Postemployment benefit plans - Company costs related to U.S. and non-U.S. defined contribution plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure
Costs related to defined contribution plans	$ 681	$ 506	$ 554
U.S. plans
Defined Benefit Plan Disclosure
Costs related to defined contribution plans	567	392	440
Non-U.S. plans
Defined Benefit Plan Disclosure
Costs related to defined contribution plans	$ 114	$ 114	$ 114