Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic EPS
Net income (loss)	$ 848	$ 507	$ 1,556	$ 624
Less: Net income allocated to participating securities	(5)	(2)	(8)	(2)
Net income, net of participating securities	$ 843	$ 505	$ 1,548	$ 622
Weighted average number of basic shares	765.7	764.9	765.7	764.7
Basic EPS (in dollars per share)	$ 1.10	$ 0.66	$ 2.02	$ 0.81
Diluted EPS
Net income, net of participating securities	$ 843	$ 505	$ 1,548	$ 622
Weighted average number of basic shares	765.7	764.9	765.7	764.7
Dilutive effect of potentially dilutive securities (in shares)	1.7	1.0	1.5	0.8
Total diluted weighted average common shares	767.4	765.9	767.2	765.5
Diluted EPS (in dollars per share)	$ 1.10	$ 0.66	$ 2.02	$ 0.81