Warrants to Purchase Common Stock - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended			90 Months Ended		1 Months Ended								12 Months Ended						1 Months Ended			12 Months Ended			12 Months Ended					12 Months Ended	1 Months Ended	0 Months Ended	12 Months Ended				12 Months Ended
	Aug. 31, 2012	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Aug. 16, 2012	Dec. 31, 2012 Non Employee Warrants [Member]	Aug. 31, 2012 Non Employee Warrants [Member]	Apr. 30, 2012 Non Employee Warrants [Member]	Dec. 31, 2011 Non Employee Warrants [Member]	Sep. 30, 2011 Non Employee Warrants [Member]	Mar. 31, 2011 Non Employee Warrants [Member]	Feb. 28, 2011 Non Employee Warrants [Member]	Nov. 30, 2010 Non Employee Warrants [Member]	Dec. 31, 2013 Non Employee Warrants [Member]	Dec. 18, 2012 Non Employee Warrants [Member]	Aug. 28, 2012 Non Employee Warrants [Member]	Aug. 16, 2012 Non Employee Warrants [Member]	Apr. 02, 2012 Non Employee Warrants [Member]	Nov. 22, 2010 Non Employee Warrants [Member]	Sep. 30, 2011 Non Employee Warrants [Member] Maximum [Member]	Sep. 30, 2011 Non Employee Warrants [Member] Minimum [Member]	Apr. 30, 2012 Warrants to Purchase Series C Shares [Member]	Dec. 31, 2013 Warrants to Purchase Series C Shares [Member]	Dec. 31, 2013 National Securities Corporation [Member]	Dec. 31, 2013 National Securities Corporation [Member] Warrants to Purchase Series C Shares [Member]	Dec. 31, 2013 Debt Placement Agent Warrants [Member]	Apr. 26, 2010 Debt Placement Agent Warrants [Member]	Apr. 26, 2010 Debt Placement Agent Warrants [Member] Series A [Member]	Apr. 26, 2010 Debt Placement Agent Warrants [Member] Senior Convertible Notes 2008 [Member] Series A [Member]	Apr. 26, 2010 Debt Placement Agent Warrants [Member] Senior Convertible Notes 2009 [Member] Series A [Member]	Dec. 31, 2007 Common Stock [Member]	Apr. 30, 2012 Common Stock [Member] Warrants to Purchase Series C Shares [Member]	Nov. 15, 2011 Common Stock [Member] Warrants to Purchase Series C Shares [Member]	Dec. 31, 2013 Common Stock [Member] Warrants to Purchase Series C Shares [Member]	Apr. 02, 2012 Common Stock [Member] Warrants to Purchase Series C Shares [Member]	Dec. 31, 2013 Preferred Stock Placement Warrants [Member]	Dec. 31, 2013 Preferred Stock Placement Warrants [Member] Series A [Member]	Dec. 31, 2013 Preferred Stock Placement Warrants [Member] Series A [Member] Maximum [Member]	Dec. 31, 2013 Preferred Stock Placement Warrants [Member] Series A [Member] Minimum [Member]	Dec. 31, 2009 PCP Warrants [Member]	Dec. 31, 2011 PCP Warrants [Member] Series A [Member]	Dec. 31, 2009 PCP Warrants [Member] Series A [Member]
Warrants To Purchase Common Stock [Line Items]
Period of Issued Warrants														5 years														7 years
Notes Principal Amount Percentage																												10.00%		10.00%												40.00%		40.00%
Warrant exercise price							5.72				6.00	2.95	1.37	1.37			4.88	5.65	5.72	1.37	9.23						5.59	1.00			9.23	9.23							8.39			1.00	6.15	9.23
Exercise price percentage																														110.00%														110.00%
Issued warrants to purchase common stock							20,000				5,000	75,000	60,000	50,000			35,000	73,009	25,000	25,000	41,716						461,263				48,510	41,716							258,421				40,787	27,175
Fair value of the warrant							$ 92,000				$ 19,100	$ 144,000	$ 98,000	$ 69,000			$ 103,000		$ 113,000		$ 38,000								$ 200,000		$ 100,000	$ 100,000						$ 600,000						$ 47,000
Volatility	104.51%							97.45%	110.30%		91.10%		95.40%	93.20%	93.70%							96.30%	90.80%												92.40%					94.40%	92.00%
Risk free rate	1.06%							0.28%	0.83%		0.40%		3.58%	2.65%	1.40%							0.90%	0.40%												0.93%					3.30%	2.00%
Estimated per share fair value																					$ 1.96														$ 8.00				$ 3.45
Dividend yield	0.00%							0.00%	0.00%		0.00%	0.00%	0.00%	0.00%
Fair Value Assumptions, Expected Term	6 years							3 years	5 years				10 years	5 years	5 years
Warrants issued																				20,970
Warrant Fair Value										$ 8.50
Stock Issued During Period Shares warrants Exercised																78,710																				78,636
Cashless Exercise Of Warrants																153,415																				328,510
Investment Warrants, Exercise Price																$ 5.00								$ 5.59												$ 5.45
Stock Issued During Period Shares New Issues		5,750,000	10,558,422	3,361																					340								2,125,096
Proceeds From Issuance Of Common Stock		26,400,000	92,399,000	28,855,000	193,000	121,452,000																														1,000
Class of Warrant or Right, Outstanding																																				711,895
Fee paid to National Securities Corporation as consideration for its services as the placement agent																										10.00%
Fair value of warrants reduction in carrying amount in share																										1,300,000
Amount Charge Due To Mark To Market Valuation Of Warrants Exercisable For Common Stock																																			1,400,000
Final fair value of common stock																																			$ 2,700,000
Common Stock Shares Issued			39,652,950	24,400,754		39,652,950																															534
Common Stock Shares Exercised																																		2,986
Fair market value of common stock on the date of exercise																								$ 6.81