Profit per share (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020	Dec. 31, 2019	Jul. 01, 2018
Earnings Per Share [Abstract]
Profit for the period (A) (in millions of dollars)	[1]	$ 6,489		$ 2,998	$ 6,093
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		544,000,000.0		544,100,000	561,600,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		4,500,000		4,500,000	5,900,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	548,500,000		548,600,000	567,500,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 11.93		$ 5.51	$ 10.85
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 11.83		$ 5.46	$ 10.74
Shares outstanding as of December 31		535,900,000		545,300,000	550,100,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		1,100,000		4,600,000	3,000,000
Common Stock Repurchase
Stock Repurchase Program, Authorized Amount						$ 10,000
Common shares repurchased (in shares)		12,987,299		10,096,006	30,586,507
Payments for repurchase of common stock		$ 2,668		$ 1,130	$ 4,047
Stock Repurchase Program, Remaining Authorized Repurchase Amount		2,100
Common shares repurchased		$ 2,668	[3]	$ 1,250	$ 3,928

[1] Profit attributable to common shareholders.

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

[3] See Note 16 regarding shares repurchased.