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Retirement Plans and Other Post-Retirement Benefits - Schedule of Health Care Cost Trend Rates Used in Calculating Benefit Obligations (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]    
Health care cost trend rate assumed for next year 6.80% 7.46%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.50% 4.50%
Year that the rate reaches the ultimate rate 2037 2028