Selected quarterly financial results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	May 01, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Sales and revenues		$ 12,896	$ 11,413	$ 11,331	$ 9,822	$ 9,574	$ 9,160	$ 10,342	$ 9,461	$ 45,462		$ 38,537		$ 47,011
Less: Revenues		(702)	(700)	(692)	(692)	(689)	(697)	(697)	(681)	(2,786)		(2,764)		(2,864)
Sales		12,194	10,713	10,639	9,130	8,885	8,463	9,645	8,780	42,676		35,773		44,147
Cost of goods sold		8,889	7,633	7,769	6,758	7,541	6,527	7,419	6,822	31,049		28,309		33,546
Gross margin		3,305	3,080	2,870	2,372	1,344	1,936	2,226	1,958
Profit (loss)		$ (1,299)	$ 1,059	$ 802	$ 192	$ (1,171)	$ 283	$ 550	$ 271	$ 754	[1]	$ (67)	[1]	$ 2,512	[1]
Profit (loss) per common share		$ (2.18)	$ 1.79	$ 1.36	$ 0.33	$ (2.00)	$ 0.48	$ 0.94	$ 0.46	$ 1.27		$ (0.11)		$ 4.23
Profit (loss) per common share - diluted		$ (2.18)	$ 1.77	$ 1.35	$ 0.32	$ (2.00)	$ 0.48	$ 0.93	$ 0.46	$ 1.26	[2],[3]	$ (0.11)	[2],[3]	$ 4.18	[2],[3]
Restructuring costs										$ 1,256		$ 1,019		$ 898
Pre-tax pension and other postretirement benefit plan actuarial losses		$ (301)				$ (985)				(301)		(985)		(179)
Goodwill impairment charge		595								0		595		$ 0
Deferred Tax Assets, Valuation Allowance, Current		$ 111				$ 141				111		$ 141
U.S. 2017 tax reform estimated impact										$ 2,371
Iron Planet Holdings, Inc. investment [Domain]
Equity Method Investment, Realized Gain (Loss) on Disposal	$ 85

[1] 1 Profit (loss) attributable to common shareholders.

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

[3] 3 In 2016, the assumed exercise of stock-based compensation awards was not considered because the impact would be antidilutive.