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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) |  | 3 Months Ended
--- | --- | ---
Jan. 01, 2018 | Mar. 31, 2018 | Mar. 31, 2017
Summary Of Significant Accounting Policies [Line Items] |  |  |
Revenue recognition under milestone method |  | $ 0 | $ 0
ASU 2014-09 [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Cumulative adjustment to retained earnings and accounts receivable | $ 2,900,000 |  |
JGB Debt [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Restricted cash released upon full conversion of debt obligation |  | $ 9,400,000 |
JGB Debt [Member] | ASU 2017-11 [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Reclassification of warrant liability to equity | $ 6,600,000 |  |
Allenex [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Acquisition date |  | Apr. 14, 2016 |
Allenex [Member] | Maximum [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Company ownership percentage |  | 100.00% |

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