Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jan. 31, 2014
Earnings Per Share [Abstract]
Profit for the period (A) (in dollars)	[1]	$ 283	$ 559	$ 1,104	$ 2,606
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		584,700,000	588,400,000	583,800,000	597,900,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		4,900,000	6,400,000	4,900,000	7,400,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	589,600,000	594,800,000	588,700,000	605,300,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 0.48	$ 0.95	$ 1.89	$ 4.36
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 0.48	$ 0.94	$ 1.88	$ 4.30
Shares outstanding as of September 30 (in shares)		585,100,000	582,200,000	585,100,000	582,200,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		21,874,118	22,281,448	26,088,324	22,281,448
Common stock repurchase
Stock repurchase program, authorized amount						$ 10,000
Common shares repurchased (in shares)			19,600,000	0	25,841,608
Payments for repurchase of common stock			$ 1,500	$ 0	$ 2,025
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.