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Income Taxes - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($)
Operating Loss Carryforwards [Line Items] |
Increase (decrease) in valuation allowance | $ 41.0
Federal research and development credits expiration year start | 2038
Decrease in deferred tax asset | $ 0.8
Unrecognized tax benefits that would not impact effective tax rate | 2.6
Orphan Drug Credit |
Operating Loss Carryforwards [Line Items] |
Research and development credit | $ 9.6
Maximum |
Operating Loss Carryforwards [Line Items] |
Net operating losses carryforward available to offset future federal taxable income , percentage | 80.00%
Federal |
Operating Loss Carryforwards [Line Items] |
Net operating losses (“NOL”) carryforwards | $ 175.8
Net operating loss carry forwards expiration year start | 2034
Net operating losses (“NOL”) that can be carried forward indefinitely | $ 172.9
Research and development credit | 9.6
California |
Operating Loss Carryforwards [Line Items] |
Net operating losses (“NOL”) carryforwards | $ 1.1
Net operating loss carry forwards expiration year start | 2036
Research and development credit | $ 2.7
Irish |
Operating Loss Carryforwards [Line Items] |
Net operating losses (“NOL”) carryforwards | $ 53.0

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