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Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions | 9 Months Ended |
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Sep. 30, 2017 | Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items] |  |
Number of highest-paid consecutive years for benefits | 5 years |
Defined benefit pension plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Minimum eligibility for full-time employees, age | 21 years |
Amount contributed to pension plan, expected in future |  | $ 2.1
Defined benefit pension plan | Minimum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Period of service credit by employee | 1 year |

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- Definition Defined benefit pension plan minimum eligible age of employee. + References No definition available. + Details
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- Definition Number of highest paid consecutive periods of service for calculation of average compensation related to benefits. + References No definition available. + Details
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- Definition Period of service credit by employee. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920 + Details
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- Details
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- Details
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