Insurance Liabilities - Liability for unpaid losses and loss adjustment expenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 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	$ 76,739	$ 78,981	$ 79,026	$ 77,720
Reinsurance recoverable	(33,583)	(34,866)	(35,213)	(34,431)
Net Liability for unpaid loss and loss adjustment expenses, beginning of period	43,156	44,115	43,813	43,289
Losses and loss adjustment expenses incurred:
Current year	4,373	4,467	12,020	12,262
Prior years, excluding discount and amortization of deferred gain	(112)	(153)	(537)	(166)
Prior years, discount charge (benefit)	36	83	78	99
Prior years, amortization of deferred gain on retroactive reinsurance	(23)	(13)	(37)	(107)
Total losses and loss adjustment expenses incurred	4,274	4,384	11,524	12,088
Losses and loss adjustment expenses paid:
Current year	(1,132)	(1,147)	(2,289)	(2,370)
Prior years	(2,673)	(2,449)	(8,844)	(8,653)
Total losses and loss adjustment expenses paid	(3,805)	(3,596)	(11,133)	(11,023)
Other changes:
Foreign exchange effect	(1,031)	(414)	(1,827)	(57)
Retroactive reinsurance adjustment (net of discount)	101	159	318	351
Total other changes	(930)	(255)	(1,509)	294
Net liability for unpaid losses and loss adjustment expenses	42,695	44,648	42,695	44,648
Reinsurance recoverable	32,824	34,626	32,824	34,626
Total	75,519	79,274	75,519	79,274
Change in discount on loss reserves ceded under retroactive reinsurance	17	22	74	78
National Indemnity Company
Losses and loss adjustment expenses incurred:
Prior years, amortization of deferred gain on retroactive reinsurance	$ 5	$ 5	$ 15	$ 23