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Equity - Summary of Fair Value of Options Estimated on Date of Grant Based on Weighted Average Assumptions (Detail)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield 0.00% 3.70%
Expected volatility 40.00% 29.00%
Risk-free interest rate 2.60% 2.10%