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Investments - Schedule of Investment (Detail) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
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Investment [Line Items] |  |
Investments, at fair value | $ 6,711 | $ 6,756
Rabbi Trust Associated With Deferred Compensation Plan [Member] |  |
Investment [Line Items] |  |
Investments, at fair value | 6,689 | 6,734
Fair Value, Inputs, Level 1 [Member] | Investments in equity securities |  |
Investment [Line Items] |  |
Investments, at fair value | $ 22 | $ 22

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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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