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Income taxes - Summary tax losses carried forward (Detail)
$ in Millions
Dec. 31, 2021
USD ($)
2022 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses $ 407
2023 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 922
2024 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 1,614
2025 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 600
2026 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 496
2027 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses
2028 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 72
2029 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses 27
2030 [Member]  
Operating Loss Carryforwards [Line Items]  
Expiry date of unutilized tax losses $ 7