Income Taxes (Significant components of the Company's deferred tax assets and liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Deferred Tax Assets:
Property and casualty claim and claim adjustment expense reserves	$ 234	$ 202
Unearned premium reserves	225	213
Policyholder reserves	0	160
Deferred revenue	59	62
Employee benefits	13	23
Deferred retroactive reinsurance benefit	89	88
Net unrealized losses	494	418
Other assets	107	111
Gross deferred tax assets	1,221	1,277
Deferred Tax Liabilities:
Investment valuation differences	130	83
Deferred acquisition costs	140	126
Policyholder reserves	48	0
Software and hardware	17	18
Other liabilities	36	34
Gross deferred tax liabilities	371	261
Net deferred tax asset	$ 850	$ 1,016