Share-Based Compensation Plans - Share-based compensation expenses recognized (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 91	$ 70	$ 180	$ 147
Restricted share units (“RSUs”)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	50	46	113	104
Performance share awards (“PSAs”)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	39	23	62	39
Employee share purchase plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 2	$ 1	$ 5	$ 4