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Retirement Plans - Schedule of Weighted-Average Assumptions Used to Determine Net Periodic Cost (Detail) - Plans Net Periodic Cost [Member] | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Net Periodic Benefit Cost Assumptions [Line Items] |  |  |
Discount rate | 3.61% | 4.01% | 3.31%
Health care cost trend: Initial | 6.50% | 6.75% | 7.00%
Health care cost trend: Ultimate | 4.75% | 4.75% | 4.75%
Year ultimate reached | 2022 | 2022 | 2022
Corridor | 10.00% | 10.00% | 10.00%
Recognition period for gains and losses | 11 years | 10 years | 11 years

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- Definition Defined Benefit Plan Corridor Rate + References No definition available. + Details
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- Definition Defined Benefit Plan Initial Health Care Cost Trend Rate + References No definition available. + Details
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- Definition Net Periodic Benefit Cost Assumptions [Line Items] + References No definition available. + Details
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- Definition The interest rate used to adjust for the time value of money. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The ultimate trend rate for health care costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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