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Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
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Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |
Short-term investments - trading securities | $ 3,302 | $ 681
Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |
Short-term investments - trading securities | 695 | $ 681
Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |
Short-term investments - trading securities | $ 2,607 |

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- Definition Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] + References No definition available. + Details
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- Definition Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 + Details
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