Equity method investments - Unaudited financial information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule Of Equity Method Investments [Line Items]
Assets	$ 1,019,933			$ 1,019,933			$ 948,465
Liabilities	485,206			485,206			466,784
Sales/ Total revenues and other income	93,210		$ 76,904	271,106		$ 223,948
The Kraft Heinz Company [Member]
Schedule Of Equity Method Investments [Line Items]
Assets	89,656			89,656			90,513
Liabilities	40,198			40,198			41,643
Sales/ Total revenues and other income	6,570		6,505	19,780		19,104
Net earnings attributable to common shareholders	$ 262		$ 432	$ 2,098		$ 1,473
Occidental Petroleum Corporation [Member]
Schedule Of Equity Method Investments [Line Items]
Assets		$ 71,199			$ 71,199		72,609
Liabilities		42,088			42,088		$ 42,524
Sales/ Total revenues and other income		6,731			22,315
Net earnings attributable to common shareholders		$ 605			$ 3,315