Property, plant and equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Property, plant and equipment
Total property, plant and equipment, at cost	$ 29,781		$ 31,538
Less: Accumulated depreciation	(16,207)		(17,383)
Property, plant and equipment - net	13,574	$ 13,965	14,155
Commitments for the purchase or construction of capital assets	124
Assets recorded under capital leases
Gross capital leases	129		96
Less: Accumulated depreciation	(27)		(19)
Net capital leases	102		77
Minimum rental payments on assets recorded under capital leases were:
2019	8
2020	9
2021	29
2022	9
2023	7
Thereafter	32
Minimum rental payments to be received for equipment leased to others were:
2019	896
2020	574
2021	314
2022	158
2023	71
Thereafter	69
Land
Property, plant and equipment
Total property, plant and equipment, at cost	671		664
Buildings and land improvements
Property, plant and equipment
Total property, plant and equipment, at cost	6,977		7,515
Machinery, equipment and other
Property, plant and equipment
Total property, plant and equipment, at cost	13,733		14,888
Software
Property, plant and equipment
Total property, plant and equipment, at cost	1,703		1,745
Equipment leased to others
Property, plant and equipment
Total property, plant and equipment, at cost	6,015		6,038
Less: Accumulated depreciation	(1,744)		(1,656)
Property, plant and equipment - net	4,271		4,382
Construction-in-process
Property, plant and equipment
Total property, plant and equipment, at cost	$ 682		$ 688
Minimum | Buildings and land improvements
Property, plant and equipment
Useful Lives (Years)	20 years
Minimum | Machinery, equipment and other
Property, plant and equipment
Useful Lives (Years)	2 years
Minimum | Software
Property, plant and equipment
Useful Lives (Years)	3 years
Minimum | Equipment leased to others
Property, plant and equipment
Useful Lives (Years)	1 year
Maximum | Buildings and land improvements
Property, plant and equipment
Useful Lives (Years)	45 years
Maximum | Machinery, equipment and other
Property, plant and equipment
Useful Lives (Years)	10 years
Maximum | Software
Property, plant and equipment
Useful Lives (Years)	7 years
Maximum | Equipment leased to others
Property, plant and equipment
Useful Lives (Years)	7 years