XML 139 R106.htm IDEA: XBRL DOCUMENT v3.10.0.1
Equity (Share-based Payments to Employees, Non-marketable Options, Movement) (Details) - Non-marketable options [Member]
Pure in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Disclosure of terms and conditions of share-based payment arrangement [Line Items]    
Balance as at Start of Period 20 14
Granted during the year 6 7
Expired during the period (6)  
Forfeited during the year (1) (1)
Exercised during the year (1)  
Balance as at End of Period 18 20