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Goodwill - Summary of goodwill (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Disclosure of reconciliation of changes in goodwill [Line Items]    
Goodwill at beginning of period $ 912 $ 1,037
Adjustment on currency translation 10 (125)
Goodwill at end of period 922 912
Cost [Member]    
Disclosure of reconciliation of changes in goodwill [Line Items]    
Goodwill at beginning of period 15,861 17,942
Goodwill at end of period 16,926 15,861
Accumulated impairment [Member]    
Disclosure of reconciliation of changes in goodwill [Line Items]    
Goodwill at beginning of period (14,949) (16,905)
Goodwill at end of period $ (16,004) $ (14,949)