Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic EPS
Net income (loss)	$ 1,869	$ 190	$ 3,425	$ 814
Less: Net income allocated to participating securities	(8)	(1)	(16)	(4)
Net Income, net of participating securities	$ 1,861	$ 189	$ 3,409	$ 810
Weighted average number of basic shares (in shares)	761.7	765.5	764.3	764.9
Basic EPS (in dollars per share)	$ 2.44	$ 0.25	$ 4.46	$ 1.06
Diluted EPS
Net income, net of participating securities	$ 1,861	$ 189	$ 3,409	$ 810
Weighted average number of basic shares (in shares)	761.7	765.5	764.3	764.9
Dilutive effect of potentially dilutive securities (in shares)	1.6	0.9	1.5	0.8
Total diluted weighted average common shares (in shares)	763.3	766.4	765.8	765.7
Diluted EPS (in dollars per share)	$ 2.44	$ 0.25	$ 4.45	$ 1.06