| Income Taxes - Summary of provision for income tax expense (Details 1) - USD ($) $ in Thousands | 12 Months Ended | |
|---|---|---|
| Dec. 31, 2018 | Dec. 31, 2017 | |
| Current | ||
| Federal | $ 0 | $ 0 | 
| State and local | 52 | 38 | 
| Foreign | 630 | 580 | 
| Total current income tax provision | 682 | 618 | 
| Deferred | ||
| Federal | 0 | 0 | 
| State and local | 0 | 0 | 
| Foreign | 31 | (18) | 
| Total deferred tax provision | 31 | (18) | 
| Total income tax provision | $ 713 | $ 600 | 
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- Definition Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of current foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- References No definition available. 
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- Definition Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of deferred foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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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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