Issuance of Common Stock (Details) (USD $)	9 Months Ended		0 Months Ended	3 Months Ended		3 Months Ended			9 Months Ended							0 Months Ended							0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jun. 02, 2013 Class A Common Stock 2004 Employee Stock Purchase Plan	Mar. 31, 2013 Class A Common Stock Stock Options	Mar. 13, 2013 Class A Common Stock Warrants Issued, March 2013	Sep. 30, 2013 Class A Common Stock At the market offerings through MLV	Jun. 30, 2013 Class A Common Stock At the market offerings through MLV	Mar. 31, 2013 Class A Common Stock At the market offerings through MLV	Sep. 30, 2013 Class A Common Stock At the market offerings through MLV	Sep. 30, 2013 Class A Common Stock At the market offerings through MLV Minimum	Jun. 30, 2013 Class A Common Stock At the market offerings through MLV Minimum	Mar. 31, 2013 Class A Common Stock At the market offerings through MLV Minimum	Sep. 30, 2013 Class A Common Stock At the market offerings through MLV Maximum	Jun. 30, 2013 Class A Common Stock At the market offerings through MLV Maximum	Mar. 31, 2013 Class A Common Stock At the market offerings through MLV Maximum	Sep. 19, 2013 Class A Common Stock At the market offerings through MLV Maximum Funding plan	Mar. 13, 2013 Class A Common Stock Equity issuance	Jul. 25, 2013 Class A Common Stock 2011 shelf registration statement	Apr. 23, 2013 Class A Common Stock 2011 shelf registration statement	Jul. 25, 2013 Class A Common Stock 2011 shelf registration statement Warrants - July 2013 financing - Subscribers	Apr. 23, 2013 Class A Common Stock 2011 shelf registration statement Warrants - April 2013 financing - Subscribers	Jun. 21, 2011 Common Stock 2011 shelf registration statement Funding plan	Sep. 16, 2013 EXO5 Class A Common Stock
Common Stock
Net proceeds from issuance of common stock	$ 9,389,626	$ 10,273,003				$ 2,508,576	$ 1,380,682	$ 262,945	$ 4,152,000								$ 910,000	$ 1,408,000	$ 2,920,000
Offering costs						84,000	45,000	8,700	138,000
Number of shares sold						1,862,360	840,581	94,988	2,797,929								301,205	1,204,470	1,585,000
Share price (in dollars per share)			$ 1.29							$ 1.00	$ 1.52	$ 2.80	$ 1.71	$ 2.68	$ 2.92		$ 3.32	$ 1.27	$ 2.00
Number of shares issued to acquire a perpetual license under the agreement																							372,578
Value of shares issued to acquire a perpetual license under the agreement	500,000																						500,000
Gross proceeds from issuance of common stock																15,000,000	1,000,000	1,529,677	3,170,000
Shelf registration statement, amount																						30,000,000
Placement agent fees equal to gross proceeds from offering (as a percent)																	6.00%	6.00%	6.00%
Placement agent fees																	60,000	92,000	190,200
Legal and other fees																	30,000	30,000	60,000
Number of shares under warrants					150,603															72,268	792,500
Exercise price of warrants (in dollars per share)					$ 3.32															$ 1.27	$ 2.48
Proceeds from employee stock option exercises	42,039	79,503		42,039
Issuance of shares upon exercise of employee stock options				12,983
Exercise price of employee stock options exercised (in dollars per share)				$ 3.24
Issuance of shares			132,970
Proceeds from employee stock purchase plan	$ 171,796	$ 474,233	$ 171,796