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Stock-Based Compensation - Weighted Average Assumptions Used to Value Employee Stock Options Granted (Detail)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Expected option life 4 years 8 months 12 days 4 years 4 months 24 days 4 years 9 months 18 days
Expected volatility 18.40% 16.70% 18.40%
Expected dividend yield 2.90% 2.80% 3.60%
Risk-free interest rate 1.30% 1.40% 1.60%