Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 33,569,198	$ 47,743,155
Accounts receivable	2,281,282	2,046,219
Prepaid expenses	1,103,449	137,634
Total current assets	36,953,929	49,927,008
Restricted cash	404,850	404,850
Property and equipment, net	4,469,882	3,267,796
Other assets	147,246	147,246
Total assets	41,975,907	53,746,900
Current liabilities:
Accounts payable	1,798,228	3,739,125
Accrued expenses	939,811	1,237,025
Lease exit liability - current	1,229,454	628,768
Deferred revenue - current	21,298,318	24,123,176
Total current liabilities	25,265,811	29,728,094
Lease exit liability	8,378,184	9,445,171
Deferred rent liability	2,888,688	2,801,653
Preferred stock warrant liability	679,296	52,947
Deferred revenue, net of current portion	8,812,342	19,956,343
Total liabilities	46,024,321	61,984,208
Stockholders' equity (deficit):
Common stock, $0.01 par value - 425,000,000 shares authorized, 2,124,624 and 1,098,914 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively	21,246	10,989
Treasury stock, at cost; 14,381 shares at September 30, 2013 and December 31, 2012	(57,742)	(57,742)
Additional paid-in capital	165,569,134	164,334,646
Accumulated deficit	(172,528,254)	(175,472,403)
Total stockholders' equity (deficit)	(4,048,414)	(8,237,308)
Total liabilities and stockholders' equity (deficit)	41,975,907	53,746,900
Series A-1 Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	268,748	268,748
Series A-2 Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	73,646	73,646
Series B Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	714,012	714,012
Series C Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	1,109,522	1,109,522
Series D-1 Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	144,462	144,462
Series D-2 Convertible Preferred Stock [Member]
Stockholders' equity (deficit):
Convertible preferred stock	$ 636,812	$ 636,812