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Employee Benefits - Summary of Changes in Unrecognized Assets (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Disclosure of changes in unrecognized assets of defined benefit plans [abstract]      
Irrecoverable surplus impact at 1 January $ (31) $ (74) $ (77)
Interest expense (2) (4) (7)
Changes excluding amounts included in interest expense 1 47 9
Irrecoverable surplus impact at 31 December $ (32) $ (31) $ (74)