Income taxes - Deferred income tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets:
Noncurrent deferred and refundable income taxes	$ 3,191	$ 2,634
Liabilities:
Other liabilities	432	454
Deferred income taxes—net	2,759	2,180
Deferred income tax assets:
Research expenditures	1,735	1,350
Tax carryforwards	1,346	1,389
Postemployment benefits	560	656
Employee compensation and benefits	531	634
Warranty reserves	303	325
Post sale discounts	260	253
Inventory valuation	183	138
Lease obligations	151	144
Other—net	288	205
Deferred income tax assets, total	5,357	5,094
Deferred income tax liabilities:
Capital and intangible assets, including lease basis differences	(1,270)	(1,312)
Other outside basis differences	(253)	(267)
Undistributed profits, including translation adjustments	(201)	(401)
Deferred income tax liabilities, total	(1,724)	(1,980)
Valuation allowance for deferred tax assets	(874)	(934)
Deferred income taxes—net	$ 2,759	$ 2,180