Stock Based Compensation - Employee Stock Purchase Plan - Additional Information (Detail) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value | $ 15.81 | ||
| Employee Stock Purchase Plan [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value | $ 5.42 | $ 5.20 | $ 2.46 |
| Percentage of proportionate value of call option of stock | 85.00% | ||
| Percentage of proportionate value of put option of stock | 15.00% | ||
| Allocated share-based compensation expense | $ 331,913 | $ 318,735 | $ 113,217 |
| X | ||||||||||
- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition Percentage of proportionate value of call option for stock. No definition available.
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- Definition Percentage of proportionate value of put option for stock. No definition available.
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- Details
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