Summary of Significant Accounting Policies - Catastrophe Exposures - Additional Information (Details) - USD ($) $ in Millions	May 01, 2022	Jan. 01, 2022
California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	$ 750	$ 600
First-dollar retention	25	25
Outside of California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	775	625
First-dollar retention	25	25
Other Perils including Wind
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	625	475
First-dollar retention	25	25
Catastrophe
Liability For Catastrophe Claims [Line Items]
First-dollar retention	25	$ 25
Additional catastrophe reinsurance	$ 150