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Marketable Securities - Additional Information (Detail) - USD ($) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2016
Investments Debt And Equity Securities [Abstract] |  |
Realized losses | $ 0 | $ 0
Investments other-than-temporarily impaired | $ 0 | $ 0
Investments maturity period | 2 years | 2 years

X
- Definition Investments maturity dates available for sale securities. + References No definition available. + Details
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- Definition Other than temporarily impaired investment. + References No definition available. + Details
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Balance Type: | debit
Period Type: | instant

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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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