Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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)		2,962,190	1,471,071
Profit for the period (A) (in dollars)	[1]	$ 1,494	$ 1,727	$ 4,995	$ 5,099
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)		556,300,000	592,100,000	565,200,000	595,300,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)		4,900,000	7,300,000	5,600,000	8,500,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]	561,200,000	599,400,000	570,800,000	603,800,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)		$ 2.69	$ 2.92	$ 8.84	$ 8.57
Assuming full dilution (A/C) (in dollars per share)	[2]	$ 2.66	$ 2.88	$ 8.75	$ 8.45
Shares outstanding as of September 30 (in millions)		552,700,000	590,100,000	552,700,000	590,100,000
Common stock repurchase
Stock repurchase program, authorized amount						$ 10,000
Stock repurchase program, remaining authorized repurchase amount		$ 6,700		$ 6,700
Common shares repurchased (in shares)		10,300,000	4,800,000	25,792,061	12,804,035
Payments for repurchase of common stock		$ 1,300	$ 750	$ 3,283	$ 2,000

[1] Profit attributable to common shareholders.

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