Stockholders' Equity - Summary of Outstanding Warrant (Detail) (USD $)		3 Months Ended																																																																0 Months Ended			0 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 October 2006		Mar. 31, 2013 June 22, 2007		Mar. 31, 2013 August 25, 2008		Mar. 31, 2013 August 3, 2009		Mar. 31, 2013 September 4, 2009		Mar. 31, 2013 April 30, 2010 through July 1, 2010 Minimum	Mar. 31, 2013 April 30, 2010 through July 1, 2010 Maximum	Mar. 31, 2013 July 22, 2010		Mar. 31, 2013 October 13, 2010 and October 19, 2010 Minimum	Mar. 31, 2013 October 13, 2010 and October 19, 2010 Maximum	Mar. 31, 2013 January 3, 2011		Mar. 31, 2013 January 12, 2011		Mar. 31, 2013 February 18, 2011		Mar. 31, 2013 February 18, 2011; Series B Series B		Mar. 31, 2013 May 9, 2011		Mar. 31, 2013 May 20, 2011		Mar. 31, 2013 June 15, 2011, first issue		Mar. 31, 2013 June 15, 2011, second issue		Mar. 31, 2013 June 15, 2011, third issue		Mar. 31, 2013 June 20, 2011, first issue		Mar. 31, 2013 June 20, 2011, second issue		Mar. 31, 2013 July 6, 2011		Mar. 31, 2013 August 23, 2011		Mar. 31, 2013 September 29, 2011		Mar. 31, 2013 October 12, 2011		Mar. 31, 2013 October 17, 2011 through October 21, 2011 Minimum	Mar. 31, 2013 October 17, 2011 through October 21, 2011 Maximum	Mar. 31, 2013 November 2, 2011		Mar. 31, 2013 December 21, 2011		Mar. 31, 2013 January 19, 2012		Mar. 31, 2013 March 20, 2012; Series B Series B		Mar. 31, 2013 March 21, 2012; Series B Series B		Mar. 31, 2013 May 3,2012; Series B Series B		Mar. 31, 2013 June 4, 2012; Series B Series B		Mar. 31, 2013 May 8, 2012 Maximum		Mar. 31, 2013 May 7, 2012 Minimum		Mar. 31, 2013 May 7, 2012 Maximum		Mar. 31, 2013 June 22, 2012		Mar. 31, 2013 June 28, 2012		Mar. 31, 2013 July 25, 2012		Mar. 31, 2013 January 2013		Jan. 24, 2013 January 2013 Bridge Notes	May 15, 2013 Subsequent Event October 2006	Mar. 31, 2013 Subsequent Event October 2006	Jan. 24, 2013 Subsequent Event January 2013 Bridge Notes	Jan. 24, 2013 Subsequent Event January 2013 Bridge Notes Maximum
Warranty Liability [Line Items]
Percentage of Purchase Price Each Warrant Entitle Investor to Purchase																																																																														100.00%
Expiration Date		Apr. 27, 2014	[1]	Dec. 22, 2014	[2]	Aug. 25, 2015	[3]	Aug. 03, 2014	[2]	Sep. 04, 2014	[2]	Apr. 30, 2015	Jul. 01, 2015	Jul. 22, 2013	[2]	Oct. 13, 2015	Oct. 19, 2015	Feb. 18, 2014	[2]	Jan. 12, 2014	[2]	Feb. 18, 2016	[2]	Feb. 18, 2016	[2]	May 08, 2014	[2]	May 19, 2014	[2]	Jun. 15, 2016	[2]	Jun. 15, 2018	[2]	Jun. 15, 2018	[2]	Jun. 20, 2016	[2]	Jun. 20, 2018	[2]	Jul. 06, 2016	[2]	Aug. 23, 2016	[2]	Sep. 29, 2016	[3]	Oct. 12, 2016	[3]	Oct. 17, 2016	Oct. 21, 2016	Nov. 02, 2014	[2]	Dec. 21, 2016	[2]	Jan. 19, 2017	[2]	Mar. 20, 2017	[2]	Mar. 21, 2017	[2]	May 03, 2017	[2]	Jun. 04, 2017	[2]	May 07, 2013	[2]	May 07, 2019	[2]	May 08, 2019	[2]	Jun. 22, 2017	[2]	Jun. 28, 2017	[2]	Jul. 25, 2017	[2]	Jul. 25, 2018	[4]
Shares Subject to Outstanding Warrants	$ 41,032,048	$ 4,563,640		$ 257,583		$ 1,398,964		$ 32,005		$ 83,476		$ 222,217		$ 96,859		$ 36,197		$ 277,777		$ 131,892		$ 759,370		$ 393,933		$ 78,455		$ 90,313		$ 1,445,862		$ 45,000		$ 120,271		$ 57,079		$ 132		$ 419,729		$ 115,000		$ 550,703		$ 564,348		$ 76,555		$ 540,000		$ 6,315,789		$ 132,750		$ 5,244,000		$ 6,624,000		$ 110,450		$ 204,450		$ 917,839		$ 555,556		$ 200,000		$ 4,029,851		$ 719,178		$ 2,075,825		$ 1,545,000			$ 5,602,879	$ 4,563,639
Exercise Price at End of Period	3.90	0.62		41.80		38.60		17.00		17.00		18.20		18.20		13.40		9.00		9.20		6.57		6.00		2.92		2.92		3.85		3.12		3.85						3.85		3.85		0.83		0.83		2.64		2.12		1.22		1.22		1.02		1.02		1.02		1.02		2.12		0.90		0.90		0.85		0.85		0.89		1.00			0.51	0.62
Unit Purchase Price Each Warrant Entitle Investor to Purchase																																																																														$ 1.00			$ 1.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights																																																																														1,500,000
Class of Warrant or Right, Term																																																																														5 years 6 months
Class of Warrant or Right, Floor Price																																																																														$ 0.71
Class of Warrant or Right, Price Above Consolidated Closing Bid Price to Adjust Initial Exercise Price for Additional Warrants																																																																																	$ 0.01
Class of Warrant or Right, Number of Securities Underlying Additional Warrants																																																																														500,000				500,000
Class of Warrant or Right, Price Above Consolidated Closing Bid Price to Adjust Exercise Price																																																																																	$ 0.01
Class of Warrant or Right, Amount of Common Stock to Purchase of Warrant Issued to Private Placement Agent																																																																																	45,000

[1] Yes; contract provides for reset of exercise price along with increase in number of shares in connection with sales of future equity below current exercise price

[2] No; contract does not provide for an exercise price reset provision.

[3] Yes; contract provides for a price reset provision; however, provision is no longer applicable.

[4] Yes; contract provides for reset of exercise price under certain conditions, subject to a floor of $0.71; contract also provides for the issuance of additional warrants to purchase up to 500,000 shares of common stock if the remaining principal on the January 2013 Bridge Notes is not paid in full on or before July 1, 2013.