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Australia Research and Development Tax Incentive - Additional Information (Detail) - Spero Potentiator Australia Pty Limited [Member] - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Australia [Member] |  |  |  |
Schedule Of Income Tax [Line Items] |  |  |  |
Tax incentive receivable | $ 1,900,000 |  | $ 1,900,000 | $ 100,000
Research and Development Expenses [Member] |  |  |  |
Schedule Of Income Tax [Line Items] |  |  |  |
Percentage of refundable tax incentive | 43.50% |  | 43.50% |
Reduction to research and development expenses | $ 100,000 | $ 0 | $ 1,800,000 | $ 100,000

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- Definition Effective Tax Incentive Rate Related To Research And Development + References No definition available. + Details
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