Other receivables - Narrative (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Aggregate provisions for credit losses on receivables	$ 399	$ 328
Charge-offs, net of recoveries	384	$ 284
Railroad, Utilities and Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	5,795		$ 4,182
Railroad, Utilities and Energy [Member] | PTC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 2,000