Operations and summary of significant accounting policies (Details 3) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Income Statement [Abstract]
Cost of goods sold	$ 7,541	$ 6,527	$ 7,419	$ 6,822	$ 8,240	$ 7,872	$ 8,674	$ 8,760	$ 28,309		$ 33,546		$ 40,718
Selling, general and administrative expenses									4,686		4,951		6,529
Research and development expenses									1,951		2,119		2,380
Other operating (income) expenses									1,902		2,023		1,619
Total operating costs									38,039		43,226		51,870
Operating profit									498		3,785		3,314
Other income (expense)									146		161		322
Consolidated profit before taxes									139		3,439		3,152
Provision (benefit) for income taxes									192		916		692
Profit (loss) of consolidated companies									(53)		2,523		2,460
Profit (loss) of consolidated and affiliated companies									(59)		2,523		2,468
Profit (loss)	$ (1,171)	$ 283	$ 550	$ 271	$ (94)	$ 559	$ 802	$ 1,245	$ (67)	[1]	$ 2,512	[1]	$ 2,452	[1]
Profit (loss) per common share (in dollars per share)	$ (2.00)	$ 0.48	$ 0.94	$ 0.46	$ (0.16)	$ 0.95	$ 1.33	$ 2.06	$ (0.11)		$ 4.23		$ 3.97
Profit (loss) per common share - diluted (in dollars per share)	$ (2.00)	$ 0.48	$ 0.93	$ 0.46	$ (0.16)	$ 0.94	$ 1.31	$ 2.03	$ (0.11)	[2]	$ 4.18	[2]	$ 3.90	[2]
Statement of Comprehensive Income [Abstract]
Profit (loss) of consolidated and affiliated companies									$ (59)		$ 2,523		$ 2,468
Foreign currency translation, net of tax									(17)		(973)		(1,155)
Current year actuarial gain (loss),net of tax									0		0		0
Amortization of actuarial (gain) loss, net of tax									0		0		0
Other comprehensive income (loss), net of tax									(4)		(988)		(1,290)
Statement of Financial Position [Abstract]
Profit employed in the business	$ 27,377				$ 29,246				27,377		29,246
Accumulated other comprehensive income (loss)	(2,039)				(2,035)				(2,039)		(2,035)		(1,059)		$ 231
Statement of Stockholders' Equity [Abstract]
Profit (loss) of consolidated and affiliated companies									(59)		2,523		2,468
Foreign currency translation, net of tax									(17)		(973)		(1,155)
Pension and other postretirement benefits, net of tax									(83)		38		21
Statement of Cash Flows [Abstract]
Profit (loss) of consolidated and affiliated companies									(59)		2,523		2,468
Provision (benefit) for deferred income taxes									(431)		(307)		(954)
Adjustments for non-cash items: Actuarial (gain) loss on pension and postretirement benefits	985				214				985		179		2,624
Adjustment for non-cash items: Other									856		453		470
Other assets - net									224		143		(139)
Other liabilities - net									(388)		(146)		(359)
Previously Reported
Income Statement [Abstract]
Cost of goods sold									28,074		33,742		39,767
Selling, general and administrative expenses									4,441		5,199		5,697
Research and development expenses									1,868		2,165		2,135
Other operating (income) expenses											2,062		1,633
Total operating costs									37,476		43,755		49,856
Operating profit									1,061		3,256		5,328
Other income (expense)									50		106		239
Consolidated profit before taxes									606		2,855		5,083
Provision (benefit) for income taxes									364		742		1,380
Profit (loss) of consolidated companies									242		2,113		3,703
Profit (loss) of consolidated and affiliated companies									236		2,113		3,711
Profit (loss)									$ 228		$ 2,102		$ 3,695
Profit (loss) per common share (in dollars per share)									$ 0.39		$ 3.54		$ 5.99
Profit (loss) per common share - diluted (in dollars per share)									$ 0.39		$ 3.50		$ 5.88
Statement of Comprehensive Income [Abstract]
Profit (loss) of consolidated and affiliated companies									$ 236		$ 2,113		$ 3,711
Foreign currency translation, net of tax									0		(977)		(1,164)
Current year actuarial gain (loss),net of tax									(621)		(10)		(1,578)
Amortization of actuarial (gain) loss, net of tax									(326)		(424)		(344)
Other comprehensive income (loss), net of tax									(299)		(578)		(2,533)
Statement of Financial Position [Abstract]
Profit employed in the business	32,634				34,208				32,634		34,208
Accumulated other comprehensive income (loss)	$ (7,296)				$ (6,997)				(7,296)		(6,997)
Statement of Stockholders' Equity [Abstract]
Profit (loss) of consolidated and affiliated companies									236		2,113		3,711
Foreign currency translation, net of tax									0		(977)		(1,164)
Pension and other postretirement benefits, net of tax									212		(376)		1,255
Statement of Cash Flows [Abstract]
Profit (loss) of consolidated and affiliated companies									236		2,113		3,711
Provision (benefit) for deferred income taxes									0		0		0
Adjustments for non-cash items: Actuarial (gain) loss on pension and postretirement benefits									0		0		0
Adjustment for non-cash items: Other									952		508		553
Other assets - net									46		(220)		(300)
Other liabilities - net									(47)		$ 444		$ 146
Adjustments for Change in Accounting Principle [Domain]
Statement of Comprehensive Income [Abstract]
Foreign currency translation, net of tax									0
Statement of Stockholders' Equity [Abstract]
Foreign currency translation, net of tax									$ 0

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

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