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Warrants and Derivative Liabilities - Additional Information (Detail) $ / shares in Units, $ in Thousands |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 19, 2014 $ / shares shares | Apr. 04, 2012 shares | Oct. 31, 2013 $ / shares | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Apr. 29, 2015 $ / shares | Nov. 13, 2014 shares / pure $ / shares shares
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Gain (loss) in change of fair value of derivative instruments and warrants (less than $0.1 million for three months ended 2015) | $ |  |  |  | $ 1,244 | $ 701 | $ 567 | $ 1,501 |  |
Sale of stock, price per share (in dollars per share) |  |  |  |  |  |  |  | $ 6.00 |
Hercules Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Gain (loss) in change of fair value of derivative instruments and warrants (less than $0.1 million for three months ended 2015) | $ |  |  |  | 100 | 100 | 100 | 100 |  |
November 2014 Warrant |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Warrant exercise price (in dollars per share) |  |  |  |  |  |  |  | 9.41 |
Gain (loss) in change of fair value of derivative instruments and warrants (less than $0.1 million for three months ended 2015) | $ |  |  |  | 900 | 500 | $ 300 | 1,200 |  |
Warrants expiration date |  |  |  |  |  | Nov. 13, 2019 |  |  |
Common stock units offered (in shares) | shares |  |  |  |  |  |  |  |  | 909,090
Warrants to purchase one share of common stock |  |  |  |  |  |  |  |  | 0.9
Number of warrants issued to purchase common stock (in shares) | shares |  |  |  |  |  |  |  |  | 818,181
Sale of stock, price per share (in dollars per share) |  |  |  |  |  |  |  |  | $ 11.00
Capital Ventures International | Exchanged Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Gain (loss) in change of fair value of derivative instruments and warrants (less than $0.1 million for three months ended 2015) | $ |  |  |  | $ 200 | $ 100 | $ 200 | $ 200 |  |
Senior Convertible Note warrant | Capital Ventures International | Original Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Number of shares received from warrants received to purchase common stock (in shares) | shares |  | 309,406 |  |  |  |  |  |  |
Senior Convertible Note warrant | Capital Ventures International | Exchanged Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Warrant exercise, waiting period |  |  | 6 months |  |  |  |  |  |
Warrant exercise period |  |  | 5 years |  |  |  |  |  |
Warrant exercise price (in dollars per share) |  |  | $ 15.94 |  |  |  |  |  |
Senior Convertible Note warrant | Capital Ventures International | Maximum | Exchanged Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Beneficial ownership limitation percentage |  |  | 4.99% |  |  |  |  |  |
Beneficial ownership, limitation option, percentage |  |  | 9.99% |  |  |  |  |  |
Required notification period |  |  | 61 days |  |  |  |  |  |
Senior Secured Loan | Hercules Technology Growth Capital | Hercules Warrants |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |
Number of shares received from warrants received to purchase common stock (in shares) | shares | 58,823 |  |  |  |  |  |  |  |
Warrant exercise price (in dollars per share) | $ 11.00 |  |  |  |  |  |  | $ 9.41 |
Warrants expiration date |  |  |  |  |  | Jun. 30, 2020 |  |  |

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