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Contributed equity - Summary of Information about Shares Reserved for Employee Share Plans (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Employee Share Plans [Member]      
Disclosure of classes of share capital [line items]      
Beginning balance, shares 1,819,744 1,766,099 1,985,306
Beginning balance $ (30) $ (23) $ (39)
Purchases during the year, shares 2,232,589 2,683,469 2,242,345
Purchases during the year $ (45) $ (47) $ (32)
Vested/allocated during the year, shares (2,178,556)    
Vested/allocated during the year $ 37    
Vested during the year, shares   (2,629,824) (2,461,552)
Vested during the year   $ 40 $ 48
Ending balance, shares 1,873,777 1,819,744 1,766,099
Ending balance $ (38) $ (30) $ (23)
Dividend Reinvestment Plan [Member]      
Disclosure of classes of share capital [line items]      
Beginning balance, shares 0    
Beginning balance $ 0    
Purchases during the year, shares 6,823,092    
Purchases during the year $ (144)    
Vested/allocated during the year, shares (6,823,092)    
Vested/allocated during the year $ 144    
Ending balance, shares 0 0  
Ending balance $ 0 $ 0