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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2018 | Sep. 30, 2011
Tax Credit Carryforward [Line Items] |  |
NOL allocated amount |  | $ 3,650,000
Afg [Member] |  |
Tax Credit Carryforward [Line Items] |  |
NOL allocated amount | $ 1,398,666 |
U. S. Federal Net Operating Tax [Member] |  |
Tax Credit Carryforward [Line Items] |  |
NOL allocated amount | $ 3,451,870 |
Minimum [Member] |  |
Tax Credit Carryforward [Line Items] |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029 |
Maximum [Member] |  |
Tax Credit Carryforward [Line Items] |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2032 |

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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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- Definition Expiration date of each operating loss carryforward included in operating loss carryforward, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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