Income taxes - Provision for income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. federal - Current	$ 943	$ 1,235	$ 948
Non-U.S. - Current	240	212	169
U.S. state - Current	24	27	18
Total current income tax expense (benefit)	1,207	1,474	1,135
U.S. federal - Deferred	(277)	(223)	(23)
Non-U.S. - Deferred	(22)	32	38
U.S. state - Deferred	0	0	0
Total deferred income tax expense (benefit)	(299)	(191)	15
Total U.S. federal income taxes	666	1,012	925
Total Non-U.S. income taxes	218	244	207
Total U.S. state income taxes	24	27	18
Provision for income taxes	$ 908	$ 1,283	$ 1,150