Goodwill and other intangible assets - Intangible assets - Narrative (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Intangible asset amortization expense	$ 1,300	$ 905
Intangible assets with indefinite lives, excluding goodwill	20,500		$ 18,300
Railroad, Utilities and Energy [Member] | PTC [Member] | Other Assets [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Net carrying value	$ 6,400