Operations and summary of significant accounting policies (Details 4- Pension) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold	$ 9,987	$ 9,022	$ 9,422	$ 8,566	$ 8,965	$ 7,678	$ 7,816	$ 6,801	$ 36,997	$ 31,260	$ 28,044
Selling, general and administrative expenses									5,478	4,999	4,383
Research and development expenses									1,850	1,842	1,853
Other operating (income) expenses									1,382	2,255	1,904
Total operating costs									46,429	41,002	37,375
Operating profit									8,293	4,460	1,162
Other income (expense)									$ (67)	153	(518)
Components of net periodic benefit cost
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold										211	(265)
Selling, general and administrative expenses										(178)	(303)
Research and development expenses										(63)	(98)
Other operating (income) expenses										(24)	2
Total operating costs										(54)	(664)
Operating profit										54	664
Other income (expense)										(54)	(664)
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold										31,049	28,309
Selling, general and administrative expenses										5,177	4,686
Research and development expenses										1,905	1,951
Other operating (income) expenses										2,279	1,902
Total operating costs										41,056	38,039
Operating profit										4,406	498
Other income (expense)										$ 207	$ 146