Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic EPS
Income (loss) from continuing operations	$ 507	$ (136)	$ 624	$ (496)
Discontinued operations, net		(3)		435
Net income (loss)	507	(139)	624	(61)
Less: Net income allocated to participating securities	(2)		(2)
Net income (loss), net of participating securities	$ 505	$ (139)	$ 622	$ (61)
Weighted average number of basic shares	764.9	763.6	764.7	763.5
Basic EPS (in dollars per share)	$ 0.66	$ (0.18)	$ 0.81	$ (0.08)
Diluted EPS
Net income (loss), net of participating securities	$ 505	$ (139)	$ 622	$ (61)
Weighted average number of basic shares	764.9	763.6	764.7	763.5
Dilutive effect of potentially dilutive securities (in shares)	1.0		0.8
Total diluted weighted average common shares	765.9	763.6	765.5	763.5
Diluted EPS (in dollars per share)	$ 0.66	$ (0.18)	$ 0.81	$ (0.08)