Debt - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended								1 Months Ended										9 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 20, 2006	Sep. 30, 2013 Warrants, Exercise Price of $5.00 Per Share [Member]	Dec. 31, 2010 Series E- Redeemable Convertible Preferred Stock	Jul. 31, 2009 Series C-1 Preferred Stock	Feb. 28, 2009 Series C-1 Preferred Stock	Jan. 31, 2012 Series C-1 Preferred Stock As Amended	Mar. 31, 2008 First Issuance	Sep. 30, 2008 Second Issuance	Feb. 28, 2009 Third Issuance	Jul. 31, 2013 Third Issuance As Amended	Mar. 31, 2013 Third Issuance As Amended	Jan. 31, 2012 Third Issuance As Amended	Jul. 31, 2009 Fourth Issuance	Jul. 31, 2013 Fourth Issuance As Amended	Mar. 31, 2013 Fourth Issuance As Amended	Jan. 31, 2012 Fourth Issuance As Amended	Sep. 30, 2013 Facility Loan Agreement	Sep. 30, 2013 Facility Loan Agreement First Tranche	Sep. 30, 2013 Facility Loan Agreement Scenario one, conversion basis Second Tranche	Sep. 30, 2013 Facility Loan Agreement Wall Street Journal Prime Rate [Member] Scenario two Second Tranche
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 30,000,000																$ 10,000,000
Notes issued											3,500,000	10,500,000	7,000,000				6,700,000
Maturity date of debt											Mar. 17, 2011	Sep. 17, 2011	Feb. 28, 2012	Dec. 31, 2013	Aug. 01, 2013	Mar. 01, 2013	Jul. 31, 2012	Dec. 31, 2013	Aug. 01, 2013	Mar. 01, 2013
Facility loan, fixed interest rate											7.57%	7.57%	4.42%			4.919%	4.96%			5.46%		8.75%
Conversion price							$ 232.93	$ 438.84	$ 438.84	$ 292.56
Interest expense	200,000	200,000	600,000	600,000
Loan facility, outstanding principal and accrued interest settled			16,900,000
Loan facility extinguished in exchange of common stock			624,944
Facility loan, drawn			4,853,000																		5,000,000
Facility loan, fixed interest rate																							8.75%
Facility loan, interest amortization period																					36 months
Facility loan, final interest payment																					300,000
Facility loan, financial covenants																					Until positive Phase 2b data is achieved, the Company must be in compliance with one of two financial covenants at all times (1) maintain 1.3 times cash to outstanding debt or (2) maintain sufficient cash on hand to support eight months of operations based on a trailing average monthly cash burn.
Facility loan, prime rate plus																								4.25%
Facility fee																					1.00%
Warrants issued						121,739
Exercise price						5.00
Long term warrant liability	$ 5,310,000		$ 5,310,000			$ 500,000