Other receivables - Narrative (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Aggregate provisions for credit losses on receivables	$ 358	$ 399
Charge-offs, net of recoveries	364	$ 384
Railroad, Utilities and Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	6,588		$ 7,086
Railroad, Utilities and Energy [Member] | Pilot [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	$ 1,600		$ 2,100