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Share Capital - Additional Information (Detail) - shares
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of classes of share capital [Line Items]      
Maximum percentage of preferred stock upon issuance or outstanding of common stock 20.00%    
Number of common shares authorized unlimited    
Shares outstanding 1,228,870,000 1,228,828,000 1,228,790,000
Preferred Shares [Member]      
Disclosure of classes of share capital [Line Items]      
Shares outstanding 0 0  
Stock Option Plan [Member]      
Disclosure of classes of share capital [Line Items]      
Shares available for future issuance 27,000,000 26,000,000