Warrants - Outstanding Warrants To Purchase Common Stock Warrants (Detail) - $ / shares		6 Months Ended
		Jun. 30, 2016	Jun. 15, 2016	Apr. 14, 2016	Jan. 30, 2015
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]
Number of Shares Underlying Warrants				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
Common Stock [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price					$ 6.96
Number of Shares Underlying Warrants		3,279,157
Common Stock [Member] | Class Of Warrant Or Right Issued on July 2006 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2006-07
Original Term		10 years
Exercise Price		$ 31.72
Number of Shares Underlying Warrants		17,656
Common Stock [Member] | Class Of Warrant Or Right Issued on November 2006 [Member]
Class Of Warrant Or Right [Line Items]
Issue Date		2006-11
Original Term		10 years
Exercise Price		$ 31.72
Number of Shares Underlying Warrants		1,576
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		$ 35.07
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		33,472
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] | 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	[1]	2016-04
Original Term	[1]	7 years
Exercise Price	[1]	$ 4.98
Number of Shares Underlying Warrants	[1]	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	[2]	2016-04
Original Term	[2]	5 years
Exercise Price	[2]	$ 3.99
Number of Shares Underlying Warrants	[2]	200,000
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	[3]	2016-06
Original Term	[3]	7 years
Exercise Price	[3]	$ 4.98
Number of Shares Underlying Warrants	[3]	1,002,507

[1] Issued on April 14, 2016 in connection with Private Placement to certain accredited investors.

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

[3] Issued on June 15, 2016 in connection with the Subsequent Financing.