Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Jul. 01, 2018
Earnings Per Share [Abstract]
Profit for the period (A) (in dollars)		$ 1,092	$ 1,881
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		546,800,000	572,400,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		4,300,000	6,400,000
Average common shares outstanding for fully diluted computation (C) (in shares)		551,100,000	578,800,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 2.00	$ 3.29
Assuming full dilution (A/C) (in dollars per share)		$ 1.98	$ 3.25
Shares outstanding as of March 31 (in millions)		542,000,000.0	571,700,000
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		4,900,000	3,000,000.0
Stock repurchase
Stock repurchase program, authorized amount				$ 10,000
Stock repurchase program, remaining authorized repurchase amount		$ 4,900
Common shares repurchased (in shares)		9,328,184	5,699,525
Cost of repurchase	[1]	$ 1,163	$ 751

[1] See Note 12 for additional information.