Warrants and Derivative Liabilities - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended		3 Months Ended		6 Months Ended		9 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended		0 Months Ended	3 Months Ended		6 Months Ended		9 Months Ended	0 Months Ended		6 Months Ended	0 Months Ended				1 Months Ended		0 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	0 Months Ended		3 Months Ended	6 Months Ended
	Nov. 15, 2013	Jun. 05, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2013 Convertible Bond	Sep. 30, 2013 Convertible Bond	Sep. 30, 2014 Senior Secured Term Loan First Warrant	Sep. 30, 2013 Senior Secured Term Loan First Warrant	Sep. 30, 2014 Senior Secured Term Loan First Warrant	Sep. 30, 2013 Senior Secured Term Loan First Warrant	Mar. 02, 2014 Capital Ventures International	Sep. 30, 2014 Capital Ventures International	Sep. 30, 2013 Capital Ventures International	Sep. 30, 2014 Capital Ventures International	Sep. 30, 2013 Capital Ventures International	Dec. 31, 2013 Capital Ventures International	Oct. 09, 2013 Senior Convertible Debt Capital Ventures International	Apr. 04, 2012 Senior Convertible Debt Capital Ventures International	Sep. 30, 2014 Senior Convertible Debt Capital Ventures International	Mar. 02, 2014 New Unsecured Senior Convertible Note	Dec. 31, 2013 New Unsecured Senior Convertible Note	Dec. 31, 2012 New Unsecured Senior Convertible Note	Apr. 04, 2012 New Unsecured Senior Convertible Note	Dec. 31, 2012 New Unsecured Senior Convertible Note Capital Ventures International Minimum	Dec. 31, 2012 New Unsecured Senior Convertible Note Capital Ventures International Maximum	Nov. 15, 2013 Senior Secured Loan	Sep. 30, 2014 Senior Secured Loan	Sep. 30, 2014 Senior Secured Loan Maximum	Sep. 30, 2014 Senior Secured Loan Maximum	Nov. 15, 2013 Senior Secured Loan Hercules Technology Growth Capital	Jun. 05, 2012 Senior Secured Loan Hercules Technology Growth Capital	Dec. 31, 2013 Senior Secured Loan Hercules Technology Growth Capital	Sep. 30, 2014 Senior Secured Loan Hercules Technology Growth Capital
Derivative [Line Items]
Number of shares received from warrants received to purchase common stock																					3,094,060								256,410				256,410	139,276
Warrant exercise, waiting period																			6 months
Warrant exercise period																			5 years
Exercise price																				$ 2.61	$ 5.45	$ 2.55							$ 1.95	$ 1.94			$ 1.95	$ 3.59	$ 1.95	$ 1.94
Beneficial ownership limitation percentage																											4.99%	9.99%
Required notification period																			61 days
Gain (loss) in change of fair value of derivative instruments and warrants			$ 795	$ 886	$ 760	$ 1,355		$ 300	$ 300	$ 0	$ 0	$ 0	$ 0		$ 800	$ 500	$ 700	$ 900													$ 100	$ 100
Conversion price																					$ 4.85			$ 3.10	$ 3.19	$ 4.85
Debt conversion, shares issued														6,600,000									6,600,000
Convertible debt instrument redemption waiting period							1 year
Convertible debt instrument contractual term							30 months
Warrants expiration date	May 15, 2019	Dec. 05, 2017