Insurance Liabilities - Liability for unpaid losses and loss adjustment expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reconciliation of activity in the Liability for unpaid claims and claims adjustment expense:
Liability for unpaid loss and loss adjustment expenses, beginning of period	$ 78,183	$ 78,832	$ 79,026	$ 77,720
Reinsurance recoverable	(34,321)	(35,271)	(35,213)	(34,431)
Net Liability for unpaid loss and loss adjustment expenses, beginning of period	43,862	43,561	43,813	43,289
Losses and loss adjustment expenses incurred:
Current year	3,765	3,870	7,647	7,795
Prior years, excluding discount and amortization of deferred gain	(374)	(29)	(425)	(13)
Prior years, discount charge (benefit)	38	34	42	16
Prior years, amortization of deferred gain on retroactive reinsurance	28	(22)	(14)	(94)
Total losses and loss adjustment expenses incurred	3,457	3,853	7,250	7,704
Losses and loss adjustment expenses paid:
Current year	(834)	(895)	(1,157)	(1,223)
Prior years	(2,729)	(2,620)	(6,171)	(6,204)
Total losses and loss adjustment expenses paid	(3,563)	(3,515)	(7,328)	(7,427)
Other changes:
Foreign exchange effect	(800)	113	(796)	357
Retroactive reinsurance adjustment (net of discount)	200	103	217	192
Total other changes	(600)	216	(579)	549
Net liability for unpaid losses and loss adjustment expenses	43,156	44,115	43,156	44,115
Reinsurance recoverable	33,583	34,866	33,583	34,866
Total	76,739	78,981	76,739	78,981
Change in discount on loss reserves ceded under retroactive reinsurance	18	17	57	56
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 6	$ 1	$ 10	$ 18