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Employee Benefit Plans - Additional Information (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2017 USD ($)
Defined Benefit Pension Plans |
Defined Benefit Plan Disclosure [Line Items] |
Expected contribution | $ 15.1
OPEB |
Defined Benefit Plan Disclosure [Line Items] |
Expected contribution | $ 1.1

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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 the employer's best estimate of contributions expected to be paid to the plan in the current fiscal period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2709-114920 + Details
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