Insurance Liabilities - Liability for unpaid losses and loss adjustment expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reconciliation of activity in the Liability for unpaid claims and claims adjustment expense:
Liability for unpaid loss and loss adjustment expenses, beginning of period	$ 75,793	$ 78,183	$ 75,167	$ 79,026
Reinsurance recoverable	(32,366)	(34,321)	(32,102)	(35,213)
Net Liability for unpaid loss and loss adjustment expenses, beginning of period	43,427	43,862	43,065	43,813
Losses and loss adjustment expenses incurred:
Current year	3,945	3,765	7,729	7,647
Prior years, excluding discount and amortization of deferred gain	(107)	(374)	(134)	(425)
Prior years, discount charge (benefit)	54	38	148	42
Prior years, amortization of deferred gain on retroactive reinsurance	(25)	28	(85)	(14)
Total losses and loss adjustment expenses incurred	3,867	3,457	7,658	7,250
Losses and loss adjustment expenses paid:
Current year	(881)	(834)	(1,170)	(1,157)
Prior years	(2,994)	(2,729)	(6,543)	(6,171)
Total losses and loss adjustment expenses paid	(3,875)	(3,563)	(7,713)	(7,328)
Other changes:
Foreign exchange effect	(25)	(800)	372	(796)
Retroactive reinsurance adjustment (net of discount)	47	200	59	217
Reclassified to held for sale, net of reinsurance recoverables	(3,383)		(3,383)
Total other changes	(3,361)	(600)	(2,952)	(579)
Net liability for unpaid losses and loss adjustment expenses	40,058	43,156	40,058	43,156
Reinsurance recoverable(c)	30,226	33,583	30,226	33,583
Total	70,284	76,739	70,284	76,739
Change in discount on loss reserves ceded under retroactive reinsurance	26	18	96	57
Disposal Group, Including Discontinued Operation, Assets
Other changes:
Reinsurance recoverable(c)		1,500		1,500
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 6	$ 6	$ 13	$ 10