Insurance Liabilities - Liability for unpaid losses and loss adjustment expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of activity in the Liability for unpaid claims and claims adjustment expense:
Liability for unpaid loss and loss adjustment expenses, beginning of year	$ 75,167	$ 79,026	$ 77,720
Reinsurance recoverable	(32,102)	(35,213)	(34,431)
Net Liability for unpaid loss and loss adjustment expenses, beginning of year	43,065	43,813	43,289
Losses and loss adjustment expenses incurred:
Current year	15,100	16,434	16,434
Prior years, excluding discount and amortization of deferred gain	(392)	(530)	(171)
Prior years, discount charge (benefit)	307	(605)	(131)
Prior years, amortization of deferred gain on retroactive reinsurance	(81)	(252)	(190)
Total losses and loss adjustment expenses incurred	14,934	15,047	15,942
Losses and loss adjustment expenses paid:
Current year	(3,836)	(4,011)	(3,868)
Prior years	(11,868)	(11,066)	(11,503)
Total losses and loss adjustment expenses paid	(15,704)	(15,077)	(15,371)
Other changes:
Foreign exchange effect	606	(1,463)	(593)
Losses and loss adjustment expenses recognized within gain on divestitures	569	0	0
Retroactive reinsurance adjustment (net of discount)	158	745	546
Dispositions(c)	(3,505)	0	0
Reclassified to held for sale, net of reinsurance recoverables	(19)	0	0
Total other changes	(2,191)	(718)	(47)
Net liability for unpaid losses and loss adjustment expenses	40,104	43,065	43,813
Reinsurance recoverable	30,289	32,102	35,213
Total	70,393	75,167	79,026
Change in discount on loss reserves ceded under retroactive reinsurance	150	(301)	(42)
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 33	$ 63	$ 53