| Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
| Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | |
| Income Tax [Line Items] | |||||
| Income tax expense | $ 104 | $ 109 | $ 395 | $ 266 | |
| Ireland | |||||
| Income Tax [Line Items] | |||||
| Net operating loss carryforwards | $ 23,265 | $ 23,265 | $ 13,648 | ||
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- Definition Income tax. No definition available. 
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Details 
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