Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019		Jul. 01, 2018
Earnings Per Share [Abstract]
Profit for the period (A) (in dollars)	$ 668	[1]	$ 1,494	[1]	$ 2,218	[2]	$ 4,995	[2]
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)	542,300,000		556,300,000		543,900,000		565,200,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)	4,100,000		4,900,000		3,900,000		5,600,000
Average common shares outstanding for fully diluted computation (C) (in shares)	546,400,000	[3]	561,200,000	[3]	547,800,000	[4]	570,800,000	[4]
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)	$ 1.23		$ 2.69		$ 4.08		$ 8.84
Assuming full dilution (A/C) (in dollars per share)	$ 1.22	[3]	$ 2.66	[3]	$ 4.05	[4]	$ 8.75	[4]
Shares outstanding as of September 30 (in millions)	543,300,000		552,700,000		543,300,000		552,700,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)	4,800,000		4,800,000		3,000,000.0		3,000,000.0
Stock repurchase
Stock repurchase program, authorized amount									$ 10,000
Stock repurchase program, remaining authorized repurchase amount	$ 4,800				$ 4,800
Common shares repurchased (in shares)	0		10,335,410		10,096,006		25,792,061
Cost of repurchase			$ 1,246	[5]	$ 1,250	[6]	$ 3,283	[6]
Cost of repurchase			$ 1,300		$ 1,130		$ 3,283

[1] Profit attributable to common shareholders.

[2] Profit attributable to common shareholders.

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

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

[5] See Note 12 for additional information.

[6] See Note 12 for additional information.