Insurance Liabilities - Liability for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Reconciliation of activity in the Liability for unpaid claims and claims adjustment expense:
Liability for unpaid loss and loss adjustment expenses, beginning of year	$ 69,168	$ 70,393	$ 75,167
Reinsurance recoverable	(29,026)	(30,289)	(32,102)
Net Liability for unpaid loss and loss adjustment expenses, beginning of year	40,142	40,104	43,065
Losses and loss adjustment expenses incurred:
Current year	14,440	14,363	15,100
Prior years, excluding discount and amortization of deferred gain	(216)	254	(392)
Prior years, discount charge (benefit)	168	354	307
Prior years, amortization of deferred gain on retroactive reinsurance	(230)	(404)	(81)
Total losses and loss adjustment expenses incurred	14,162	14,567	14,934
Losses and loss adjustment expenses paid:
Current year	(3,901)	(3,694)	(3,836)
Prior years	(9,975)	(9,849)	(11,868)
Total losses and loss adjustment expenses paid	(13,876)	(13,543)	(15,704)
Other changes:
Foreign exchange effect	1,233	(996)	606
Losses and loss adjustment expenses recognized within gain on divestitures	58	0	569
Retroactive reinsurance adjustment (net of discount)	76	15	158
Dispositions	0	(5)	(3,505)
Reclassified to held for sale, net of reinsurance recoverables	0	0	(19)
Total other changes	1,367	(986)	(2,191)
Net liability for unpaid losses and loss adjustment expenses	41,795	40,142	40,104
Reinsurance recoverable	28,871	29,026	30,289
Total	70,666	69,168	70,393
Change in discount on loss reserves ceded under retroactive reinsurance	45	168	150
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 72	$ 82	$ 33