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Share-Based Compensation - Weighted-Average Assumptions for Estimating Fair Values (Detail)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Risk-free interest rate 1.80% 1.80% 2.80%
Dividend yield 1.60% 1.60% 1.60%
Expected life (years) 5 years 5 years 5 years
Expected volatility 42.00% 42.00% 40.00%