Share-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation expense in stock compensation plans	$ 521,689	$ 602,380	$ 1,000,000	$ 1,200,000
Income tax benefit of stock compensation plans	109,555	210,833	218,897	420,068
Unrecognized compensation expense related to nonvested share-based compensation granted under the plan	1,800,000		$ 1,800,000
Weighted average period of unrecognized compensation expense			1 year 7 months 6 days
Cash from option exercises	0	652,027	$ 478,650.0	2,200,000
Tax benefit for tax deductions related to option exercises	$ 0	$ 70,822	$ 18,803	$ 178,356

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
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Unrecognized cost of unvested share-based compensation awards.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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