Consolidated Property Casualty Loss And Loss Expense Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition
Gross loss and loss expense reserves, January 1	$ 7,229	$ 6,677	$ 6,088
Less reinsurance recoverable	327	277	342
Net loss and loss expense reserves, January 1	6,902	6,400	5,746
Net incurred loss and loss expenses related to:
Current accident year	4,875	4,024	3,968
Prior accident years	(159)	(428)	(131)
Total incurred	4,716	3,596	3,837
Net paid loss and loss expenses related to:
Current accident year	1,592	1,379	1,493
Prior accident years	2,095	1,715	1,690
Total paid	3,687	3,094	3,183
Net loss and loss expense reserves, December 31	7,931	6,902	6,400
Plus reinsurance recoverable	405	327	277
Gross loss and loss expense reserves, December 31	$ 8,336	$ 7,229	$ 6,677