Equity - Share-based payments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based compensation expense
Pre-tax compensation expense	$ 6	$ 6	$ 12	$ 10
Income tax benefit		(1)	(1)	(1)
Total share-based compensation expense, net of income taxes	6	5	11	9
Stock options
Share-based compensation expense
Pre-tax compensation expense	1	1	2	2
Total share-based compensation expense, net of income taxes	1	1	2	2
Restricted stock units (RSUs)
Share-based compensation expense
Pre-tax compensation expense	3	3	6	5
Income tax benefit		(1)	(1)	(1)
Total share-based compensation expense, net of income taxes	3	2	5	4
Performance shares and other share-based awards
Share-based compensation expense
Pre-tax compensation expense	2	2	4	3
Total share-based compensation expense, net of income taxes	$ 2	$ 2	$ 4	$ 3