue earned
Percentage of total revenue	13.00%
Customer two
Revenue earned
Percentage of total revenue	12.00%
Customer three
Revenue earned
Percentage of total revenue	11.00%