Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jan. 31, 2014
Earnings Per Share [Abstract]
Profit for the period (A) (in dollars)	[1]	$ 550	$ 802	$ 821	$ 2,047
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		584,100,000	603,200,000	583,400,000	604,100,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		4,500,000	7,500,000	4,800,000	7,700,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	588,600,000	610,700,000	588,200,000	611,800,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 0.94	$ 1.33	$ 1.41	$ 3.39
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 0.93	$ 1.31	$ 1.40	$ 3.34
Shares outstanding as of June 30 (in shares)		584,200,000	602,600,000	584,200,000	602,600,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		26,168,384	22,329,106	28,919,076	22,329,106
Common stock repurchase
Stock repurchase program, authorized amount						$ 10,000
Common shares repurchased (in shares)			1,400,000	0	6,208,074
Payments for repurchase of common stock			$ 125	$ 0	$ 525
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.