v3.19.1
Earnings per share - Schedule of Numbers of Shares Earnings Per Share (Detail) - shares
shares in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Weighted average number of shares in issue      
Basic 4,914 4,886 4,860
Dilution for share options and awards 57 55 49
Diluted 4,971 4,941 4,909