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Weighted-Average Assumptions Used in Determining (Detail)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension benefits | United States And Puerto Rico Nonqualified Plans      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 3.62% 4.09%  
Rate of compensation increase 3.65% 3.75%  
Discount rate 4.09% 4.36% 4.00%
Expected return on plan assets 6.50% 7.00% 7.25%
Rate of compensation increase 3.75% 3.75% 3.76%
Pension benefits | International Unfunded Plans      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 2.02% 2.05%  
Rate of compensation increase 3.05% 3.08%  
Discount rate 2.03% 2.60% 2.26%
Expected return on plan assets 5.77% 6.07% 6.20%
Rate of compensation increase 3.11% 3.37% 3.33%
OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Annual rate of increase in the per-capita cost 6.25% 6.25%  
Rate decreased to 5.00% 5.00%  
by the year ended 2023 2022  
Annual rate of increase in the per-capita cost 6.25% 6.50% 6.00%
Rate decreased to 5.00% 5.00% 5.00%
by the year ended 2023 2022 2019
OPEB | United States And Puerto Rico Nonqualified Plans      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 3.51% 3.89%  
Discount rate 3.89% 4.12% 3.95%