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Schedule of Weighted Average Assumptions to Determine Pension Obligations (Detail) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
United States Pension Plans, Defined Benefit |  |  |
Defined Benefit Plan Disclosure |  |  |
Discount rate | 3.40% | 3.90% |
Salary progression rate | 2.30% | 2.60% |
Foreign Pension Plans, Defined Benefit |  |  |
Defined Benefit Plan Disclosure |  |  |
Discount rate | 1.80% | 1.80% |
Salary progression rate | 2.70% | 2.70% |
Postretirement Benefit Plans |  |  |
Defined Benefit Plan Disclosure |  |  |
Discount rate | 3.40% | 3.90% | 3.90%
Initial medical trend | 7.90% | 7.30% | 7.50%
Ultimate health care trend | 5.00% | 5.00% | 5.00%
Medical cost trend rate decrease to ultimate rate in year | 2026 | 2023 | 2023

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- Definition Defined benefit plan assumptions used calculating benefit obligation medical cost trend rate decrease to ultimate rate in year. + References No definition available. + Details
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- Definition Defined benefit plan assumptions used calculating benefit obligation salary progression rate. + References No definition available. + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + 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=82843861&loc=d3e1928-114920 + Details
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- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + 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=82843861&loc=d3e1928-114920 + Details
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