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Cash and cash equivalents - Additional information (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Disclosure of cash and cash equivalents [Line Items]    
Restricted cash and cash equivalents $ 295 $ 315
Repayment of third party borrowings 238 245
Subsidiaries    
Disclosure of cash and cash equivalents [Line Items]    
Restricted cash and cash equivalents 1,422 1,644
Repayment of third party borrowings $ 1,215 $ 1,442