| Furniture, Equipment and Leasehold Improvements, Net - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | |
|---|---|---|
| Mar. 31, 2017 | Mar. 31, 2016 | |
| Property Plant And Equipment Useful Life And Values [Abstract] | ||
| Depreciation expense | $ 208 | $ 179 | 
| X | ||||||||||
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- Definition Property plant and equipment useful life and values. No definition available. 
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| X | ||||||||||
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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://www.xbrl.org/2003/role/presentationRef 
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