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Capital Stock - Schedule of Changes in Number of Common Shares Outstanding (Detail) - shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Class Of Stock [Line Items]      
Beginning balance 249,510,022 248,129,430 247,144,356
Restricted stock grants 1,186,290 865,095 539,096
Treasury shares issued   5,302 15,580
Treasury shares repurchased (1,798,468)    
Ending balance 249,630,803 249,510,022 248,129,430
Restricted Stock      
Class Of Stock [Line Items]      
Restricted stock units vested 720,212 434,046 344,937
Performance Share      
Class Of Stock [Line Items]      
Performance stock units issued 12,747 76,149 85,461