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Investments - Additional Information (Detail) $ in Thousands | 9 Months Ended
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Sep. 30, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items] |
Unrealized net (losses) gains on available-for-sale securities | $ (329)
Certificates of Deposit [Member] |
Debt Securities, Available-for-sale [Line Items] |
Maturity period of investments | One year or less

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- Definition Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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