Selected quarterly financial results (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2017	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Sales and revenues	$ 11,235	$ 9,881	$ 9,997	$ 10,635	$ 13,144	$ 12,758	$ 14,432	$ 13,466		$ 41,748		$ 53,800		$ 54,722
Cost of goods sold	7,784	6,919	7,113	7,266	9,117	8,569	9,941	9,003		29,082		36,630		36,997
Gross margin	2,786	2,309	2,197	2,648	3,269	3,405	3,730	3,721
Profit (loss)	$ 780	$ 668	$ 458	$ 1,092	$ 1,098	$ 1,494	$ 1,620	$ 1,881		$ 2,998	[1]	$ 6,093	[1]	$ 6,147	[1]
Profit (loss) per common share (in dollars per share)	$ 1.43	$ 1.23	$ 0.84	$ 2.00	$ 2.00	$ 2.69	$ 2.85	$ 3.29		$ 5.51		$ 10.85		$ 10.39
Profit (loss) per common share - diluted (in dollars per share)	$ 1.42	$ 1.22	$ 0.84	$ 1.98	$ 1.97	$ 2.66	$ 2.83	$ 3.25		$ 5.46	[2]	$ 10.74	[2]	$ 10.26	[2]
Pre-tax pension and other postretirement benefit plan actuarial losses	$ (438)	$ (77)	$ (122)	$ 254	$ (468)					$ (383)		$ (468)		$ (495)
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount														(25)
Charge/ (benefit) to U.S. deferred tax rate change 2017 U.S. tax reform														$ 154
Taxes at U. S. statutory rate (as a percent)										21.00%		21.00%		21.00%		35.00%
Correction of Prior Year Valuation Allowance														$ 59
Valuation allowances										$ 0		$ 0		(29)
Adjustment to estimated tax for mandatory deemed repatriation of non-U.S. earnings								$ 178				178		50
U.S. 2017 tax reform estimated impact									$ 2,371
U.S. state taxing jurisdictions
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount														(63)
Financial Products
Sales and revenues	665	653	687	721	758	$ 784	$ 761	742		2,726		3,045		2,900
Machinery, Energy & Transportation
Sales and revenues	$ 10,570	$ 9,228	$ 9,310	$ 9,914	$ 12,386	$ 11,974	$ 13,671	$ 12,724		$ 39,022		$ 50,755		$ 51,822

[1] Profit attributable to common shareholders.

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