Consolidated Property Casualty Loss And Loss Expense Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 28, 2019
Business Acquisition
Gross loss and loss expense reserves, January 1	$ 6,677	$ 6,088	$ 5,646
Less reinsurance recoverable	277	342	238
Net loss and loss expense reserves, January 1	6,400	5,746	5,408
Net incurred loss and loss expenses related to:
Current accident year	4,024	3,968	3,600
Prior accident years	(428)	(131)	(248)
Total incurred	3,596	3,837	3,352
Net paid loss and loss expenses related to:
Current accident year	1,379	1,493	1,462
Prior accident years	1,715	1,690	1,798
Total paid	3,094	3,183	3,260
Net loss and loss expense reserves, December 31	6,902	6,400	5,746
Plus reinsurance recoverable	327	277	342
Gross loss and loss expense reserves, December 31	$ 7,229	$ 6,677	$ 6,088
Cincinnati Global
Business Acquisition
Net loss and loss expense reserves related to acquisition of Cincinnati Global at February 28, 2019				$ 246