Insurance Liabilities - Liability for unpaid losses and loss adjustment expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
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
Reinsurance recoverable	(32,102)	(35,213)
Net Liability for unpaid loss and loss adjustment expenses, beginning of year	43,065	43,813
Losses and loss adjustment expenses incurred:
Current year	3,784	3,882
Prior years, excluding discount and amortization of deferred gain	(27)	(51)
Prior years, discount charge (benefit)	94	4
Prior years, amortization of deferred gain on retroactive reinsurance	(60)	(42)
Total losses and loss adjustment expenses incurred	3,791	3,793
Losses and loss adjustment expenses paid:
Current year	(289)	(323)
Prior years	(3,549)	(3,442)
Total losses and loss adjustment expenses paid	(3,838)	(3,765)
Other changes:
Foreign exchange effect	397	4
Retroactive reinsurance adjustment (net of discount)	12	17
Total other changes	409	21
Net liability for unpaid losses and loss adjustment expenses	43,427	43,862
Reinsurance recoverable	32,366	34,321
Total	75,793	78,183
Change in discount on loss reserves ceded under retroactive reinsurance	70	39
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 7	$ 4