Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic EPS Calculation
Earnings available to common stockholders - Basic	[1]	$ 4,587	$ 19,241	$ 21,423
Weighted-average number of common shares outstanding		1,867	1,883	1,916
Add: Deferred awards held as stock units		1	1	1
Total weighted-average number of common shares outstanding		1,868	1,884	1,917
Earnings per share of common stock - Basic		$ 2.46	$ 10.21	$ 11.18
Diluted EPS Calculation
Earnings available to common stockholders - Diluted	[1]	$ 4,587	$ 19,241	$ 21,423
Weighted-average number of common shares outstanding		1,867	1,883	1,916
Add: Deferred awards held as stock units		1	1	1
Add: Dilutive effect of employee stock-based awards		7	14	15
Total weighted-average number of common shares outstanding		1,875	1,898	1,932
Earnings per share of common stock - Diluted		$ 2.45	$ 10.14	$ 11.09

[1] There was no effect of dividend equivalents paid on stock units or dilutive impact of employee stock-based awards on earnings.