Income Taxes (Details) - Deferred Tax Asset and Liability - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Deferred tax assets, investments	$ 999	$ 0
Deferred tax assets, claims and claim adjustment expense reserves	660	601
Deferred tax assets, unearned premium reserves	673	603
Deferred tax assets, net operating losses	96	101
Deferred tax assets, other	262	187
Total gross deferred tax assets	2,690	1,492
Less: valuation allowance	27	23
Adjusted gross deferred tax assets	2,663	1,469
Deferred tax liabilities, claims and claim adjustment expense reserve discounting (transition rule)	58	77
Deferred tax liabilities, deferred acquisition costs	539	479
Deferred tax liabilities, investments	0	940
Deferred tax liabilities, intangibles	65	59
Deferred tax liabilities, depreciation	105	112
Deferred tax liabilities, other	19	91
Total gross deferred tax liabilities	786	1,758
Net deferred tax asset	$ 1,877
Net deferred tax (liability)		$ (289)