Earnings per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings per share
Income from continuing operations		$ 139	$ (78)	$ 71
Income from discontinued operations, net of tax	$ 306	9	336	20
Net income	$ 306	$ 148	$ 258	$ 91
Weighted average number of common shares outstanding - basic (in shares)	60.6	59.6	60.4	59.6
Weighted dilutive effect of equity awards (in shares)	1.4	0.4		0.2
Weighted average number of common shares outstanding-diluted	62.0	60.0	60.4	59.8
Basic net income per common share:
Income from continuing operations (in dollars per share)		$ 2.33	$ (1.29)	$ 1.19
Income from discontinued operations, net of tax (in dollars per share)	$ 5.05	0.15	5.56	0.34
Basic income per common share (in dollars per share)	5.05	2.48	4.27	1.53
Diluted net income per common share:
Loss from continuing operations (in dollars per share)		2.32	(1.29)	1.19
Income from discontinued operations, net of tax (in dollars per share)	4.94	0.15	5.56	0.33
Diluted income per common share (in dollars per share)	$ 4.94	$ 2.47	$ 4.27	$ 1.52