Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Jan. 31, 2014	Feb. 28, 2007
Earnings Per Share [Abstract]
Profit for the period (A) (in dollars)	[1]	$ 368	$ 1,017		$ 2,189	$ 2,938
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		588,400,000	611,500,000		597,900,000	620,600,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		6,400,000	11,300,000		7,400,000	12,100,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	594,800,000	622,800,000		605,300,000	632,700,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 0.63	$ 1.66		$ 3.66	$ 4.73
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 0.62	$ 1.63		$ 3.62	$ 4.64
Shares outstanding as of September 30 (in shares)		582,200,000	605,400,000		582,200,000	605,400,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		22,281,448	7,494,204		22,281,448	10,288,573
Common stock repurchase
Stock repurchase program, authorized amount							$ 10,000	$ 7,500
Common shares repurchased (in shares)		19,600,000.0	23,700,000.0	18,110,735	25,841,608	41,762,325
Payments for repurchase of common stock		$ 1,500	$ 2,500	$ 1,700	$ 2,025	$ 4,238
Stock repurchase program, amount of authorized repurchase spent to date					$ 4,500

[1] 1 Profit attributable to common stockholders.

[2] 2 Diluted by assumed exercise of stock-based compensation awards using the treasury stock method.