Income taxes - Reconciliation of the U.S. federal statutory rate to effective rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Taxes at U.S. statutory rate	$ 2,809	$ 2,740	$ 1,838
Taxes at U. S. statutory rate (as a percent)	21.00%	21.00%	21.00%
(Decreases) increases resulting from:
Non-U.S. subsidiaries taxed at other than the U.S. rate	$ 186	$ 129	$ 184
State and local taxes, net of federal	121	93	91
U.S. tax incentives	(245)	(170)	(166)
Tax law change related to currency translation	(224)	0	0
Nondeductible goodwill	0	0	159
Other—net	(18)	(11)	(39)
Total provision (benefit) for income taxes	$ 2,629	$ 2,781	$ 2,067
Non-U.S. subsidiaries taxed at other than the U.S, rate (as a percentage)	1.40%	1.00%	2.10%
State and local taxes, net of federal (as a percent)	0.90%	0.70%	1.00%
U.S. tax incentives (as a percent)	(1.80%)	(1.30%)	(1.90%)
Tax law change related to currency translation (as a percent)	(0.017)	0	0
Nondeductible goodwill (as a percent)	0.00%	0.00%	1.80%
Other-net (as a percent)	(0.10%)	(0.10%)	(0.40%)
Provision (benefit) for income taxes (as a percent)	19.70%	21.30%	23.60%