Profit Per Share (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended			6 Months Ended
		May 31, 2018	Jun. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jul. 01, 2018	Jan. 31, 2014
Earnings Per Share [Abstract]
Common shares under SARs and stock options not included in the computation of diluted earnings per share (in shares)				1,478,726		8,062,177
Accelerated share repurchase, amount		$ 500
Profit for the period (A) (in dollars)	[1]			$ 1,707		$ 802	$ 3,372	$ 994
Determination of shares (in millions)
Weighted-average number of common shares outstanding (B) (in shares)				596,200,000		590,200,000	597,000,000	588,800,000
Shares issuable on exercise of stock awards, net of shares assumed to be purchased out of proceeds at average market price (in shares)				8,000,000		5,200,000	9,100,000	5,600,000
Average common shares outstanding for fully diluted computation (C) (in shares)	[2]			604,200,000		595,400,000	606,100,000	594,400,000
Profit (loss) per share of common stock:
Assuming no dilution (A/B) (in dollars per share)				$ 2.86		$ 1.36	$ 5.65	$ 1.69
Assuming full dilution (A/C) (in dollars per share)	[2]			$ 2.82		$ 1.35	$ 5.56	$ 1.67
Shares outstanding as of June 30 (in shares)			594,300,000	594,300,000		591,000,000	594,300,000	591,000,000
Common stock repurchase
Stock repurchase program, authorized amount									$ 10,000	$ 10,000
Common shares repurchased (in shares)		1,600,000	3,300,000		3,100,000		8,029,422	0
Payments for repurchase of common stock		$ 250		$ 750	$ 500		$ 1,250	$ 0
Stock repurchase program, remaining authorized repurchase amount			$ 4,200	$ 4,200			$ 4,200

[1] 1 Profit attributable to common shareholders.

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