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Warrants and Derivative Liabilities - Additional Information (Detail) (USD $) | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 0 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 0 Months Ended |  | 1 Months Ended | 6 Months Ended | 1 Months Ended | 0 Months Ended
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Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 Convertible Bond | Sep. 30, 2012 Convertible Bond | Sep. 30, 2013 Convertible Bond | Sep. 30, 2012 Convertible Bond | Sep. 30, 2013 Capital Ventures International | Sep. 30, 2012 Capital Ventures International | Sep. 30, 2013 Capital Ventures International | Sep. 30, 2012 Capital Ventures International | Oct. 09, 2013 Capital Ventures International Second Amendment | Sep. 30, 2013 Capital Ventures International Second Amendment Fourth Quarter 2013 | Sep. 30, 2013 Hercules Technology Growth Capital | Sep. 30, 2012 Hercules Technology Growth Capital | Sep. 30, 2013 Hercules Technology Growth Capital | Sep. 30, 2012 Hercules Technology Growth Capital | Apr. 04, 2012 Senior Convertible Debt Capital Ventures International | Apr. 04, 2010 Senior Convertible Debt Capital Ventures International | Dec. 31, 2012 New Unsecured Senior Convertible Note Capital Ventures International | Sep. 30, 2013 New Unsecured Senior Convertible Note Capital Ventures International | Dec. 31, 2012 New Unsecured Senior Convertible Note Capital Ventures International Minimum | Dec. 31, 2012 New Unsecured Senior Convertible Note Capital Ventures International Maximum | Jun. 05, 2012 Senior Secured Term Loan Hercules Technology Growth Capital
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares received from warrants received to purchase common stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,094,060 |  |  |  |  |  | 139,276
Warrant exercise, waiting period |  |  |  |  |  |  |  |  |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |
Warrant exercise period |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exercise price |  |  |  |  |  |  |  |  |  |  |  |  | $ 2.61 |  |  |  |  |  | $ 5.45 |  |  |  |  |  | $ 3.59
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 | $ 886,000 | $ 3,285,000 | $ 1,355,000 | $ 897,000 | $ 300,000 | $ 1,700,000 | $ 300,000 | $ 1,000,000 | $ 500,000 | $ 1,500,000 | $ 900,000 | $ 100,000 |  |  | $ 100,000 | $ 100,000 | $ 100,000 |  |  |  |  |  |  |  |
Conversion price |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4.85 |  |  | $ 3.19 | $ 4.85 |
Increase in derivative liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 500,000 | 500,000 |  |  |
Convertible debt instrument redemption waiting period |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Convertible debt instrument contractual term |  |  | 30 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-cash interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,100,000 |  |  |  |  |  |  |  |  |  |  |

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