Net income (loss) per common share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income (loss) per common share
Income (loss) from continuing operations	$ 14	$ 84	$ (25)	$ 6
Income from discontinued operations, net of tax		1		337
Net income (loss)	$ 14	$ 85	$ (25)	$ 343
Weighted average number of common shares outstanding - basic (in shares)	72.6	61.0	69.9	60.6
Weighted dilutive effect of equity awards (in shares)	2.1	2.4		1.9
Weighted average number of common shares outstanding - diluted (in shares)	74.7	63.4	69.9	62.5
Basic net income (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	$ 0.19	$ 1.38	$ (0.36)	$ 0.10
Income from discontinued operations, net of tax (in dollars per share)		0.02		5.56
Basic net income (loss) per common share (in dollars per share)	0.19	1.40	(0.36)	5.66
Diluted net income (loss) per common share:
Income (loss) from continuing operations (in dollars per share)	0.19	1.32	(0.36)	0.10
Income from discontinued operations, net of tax (in dollars per share)		0.02		5.39
Diluted net income (loss) per common share (in dollars per share)	$ 0.19	$ 1.34	$ (0.36)	$ 5.49