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Benefit Plans - Assumptions Used in Estimating Fair Value of Granted Options and SARs and Results (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]      
Expected dividend yield 0.70% 0.60% 0.60%
Expected volatility 19.10% 16.90% 16.30%
Weighted average risk-free interest rate 1.50% 1.70% 1.10%
Expected holding period (in years) 5 years 5 years 5 years
Weighted average fair value of awards $ 6.94 $ 7.41 $ 6.75