Equity - Share-based payments (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 expense
Pre-tax compensation expense	$ 4	$ 4	$ 14	$ 15
Income tax benefit		(2)	(1)	(4)
Total share-based compensation expense, net of income taxes	4	2	13	11
Stock options
Share-based compensation expense
Pre-tax compensation expense		1	2	4
Income tax benefit				(1)
Total share-based compensation expense, net of income taxes		1	2	3
Restricted stock units (RSUs)
Share-based compensation expense
Pre-tax compensation expense	2	3	7	9
Income tax benefit		(1)	(1)	(2)
Total share-based compensation expense, net of income taxes	2	2	6	7
Performance shares and other share-based awards
Share-based compensation expense
Pre-tax compensation expense	2		5	2
Income tax benefit		(1)		(1)
Total share-based compensation expense, net of income taxes	$ 2	$ (1)	$ 5	$ 1