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Benefit Plans - Summary of Fair Values for Stock-based Awards Granted Using Black-Scholes Option Pricing Model (Detail) - Black-Scholes Option Pricing Model [Member] - $ / shares
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average fair value of grants $ 2.35 $ 2.43 $ 5.31
Risk-free interest rate (range) - Based upon the U.S. Treasury Strip with a maturity date that approximates the expected term of the award, minimum 1.40% 1.20% 0.90%
Risk-free interest rate (range) - Based upon the U.S. Treasury Strip with a maturity date that approximates the expected term of the award, maximum 1.60% 1.40% 1.80%
Expected volatility (range) - Derived by using a 50/50 blend of implied and historical changes in the Company's historical stock prices over a time frame consistent with the expected life of the award, minimum 21.50% 24.70% 49.20%
Expected volatility (range) - Derived by using a 50/50 blend of implied and historical changes in the Company's historical stock prices over a time frame consistent with the expected life of the award, maximum 23.40% 28.50% 52.50%
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield (range) – Forecasted dividend yield based on the expected life 4.10% 4.50% 4.10%
Expected life (range) – Derived by referring to actual exercise experience 4 years 4 years 5 years
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield (range) – Forecasted dividend yield based on the expected life 4.30% 4.60% 4.50%
Expected life (range) – Derived by referring to actual exercise experience 5 years 5 years 6 years