Summary of Significant Accounting Policies - Catastrophe Exposures - Additional Information (Details) - USD ($) $ in Millions	Jun. 01, 2023	Jan. 01, 2023
California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	$ 850	$ 700
First-dollar retention	25	25
Outside of California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	850	700
First-dollar retention	50	50
Other Perils including Wind
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	750	600
First-dollar retention	50	$ 50
Catastrophe
Liability For Catastrophe Claims [Line Items]
Additional catastrophe reinsurance	$ 150