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Income Taxes - Narrative (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 3,702,100	$ 6,497,270
Effective tax rate	22.20%	33.10%
Federal statutory income tax rate, percent	21.00%	35.00%
Effective income tax rate reconciliation, share-based compensation, excess tax benefit (tax shortfall), Amount	$ 200,000	$ 400,000
Valuation allowance	$ 0		$ 0

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- Definition

Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit (Tax Shortfall), Amount

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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