Share-Based Compensation Plans - Share-based compensation expenses recognized (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 72	$ 67	$ 252	$ 214
Restricted share units (“RSUs”)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	42	41	155	145
Performance share awards (“PSAs”)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	28	24	90	63
Employee share purchase plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 2	$ 2	$ 7	$ 6