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Schedule of Carrying Value of Trust Assets, Including Unrealized Gains or Losses (Detail) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
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Compensation And Retirement Disclosure [Abstract] |  |  |
Investments held in Rabbi Trust at fair value | [1] | $ 8,809 | $ 8,908
Unrealized gains (losses) in fair value of trust assets |  | (43) | 256
Obligations under the supplemental plan |  | $ 32,581 | $ 32,508
[1] | The company converted all investments held in the rabbi trust to cash to fund a lump sum benefit to the former CEO in May 2018. Refer to Note (6) for more information regarding this payment.

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- Definition Defined Benefit Plan Supplemental Plan Obligations + References No definition available. + Details
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- Definition Trust assets, carrying value, net + References No definition available. + Details
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- Definition Carrying amount as of the balance sheet date of assets held under deferred compensation agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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