Warrants and Warrant Liabilities - Additional Information (Detail) (USD $)	1 Months Ended					12 Months Ended			150 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	12 Months Ended		1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended				1 Months Ended
	Mar. 28, 2012	Dec. 30, 2010	Jul. 02, 2008	Feb. 04, 2008	May 31, 2003	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2002	Dec. 31, 2012	Aug. 31, 2001	Dec. 31, 2012 Minimum	Dec. 31, 2012 Maximum	Dec. 31, 2008 Adoption of New Accounting Pronouncement Effect	May 31, 2009 Warrant 8	Dec. 31, 2010 Warrant 8	May 31, 2010 Warrant Eleven First Issuance	Dec. 31, 2010 Warrant Eleven First Issuance	May 31, 2010 Warrant Eleven Second Issuance	Dec. 31, 2011 Warrant Eleven Second Issuance	Dec. 31, 2010 Warrant Eleven Second Issuance	Dec. 31, 2011 Warrant Eleven Second Issuance Minimum	Dec. 31, 2010 Warrant Eleven Second Issuance Minimum	Dec. 31, 2011 Warrant Eleven Second Issuance Maximum	Dec. 31, 2010 Warrant Eleven Second Issuance Maximum	Oct. 31, 2010 Warrant Twelve	Dec. 31, 2011 Warrant Twelve	Dec. 31, 2010 Warrant Twelve	Dec. 31, 2010 Warrant Thirteen First Issuance	Dec. 31, 2010 Warrant Thirteen First Issuance	Dec. 31, 2010 Warrant Thirteen Second Issuance	Apr. 30, 2009 Warrant 7	Dec. 31, 2011 Warrant 7	Dec. 31, 2010 Warrant 7	Dec. 31, 2010 Warrant 7 Vesting Scenario One	Dec. 31, 2010 Warrant 7 Vesting Scenario Two	May 31, 2008 Investor Relations Group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued in period	46,378	500	50,000	1,400	18,269			18,334																												6,500
Value of warrants														$ 232,000		$ 134,000		$ 40,000										$ 112,000		$ 2,000	$ 32,000	$ 104,000		$ 16,000	$ 124,000	$ 3,000
Exercise price of warrant		7.20	6.00	9.00	32.40			21.00		39.00				3.00		4.50		15.00							4.26			3.90	3.90	7.20	3.00					3.00
Warrants exercise period																																				3 years
Warrants to purchase shares of common stock														95,834		35,001		12,000							100,000			33,334	33,334	500	55,000
Vested warrant														74,000	74,000				7,500						25,000						13,334			8,334
Warrant that will vest upon the achievement of certain milestones																									50,000						41,666				33,332
Expected life						5 years 9 months 22 days	5 years 1 month 17 days		5 years 2 months 9 days		5 years	10 years		5 years		4 years		4 years			2 years 11 months 27 days	3 years 4 months 24 days	3 years 3 months 26 days	3 years 11 months 27 days	4 years 3 months 11 days			5 years		5 years	4 years	1 year 3 months 15 days		3 years 22 days	2 years 3 months 15 days
Expected volatility of the underlying stock						116.00%	131.00%		119.00%					124.00%		143.00%		143.00%			128.00%	130.00%	130.00%	144.00%	135.00%			130.00%		130.00%	134.00%	70.00%		140.00%	141.00%
Risk free interest rate						0.90%	1.90%		1.84%					2.16%		1.61%		1.61%			0.79%	0.51%	1.29%	1.68%	1.705%			1.90%		2.06%	1.76%	0.12%		1.69%	0.61%
Expected dividend rate						0.00%	0.00%		0.00%					0.00%		0.00%		0.00%	0.00%	0.00%					0.00%			0.00%		0.00%	0.00%	0.00%		0.00%	0.00%
Stock-based compensation expense						2,792,000	3,245,000		12,374,000						53,000		134,000		12,000	15,000						340,000	219,000		112,000				111,000
Reversal of stock-based compensation expense						100,000																										13,000
Forfeited warrant						616,726	141,084							21,834	21,834				4,500
Warrant vesting per month																		500
Warrant expected to vest in one year																									25,000
Warrants issued													1,164,929
Decrease in additional paid-in-capital													458,000
Increase in warrant liabilities													204,000
Change in fair value of warrant liabilities							$ (524,000)		$ 9,022,000