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Income Taxes - Narrative (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 6,497,270	$ 5,171,776
Effective tax rate	33.10%	35.80%
Federal statutory income tax rate, percent	35.00%	35.00%
Effective income tax rate reconciliation, share-based compensation, excess tax benefit (tax shortfall), Amount	$ 400,000
Effective income tax rate reconciliation, tax benefit due to donation of appreciated securities, Amount	100,000	$ 100,000
Valuation allowance	$ 0		$ 0
Income tax effects allocated directly to equity		$ (5,200,000)

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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.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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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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The sum of the tax effects of all items occurring during the period that have been charged or credited directly to other comprehensive income or to related components of shareholders' equity.

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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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