Income Taxes (Significant components of the Company's deferred tax assets and liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets:
Property and casualty claim and claim adjustment expense reserves	$ 202	$ 178
Unearned premium reserves	213	198
Policyholder reserves	160	75
Deferred Revenue	62	64
Employee benefits	23	35
Deferred retroactive reinsurance benefit	88	89
Net unrealized losses	418	706
Other assets	111	116
Gross deferred tax assets	1,277	1,461
Deferred Tax Liabilities:
Investment valuation differences	83	59
Deferred acquisition costs	126	113
Net unrealized gains	0	0
Software and hardware	18	21
Other liabilities	34	17
Gross deferred tax liabilities	261	210
Net deferred tax asset	$ 1,016	$ 1,251