U.S. Department of Energy Grant (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
U.S. Department of Energy Grant
Multi-year grant agreement amount			$ 6,000,000
Prorated cost-sharing obligation amount			3,900,000
Revenue recognized related to the multi-year grant agreement	$ 1,640,000	$ 1,578,000	$ 515,000