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Income Taxes - Narrative (Detail) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Income Tax Disclosure [Abstract] |  |  |  |  |
Income tax expense (benefit) | $ 6,496,980 | $ 7,700,732 | $ 19,018,708 | $ 18,497,315 |
Effective tax rate | 33.10% | 36.00% | 32.60% | 36.10% |
Federal statutory income tax rate, percent | 35.00% | 35.00% | 35.00% | 35.00% |
Effective income tax rate reconciliation, share-based compensation, excess tax benefit (tax shortfall), Amount | $ 400,000 |  | $ 1,700,000 |  |
Effective income tax rate reconciliation, tax benefit due to donation of appreciated securities, Amount |  |  |  | $ 100,000 |
Income tax effects allocated directly to equity |  | $ (200,000) |  | $ (5,600,000) |
Valuation allowance | $ 0 |  | $ 0 |  | $ 0

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- Definition Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit (Tax Shortfall), Amount + References No definition available. + Details
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- Definition Effective Income Tax Rate Reconciliation, Tax Benefit Due To Donation Of Appreciated Securities, Amount + References No definition available. + Details
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- Definition 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 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e39076-109324 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32672-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d),(e) -URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e38679-109324 + Details
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