XML 459 R256.htm IDEA: XBRL DOCUMENT v3.10.0.1
Post-retirement benefits - Summary of movement in net defined benefit liability (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]      
Beginning balance $ (2,499) $ (2,542)  
Amounts recognised in Income statement (288) (245) $ (265)
Amounts recognised in Other comprehensive income 907 6 (90)
Contributions by employer 248 404 464
Arrangements divested (10) 13  
Currency exchange rate (loss)/gain 91 (135)  
Ending balance (1,551) (2,499) $ (2,542)
Pension benefits [member]      
Disclosure of net defined benefit liability (asset) [Line Items]      
Beginning balance (1,501)    
Amounts recognised in Income statement (242)    
Amounts recognised in Other comprehensive income 812    
Contributions by employer 204    
Arrangements divested (10)    
Currency exchange rate (loss)/gain 57    
Ending balance (680) (1,501)  
Other Benefits [member]      
Disclosure of net defined benefit liability (asset) [Line Items]      
Beginning balance (998)    
Amounts recognised in Income statement (46)    
Amounts recognised in Other comprehensive income 95    
Contributions by employer 44    
Currency exchange rate (loss)/gain 34    
Ending balance $ (871) $ (998)