Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic EPS
Income (loss) from continuing operations	$ 190	$ (238)	$ 814	$ (734)
Discontinued operations, net		(3)		432
Net income (loss)	190	(241)	814	(302)
Less: Net income allocated to participating securities	(1)		(4)
Net income (loss), net of participating securities	$ 189	$ (241)	$ 810	$ (302)
Weighted average number of basic shares	765.5	764.0	764.9	763.7
Basic EPS (in dollars per share)	$ 0.25	$ (0.32)	$ 1.06	$ (0.40)
Diluted EPS
Net income (loss), net of participating securities	$ 189	$ (241)	$ 810	$ (302)
Weighted average number of basic shares	765.5	764.0	764.9	763.7
Dilutive effect of potentially dilutive securities (in shares)	0.9		0.8
Total diluted weighted average common shares	766.4	764.0	765.7	763.7
Diluted EPS (in dollars per share)	$ 0.25	$ (0.32)	$ 1.06	$ (0.40)