Common Stock (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 01, 2014	Jun. 01, 2014	Dec. 01, 2013	Jun. 01, 2013	Dec. 01, 2012	Jun. 01, 2012	Sep. 16, 2013	Sep. 16, 2013	Jun. 11, 2014	Dec. 18, 2013	Jul. 25, 2013	Apr. 23, 2013	Oct. 23, 2012	Aug. 08, 2012	Mar. 13, 2013
Common Stock
Net proceeds from issuance of common stock	$ 14,457,789	$ 11,706,066	$ 13,659,587
Exercise price of warrants (in dollars per share)	$ 0.91
Gross proceeds received from exercise of warrants	121,862	0	320,500
Value of shares issued to acquire a perpetual license under the agreement		500,000
Proceeds from employee stock option exercises	0	42,039	79,503
Issuance of shares upon exercise of employee stock options	0	12,983	22,800
Proceeds from employee stock purchase plans	158,334	263,599	666,095
Class A Common Stock | 2004 Employee Stock Purchase Plan
Common Stock
Share price (in dollars per share)				$ 0.8755	$ 0.9435	$ 0.9775	$ 1.29	$ 2.144	$ 3.40
Issuance of shares				67,206	105,454	93,916	132,970	89,571	139,480
Proceeds from employee stock purchase plans				58,839	99,495	91,803	171,796	191,862	474,233
Class A Common Stock | Stock Options
Common Stock
Proceeds from employee stock option exercises		42,039	79,503
Issuance of shares upon exercise of employee stock options		12,983	22,800
Exercise price of employee stock options exercised (in dollars per share)		$ 3.24
Class A Common Stock | EXO5
Common Stock
Number of shares issued to acquire a perpetual license under the agreement										372,578	372,578
Value of shares issued to acquire a perpetual license under the agreement										500,000	500,000
Class A Common Stock | Minimum | Stock Options
Common Stock
Exercise price of employee stock options exercised (in dollars per share)			$ 2.08
Class A Common Stock | Maximum | Stock Options
Common Stock
Exercise price of employee stock options exercised (in dollars per share)			$ 7.80
Class A Common Stock | Warrants - December 2013 financing - Subscribers
Common Stock
Exercise price of warrants (in dollars per share)	$ 0.91
Gross proceeds received from exercise of warrants	121,862
Issuance of shares upon exercise of warrants	133,914
Class A Common Stock | SRA Warrants - 2013 financing
Common Stock
Number of shares under warrants														72,268
Exercise price of warrants (in dollars per share)														$ 1.27
Class A Common Stock | Warrants Issued, March 2013
Common Stock
Number of shares under warrants																		150,603
Exercise price of warrants (in dollars per share)																		$ 3.32
Class A Common Stock | Warrants - 2012 and 2009 financing
Common Stock
Gross proceeds received from exercise of warrants			320,500
Issuance of shares upon exercise of warrants			145,000
Class A Common Stock | Warrants - 2012 and 2009 financing | Minimum
Common Stock
Exercise price of warrants (in dollars per share)			$ 2.20
Class A Common Stock | Warrants - 2012 and 2009 financing | Maximum
Common Stock
Exercise price of warrants (in dollars per share)			$ 2.32
Class A Common Stock | SRA Warrants - 2009 financing
Common Stock
Issuance of shares upon exercise of warrants			10,111
Class A Common Stock | At the market offerings through MLV
Common Stock
Number of shares sold	5,410,450	3,811,523	1,973,267
Net proceeds from issuance of common stock	5,383,009	5,352,893	9,053,593
Offering costs	172,000	177,000	290,000
Class A Common Stock | At the market offerings through MLV | Minimum
Common Stock
Share price (in dollars per share)	$ 0.90	$ 0.90	$ 2.60
Class A Common Stock | At the market offerings through MLV | Maximum
Common Stock
Share price (in dollars per share)	$ 1.39	$ 2.90	$ 9.12
Class A Common Stock | 2013 shelf registration statement
Common Stock
Number of shares sold												5,225,560
Share price (in dollars per share)												$ 1.90
Gross proceeds from issuance of common stock												9,928,564
Placement agent fees equal to gross proceeds from offering (as a percent)												7.00%
Net proceeds from issuance of common stock												9,075,000
Placement agent fees												695,000
Legal and other fees												159,000
Class A Common Stock | 2013 shelf registration statement | Warrants Issued, June 2014
Common Stock
Number of shares under warrants												2,090,224
Exercise price of warrants (in dollars per share)												$ 1.90
Class A Common Stock | 2013 shelf registration statement | Warrants - December 2013 financing - Subscribers
Common Stock
Number of shares sold													1,253,351
Share price (in dollars per share)													$ 0.9725
Gross proceeds from issuance of common stock													1,218,884
Placement agent fees equal to gross proceeds from offering (as a percent)													6.00%
Net proceeds from issuance of common stock													1,116,000
Placement agent fees													73,000
Legal and other fees													30,000
Number of shares under warrants													626,674
Exercise price of warrants (in dollars per share)													$ 0.91
Class A Common Stock | 2013 shelf registration statement | SRA Warrants - 2013 financing
Common Stock
Exercise price of warrants (in dollars per share)													$ 0.91
Class A Common Stock | 2013 shelf registration statement | SRA Warrants - 2013 financing | Maximum
Common Stock
Number of shares under warrants													75,201
Class A Common Stock | 2011 shelf registration statement
Common Stock
Number of shares sold														1,204,470	1,585,000	831,188	646,956
Share price (in dollars per share)														$ 1.27	$ 2.00	$ 4.01	$ 2.57
Gross proceeds from issuance of common stock														1,529,677	3,170,000	3,333,062	1,662,677
Placement agent fees equal to gross proceeds from offering (as a percent)														6.00%	6.00%
Net proceeds from issuance of common stock														1,408,000	2,920,000	3,073,000	1,533,000
Placement agent fees														92,000	190,200	199,984	99,761
Legal and other fees														30,000	60,000	60,000	30,000
Class A Common Stock | 2011 shelf registration statement | Warrants - April 2013 financing - Subscribers
Common Stock
Number of shares under warrants															792,500
Exercise price of warrants (in dollars per share)															$ 2.48
Class A Common Stock | 2011 shelf registration statement | Warrants - October 2012 financing
Common Stock
Number of shares under warrants																415,594
Exercise price of warrants (in dollars per share)																$ 3.76
Class A Common Stock | 2011 shelf registration statement | Warrants - August 2012 financing - Subscribers
Common Stock
Number of shares under warrants																	323,478
Exercise price of warrants (in dollars per share)																	$ 2.32
Class A Common Stock | 2011 shelf registration statement | Warrants - August 2012 financing - Placement Agent
Common Stock
Number of shares under warrants																	38,817
Exercise price of warrants (in dollars per share)																	$ 2.32
Class A Common Stock | Equity issuance
Common Stock
Number of shares sold																		301,205
Share price (in dollars per share)																		$ 3.32
Gross proceeds from issuance of common stock																		1,000,000
Placement agent fees equal to gross proceeds from offering (as a percent)																		6.00%
Net proceeds from issuance of common stock																		910,000
Placement agent fees																		60,000
Legal and other fees																		$ 30,000