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Income Taxes - Narrative (Detail) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
Dec. 22, 2017 | Dec. 21, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Income Taxes [Line Items] |  |  |  |  |
Federal income tax at statutory rate | 21.00% | 35.00% | 35.00% | 35.00% | 35.00%
Percentage of tax position will realized or sustained upon examination |  |  | 50.00% |  |
Valuation allowance on deferred tax assets |  |  | $ 0 | $ 0 |
Unrecognized tax benefits |  |  | $ 0 | $ 0 |
Deferred tax asset, provisional income tax expense | $ 5,500,000 |  |  |  |
Minimum |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Percentage of tax position will realized or sustained upon examination |  |  | 50.00% |  |
Federal |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss carryovers |  |  | $ 6,000,000 |  |

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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 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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