Insurance Liabilities - Liability for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 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	$ 70,393	$ 75,167
Reinsurance recoverable	(30,289)	(32,102)
Net Liability for unpaid loss and loss adjustment expenses, beginning of year	40,104	43,065
Losses and loss adjustment expenses incurred:
Current year	3,365	3,784
Prior years, excluding discount and amortization of deferred gain	0	(27)
Prior years, discount charge (benefit)	106	94
Prior years, amortization of deferred gain on retroactive reinsurance	(32)	(60)
Total losses and loss adjustment expenses incurred	3,439	3,791
Losses and loss adjustment expenses paid:
Current year	(286)	(289)
Prior years	(2,857)	(3,549)
Total losses and loss adjustment expenses paid	(3,143)	(3,838)
Other changes:
Foreign exchange effect	(496)	397
Retroactive reinsurance adjustment (net of discount)	(8)	12
Reclassified to held for sale, net of reinsurance recoverables	(5)	0
Total other changes	(509)	409
Net liability for unpaid losses and loss adjustment expenses	39,891	43,427
Reinsurance recoverable	30,169	32,366
Total	70,060	75,793
Change in discount on loss reserves ceded under retroactive reinsurance	55	70
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 5	$ 7