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Fair Value Measurements - Additional Information (Detail) - USD ($) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2017 | Jan. 31, 2013 | Dec. 31, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Contingent consideration obligations | $ 0 | $ 0 |  |  |  |
2012 Warrants |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Warrants issued to acquire Common Stock |  |  |  |  |  | 912,543
Warrants cancelled upon expiration |  |  |  | 143,811 |  |
2013 Warrants |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Warrants issued to acquire Common Stock |  |  |  |  | 833,530 |
Warrants outstanding | 0 |  |  |  |  |
Warrant |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Non-cash gain (loss) from change in fair value of the derivative liability | $ 432,141 | $ 870,760 | $ (293,072) |  |  |

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