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Income Taxes - Summary of Activity in Total Valuation Allowances (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Income Tax Disclosure [Abstract] |  |  |
Balance at Beginning of Year | $ 4,090 | $ 2,376 |
Additions | 3,518 | 1,882 | $ 2,376
Recoveries |  | (168) |
Reprice | 0 | 0 | 0
Balance at End of Year | $ 7,608 | $ 4,090 | $ 2,376

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- Definition Deferred tax assets valuation recoveries. + 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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