Financings - Additional Information (Detail) (USD $)	1 Months Ended																12 Months Ended						124 Months Ended			12 Months Ended	1 Months Ended					12 Months Ended	1 Months Ended			12 Months Ended					1 Months Ended	12 Months Ended	1 Months Ended								1 Months Ended
	Oct. 29, 2013	Jan. 20, 2012	Feb. 03, 2011	Jan. 12, 2011	May 27, 2010	Jun. 02, 2010	Dec. 04, 2009	Dec. 09, 2009	Sep. 15, 2009	Feb. 23, 2007 Y	May 03, 2006	Sep. 13, 2005	Jun. 06, 2005	Dec. 22, 2004 Y	Jan. 31, 2004	Sep. 30, 2003	Dec. 31, 2013 Y	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2009 Y	Dec. 31, 2005 Y	Dec. 31, 2004 Y	Dec. 31, 2013 Y	Apr. 26, 2006	Feb. 29, 2004	Dec. 31, 2009 J. P. Morgan Securities LLC	Feb. 23, 2007 Placement Agents	Feb. 23, 2007 Paramount	May 03, 2006 Paramount	Jan. 31, 2005 Paramount	Jun. 06, 2005 Series A Preferred Stock	Dec. 31, 2005 Series A Preferred Stock	May 27, 2010 Underwritten Public Offering	Feb. 23, 2007 Private Placement	May 03, 2006 Private Placement Y	Dec. 31, 2013 Private Placement Y	Dec. 31, 2009 Private Placement Y	Dec. 31, 2006 Private Placement	Jun. 06, 2005 Private Placement	May 31, 2005 Private Placement	Sep. 15, 2009 Private Placement Placement Agents	Dec. 31, 2009 Private Placement Placement Agents	Feb. 23, 2007 Investor	May 03, 2006 Investor Y	Feb. 23, 2007 Securities Offering	Sep. 13, 2005 Convertible Preferred Stock	Jun. 06, 2005 Convertible Preferred Stock	May 27, 2010 Maximum Underwritten Public Offering	Sep. 09, 2009 Maximum Private Placement	Sep. 09, 2009 Minimum Private Placement	Oct. 23, 2013 J.P. Morgan Securities Inc.	Oct. 29, 2013 J.P. Morgan Securities Inc.	Jan. 25, 2012 J.P. Morgan Securities Inc.	Jan. 31, 2012 J.P. Morgan Securities Inc.	Jan. 20, 2012 J.P. Morgan Securities Inc.	Jan. 31, 2012 J.P. Morgan Securities Inc. Total	Feb. 03, 2011 Barclays Capital Inc.	Feb. 08, 2011 Barclays Capital Inc.	Feb. 08, 2011 Barclays Capital Inc. Total
Long Term Debt And Equity Financings [Line Items]
Stock issued during period																																																			14,300,000	2,145,000	9,650,000	464,401		10,114,401			11,040,000
Issuance & sale of common stock in public offering price per share																																																			$ 3.50				$ 5.20		$ 5.75
Common stock, shares issued					30 days																																														30 days				30 days		30 days
Option to purchase common stock					1,050,000																																														2,145,000				1,447,500		1,440,000
Common stock price per share																																					$ 1.825	$ 4.63	$ 4.31	$ 4.75											$ 3.29				$ 4.888		$ 5.425
Net proceeds from issuance of common stock					$ 32,800,000		$ 45,200,000		$ 4,600,000																																											$ 53,900,000		$ 49,200,000				$ 59,800,000
Issuance & sale of common stock in public offering																																																							9,650,000		9,600,000
Common Stock Shares Sold	16,445,000	10,114,401	11,040,000	2,426,235	7,000,000	7,000,000	15,484,000	15,484,000	2,772,337	5,910,049	7,991,256																								7,991,256
Proceeds from issuance of common stock	57,600,000	52,600,000	63,500,000	11,600,000		35,000,000		48,000,000	5,100,000	30,900,000	37,000,000		18,100,000		4,500,000	500,000
Common stock price per share	$ 3.50	$ 5.20	$ 5.75	$ 4.80		$ 5.00	$ 3.10	$ 3.10	$ 1.825	$ 5.225	$ 4.63																						$ 5.00		$ 4.63
Common stock sdditional shares issued				3,636,926											9,017,538	1,001,949	100,159,618	83,236,840					100,159,618
Common stock par value per share				$ 0.001	$ 0.001												$ 0.001	$ 0.001			$ 0.001		$ 0.001	$ 0.001	$ 0.001
Research and development expense				17,500,000													42,852,000	83,446,000	57,083,000				255,197,000
Percentage of purchase commitment of securities offered																	19.99%
Percentage of net proceed offering																	40.00%
Aggregate purchase commitment amount																	50,000,000
Remaining maximum purchase commitment amount																	19,000,000						19,000,000
Issuance and sale of our common stock																																	7,000,000
Initial public offering price per share																																																$ 0.18
Underwriting discounts, commissions and other offering expenses					2,200,000
Gross proceeds from the offering							48,000,000
Payment of commissions and offering expenses							2,800,000
Warrants to purchase shares							0.5
Warrants to purchase an aggregate of shares of common stock											799,126			62,621			799,126			8,206,520	50,000	62,621							532,750					177,302	799,126		2,910,954				138,617	138,617	1,182,015	2,397,392
Warrants issued																										464,520
Exercise price per share										$ 5.75				$ 4.75			$ 5.09									$ 4.02			$ 5.09					$ 5.75			$ 2.04				$ 2.04
Exercisable period of warrants													7 years													6 months											5 years
Warrant term										5 years										5 years									7 years	7 years
Estimated fair value of warrant																	3,500,000			22,900,000			3,500,000											709,000	3,500,000		4,207,000						4,700,000	9,600,000
Expected volatility										93.00%	100.00%			134.00%			134.00%			105.00%	109.00%	134.00%	134.00%													100.00%	105.00%
Risk free interest										4.71%	5.01%			3.93%			3.93%			2.14%	4.39%	3.93%	3.93%														2.41%
Expected life										5				7			7			5	5	7	7												7	7	5							5
Expected dividend yield										0.00%	0.00%			0.00%			0.00%			0.00%	0.00%	0.00%	0.00%													0.00%	0.00%
Payment of placement agent fees									455,000
Cash penalty																																																	10.00%	1.00%
Total purchase price																																																	506,000
Term of warrant										5 years	5 years
Exercise price per share										$ 5.75
Percentage of additional shares issued by company										20.00%	30.00%
Cash commission paid										1,000,000	1,700,000						1,700,000										1,600,000	1,000,000								2,600,000									222,000
Term of warrant										5 years							7 years										5 years
Purchase of common stock										21,244																	156,058
Exercise price per share											$ 5.56																$ 5.75
Warrants issuable as a percentage of shares									5.00%								10.00%												10.00%	10.00%				3.00%
Risk free interest rate of warrants																	5.01%
Reimbursements made by company																	100,000
Percentage of common stock outstanding on fully diluted basis												96.80%
Payment made to affiliate												425,000
Issuance of series A convertible preferred stock																					15,077,000										4,197,946	15,077,000
Cash commission paid													7.00%
Warrant to purchase additional shares																																															419,794
Warrant exercise price as percent of market value													110.00%
Expenses to reimburse													50,000
Right of first refusal to act as the placement agent													3 years
Series A preferred stock was converted to common stock																																														4,197,946
Additional paid-in capital recorded using Black- Scholes model																	$ 1,700,000