Warrants - Outstanding Warrants To Purchase Common Stock Warrants (Detail) - $ / shares		6 Months Ended
		Jun. 30, 2017	Sep. 26, 2016	Sep. 25, 2016	Jun. 15, 2016	Apr. 14, 2016
Class Of Warrant Or Right [Line Items]
Number of Shares Underlying Warrants					1,002,507
Private Placement [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price			$ 4.00	$ 4.98
Number of Shares Underlying Warrants			1,775,580			1,975,580
Private Placement [Member] | Accredited Investors [Member]
Class Of Warrant Or Right [Line Items]
Number of Shares Underlying Warrants						1,775,580
Private Placement [Member] | Placement Agents [Member]
Class Of Warrant Or Right [Line Items]
Number of Shares Underlying Warrants						200,000
Subsequent Financing [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price			$ 4.00	4.98
Number of Shares Underlying Warrants			1,002,507
Common Stock [Member]
Class Of Warrant Or Right [Line Items]
Number of Shares Underlying Warrants		4,509,926
Common Stock [Member] | Class Of Warrant Or Right Issued on February 2008 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2008-02
Original Term		10 years
Exercise Price		$ 35.10
Number of Shares Underlying Warrants		22,792
Common Stock [Member] | Class Of Warrant Or Right Issued on August 2009 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2009-08
Original Term		10 years
Exercise Price		$ 21.78
Number of Shares Underlying Warrants		33,473
Common Stock [Member] | Class Of Warrant Or Right Issued on July 2010 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2010-07
Original Term		9 years
Exercise Price		$ 21.78
Number of Shares Underlying Warrants		6,694
Common Stock [Member] | Class Of Warrant Or Right Issued on December 2010 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2010-12
Original Term		7 years
Exercise Price		$ 21.78
Number of Shares Underlying Warrants		17,215
Common Stock [Member] | Class Of Warrant Or Right Issued on August 2012 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2012-08
Original Term		7 years
Exercise Price		$ 21.78
Number of Shares Underlying Warrants		167,182
Common Stock [Member] | Class Of Warrant Or Right Issued on January 2015 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2015-01
Original Term		5 years
Exercise Price		$ 6.96
Number of Shares Underlying Warrants		34,483
Common Stock [Member] | Class Of Warrant Or Right Issued on March 2017 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date	[1]	2017-03
Original Term	[1]	5 years
Exercise Price	[1]	$ 5.00
Number of Shares Underlying Warrants	[1]	1,250,000
Common Stock [Member] | Private Placement [Member] | Accredited Investors [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price			$ 4.00	4.98
Common Stock [Member] | Private Placement [Member] | Accredited Investors [Member] | Class Of Warrant Or Right Issued on April 2016 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date	[2]	2016-04
Original Term	[2]	7 years
Exercise Price	[2]	$ 4.00
Number of Shares Underlying Warrants	[2]	1,775,580
Common Stock [Member] | Private Placement [Member] | Placement Agents [Member] | Class Of Warrant Or Right Issued on April 2016 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date	[3]	2016-04
Original Term	[3]	5 years
Exercise Price	[3]	$ 3.99
Number of Shares Underlying Warrants	[3]	200,000
Common Stock [Member] | Subsequent Financing [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price			$ 4.00	$ 4.98
Common Stock [Member] | Subsequent Financing [Member] | Class Of Warrant Or Right Issued on June 2016 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date	[4]	2016-06
Original Term	[4]	7 years
Exercise Price	[4]	$ 4.00
Number of Shares Underlying Warrants	[4]	1,002,507

[1] Issued on March 15, 2017 in connection with the JGB Debt.

[2] Issued on April 14, 2016 in connection with the Private Placement to certain accredited investors. The exercise price was reset from $4.98 to $4.00 as a result of the Public Offering that closed on September 26, 2016. In accordance with the anti-dilution provisions, the exercise price of the warrants issued in connection with the Private Placement reset from $4.98 per share to $4.00 per share, which was the price paid by investors in the Public Offering, which closed on September 26, 2016.

[3] Issued on April 14, 2016 in connection with the Private Placement to placement agents.

[4] Issued on June 15, 2016 in connection with the Subsequent Financing. The exercise price was reset from $4.98 to $4.00 as a result of the Public Offering that closed on September 26, 2016. In accordance with the anti-dilution provisions, the exercise price of the warrants issued in connection with the Subsequent Financing reset from $4.98 per share to $4.00 per share, which was the price paid by investors in the Public Offering, which closed on September 26, 2016