Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jan. 31, 2014
Earnings Per Share [Abstract]
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		1,557,275	12,644,654
Profit for the period (A) (in dollars)	[1]	$ 1,665	$ 192
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		598,000,000	587,500,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		10,000,000	5,700,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	608,000,000	593,200,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 2.78	$ 0.33
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 2.74	$ 0.32
Shares outstanding as of March 31 (in shares)		597,900,000	589,100,000
Common stock repurchase
Stock repurchase program, authorized amount				$ 10,000
Common shares repurchased (in shares)		3,147,629	0
Payments for repurchase of common stock		$ 500	$ 0
Stock repurchase program, amount of authorized repurchase spent to date		$ 5,000

[1] 1 Profit attributable to common shareholders.

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