Income Taxes (Details) - Deferred Tax Asset and Liability - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Deferred tax assets, claims and claim adjustment expense reserves	$ 601	$ 575
Deferred tax assets, unearned premium reserves	603	560
Deferred tax assets, compensation-related liabilities	35	110
Deferred tax assets, net operating losses	101	87
Deferred tax assets, other	152	180
Total gross deferred tax assets	1,492	1,512
Less: valuation allowance	23	21
Adjusted gross deferred tax assets	1,469	1,491
Deferred tax liabilities, deferred acquisition costs	479	445
Deferred tax liabilities, investments	940	1,225
Deferred tax liabilities, depreciation	112	130
Deferred tax liabilities, other	227	249
Total gross deferred tax liabilities	1,758	2,049
Net deferred tax liability	$ 289	$ 558