Warrants - Outstanding Warrants to Purchase Common Stock (Detail)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	6,108,050	6,132,050
Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	151,120	161,120
Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	5,956,930	5,970,930
Issued in June [Member] | Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	6,113	6,113
Warrant Exercise Price	22.50
Expiration Dates	Jun. 01, 2016
Issued in March [Member] | Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	4,209,357	4,209,357
Issued in March [Member] | Equity [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Warrant Exercise Price	7.50
Expiration Dates	Jun. 01, 2018
Issued in March [Member] | Equity [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Warrant Exercise Price	6.25
Expiration Dates	Oct. 01, 2015
Issued in August [Member] | Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	565,759	579,759
Warrant Exercise Price	18.75
Expiration Dates	Aug. 01, 2016
Series B Preferred Stock [Member] | Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	1,320	1,320
Warrant Exercise Price	2.50
Series B Preferred Stock [Member] | Warrant Liability [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	Nov. 01, 2015
Series B Preferred Stock [Member] | Warrant Liability [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	Jul. 01, 2015
Series D Preferred Stock [Member] | Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	29,800	39,800
Warrant Exercise Price	2.50
Series D Preferred Stock [Member] | Warrant Liability [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	Mar. 01, 2016
Series D Preferred Stock [Member] | Warrant Liability [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	Dec. 01, 2015
Placement Agent [Member] | Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	50,123	50,123
Warrant Exercise Price	13.75
Expiration Dates	Aug. 01, 2016
Series E Preferred Stock [Member] | Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	120,000	120,000
Warrant Exercise Price	2.50
Series E Preferred Stock [Member] | Warrant Liability [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	Jun. 01, 2017
Series E Preferred Stock [Member] | Warrant Liability [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Expiration Dates	May 01, 2017
Issued with Convertible Notes [Member] | Equity [Member]
Class of Warrant or Right [Line Items]
Warrants issued to purchase common stock	1,125,578	1,125,578
Warrant Exercise Price	2.50
Expiration Dates	Jun. 01, 2018