Warrants and Derivative Liabilities - Additional Information (Detail) - USD ($)								1 Months Ended	3 Months Ended
	Apr. 29, 2015	Dec. 19, 2014	Nov. 13, 2014	Nov. 15, 2013	Oct. 09, 2013	Jun. 05, 2012	Apr. 04, 2012	Dec. 31, 2012	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Exercise price	$ 9.41
Warrants to purchase one share of common stock			90.00%
Gain (loss) in change of fair value of derivative instruments and warrants									$ 800,000		$ (35,000)
Warrants expiration date			Nov. 13, 2019	May 15, 2019		Dec. 05, 2017
Common stock units offered			909,090
Number of warrants issued to purchase common stock			818,181
Shares issued, price per share			$ 11.00
Senior Secured Term Loan First Warrant
Derivative [Line Items]
Gain (loss) in change of fair value of derivative instruments and warrants											0
Hudson Warrant
Derivative [Line Items]
Gain (loss) in change of fair value of derivative instruments and warrants									700,000
Maximum | Senior Secured Term Loan New Warrant
Derivative [Line Items]
Gain (loss) in change of fair value of derivative instruments and warrants									$ 100,000
Capital Ventures International
Derivative [Line Items]
Warrant exercise, waiting period									6 months
Warrant exercise period									5 years
Common stock, shares issued										909,090
Warrants to purchase one share of common stock										90.00%
Required notification period									61 days
Gain (loss) in change of fair value of derivative instruments and warrants									$ 100,000		(100,000)
Senior Convertible Debt | Capital Ventures International
Derivative [Line Items]
Number of shares received from warrants received to purchase common stock							309,406
Exercise price	15.94				$ 26.10		$ 54.50			$ 22.10
New Unsecured Senior Convertible Note | Capital Ventures International | Minimum
Derivative [Line Items]
Beneficial ownership limitation percentage								4.99%
New Unsecured Senior Convertible Note | Capital Ventures International | Maximum
Derivative [Line Items]
Beneficial ownership limitation percentage								9.99%
Senior Secured Loan
Derivative [Line Items]
Number of shares received from warrants received to purchase common stock				25,641
Exercise price			$ 17.00	$ 19.50
Common stock, shares issued			909,090
Warrants to purchase one share of common stock			90.00%
Senior Secured Loan | Maximum
Derivative [Line Items]
Gain (loss) in change of fair value of derivative instruments and warrants											$ 0
Senior Secured Loan | Hercules Technology Growth Capital
Derivative [Line Items]
Number of shares received from warrants received to purchase common stock		58,823				13,927
Exercise price	$ 9.41	$ 11.00	$ 17.00			$ 35.90						$ 19.50
Common stock, shares issued			909,090
Warrants to purchase one share of common stock			90.00%
Warrants expiration date		Jun. 30, 2020