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Share-Based Compensation - Stock Options Assumptions Table (Detail) - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Weighted-average grant-date fair value (in usd per share) $ 15.36 $ 14.77 $ 15.92
Assumptions      
Expected option life—years 4 years 9 months 18 days 4 years 9 months 18 days 4 years 1 month 6 days
Volatility 33.50% 33.60% 38.20%
Risk-free interest rate 2.90% 2.00% 1.30%
Dividend yield 1.90% 0.40% 0.60%