Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Jul. 01, 2018
Accelerated Stock Repurchase Agreement [Line Items]
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)		2,986,014	1,557,275
Profit for the period (A) (in dollars)	[1]	$ 1,881	$ 1,665
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		572,400,000	598,000,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		6,400,000	10,000,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	578,800,000	608,000,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 3.29	$ 2.78
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 3.25	$ 2.74
Shares outstanding as of March 31 (in shares)		571,700,000	597,900,000
Common stock repurchase
Stock repurchase program, authorized amount				$ 10,000
Stock repurchase program, remaining authorized repurchase amount		$ 9,200
Common shares repurchased (in shares)		5,699,525	3,147,629
Payments for repurchase of common stock		$ 751	$ 500

[1] Profit attributable to common shareholders.

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