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Investments - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items] |  |
Loss in investment interest and other | $ 372 |
Unrealized gain or loss | 0 |
Unrealized net (losses) gains on available-for-sale securities | $ 0 | $ 255
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 of unrealized loss recognized in earnings from transfer of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) to investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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- Definition Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References No definition available. + Details
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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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