| Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended | |
|---|---|---|---|
| Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | |
| Property Plant And Equipment [Abstract] | |||
| Depreciation expense | $ 113 | $ 99 | $ 136 | 
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- Definition The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. 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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