State research and development credit exchange receivable (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
State Research and Development Credit Exchange Receivable (Textual) [Abstract]
Percentage of credit exchange receivable	65.00%
Prepaid and other current assets under credit exchange program	$ 450,000	$ 0
Estimated amounts receivable under program	$ 293,000	$ 473,000