Intangible assets and goodwill (Details Intangible assets) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 02, 2018
Intangible assets by major class
Weighted Amortizable Life (in years)	14 years	14 years
Gross Carrying Amount	$ 4,151	$ 4,219
Accumulated Amortization	(2,586)	(2,322)
Net	1,565	1,897
Amortization expense	324	$ 331	$ 323
Intangible Assets, Expected Amortization Expense
2020	310
2021	292
2022	273
2023	215
2024	158
Thereafter	$ 317
ECM S.p.A.
Intangible assets by major class
Finite-lived intangible assets acquired				$ 112
Downer Freight Rail
Intangible assets by major class
Finite-lived intangible assets acquired				$ 6
Customer relationships
Intangible assets by major class
Weighted Amortizable Life (in years)	15 years	15 years
Gross Carrying Amount	$ 2,450	$ 2,463
Accumulated Amortization	(1,406)	(1,249)
Net	$ 1,044	$ 1,214
Intellectual property
Intangible assets by major class
Weighted Amortizable Life (in years)	12 years	11 years
Gross Carrying Amount	$ 1,510	$ 1,557
Accumulated Amortization	(1,055)	(965)
Net	$ 455	$ 592
Other
Intangible assets by major class
Weighted Amortizable Life (in years)	13 years	13 years
Gross Carrying Amount	$ 191	$ 199
Accumulated Amortization	(125)	(108)
Net	$ 66	$ 91