Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic EPS Calculation
Earnings available to common stockholders - Basic	$ (497)	$ 4,587	$ 19,241
Weighted-average number of common shares outstanding (in shares)	1,872	1,867	1,883
Add: Deferred awards held as stock units (in shares)	1	1	1
Total weighted-average number of common shares outstanding (in shares)	1,873	1,868	1,884
Earnings per share of common stock - Basic (in dollars per share)	$ (0.27)	$ 2.46	$ 10.21
Diluted EPS Calculation
Earnings available to common stockholders - Diluted	$ (497)	$ 4,587	$ 19,241
Weighted-average number of common shares outstanding (in shares)	1,872	1,867	1,883
Add: Deferred awards held as stock units (in shares)	1	1	1
Add: Dilutive effect of employee stock-based awards (in shares)	0	7	14
Total weighted-average number of common shares outstanding (in shares)	1,873	1,875	1,898
Earnings per share of common stock - Diluted (in dollars per share)	$ (0.27)	$ 2.45	$ 10.14
Employee-based Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of EPS	10