Summary of Significant Accounting Policies - Catastrophe Exposures - Additional Information (Details) - USD ($) $ in Millions	Jan. 01, 2023	May 01, 2022	Jan. 01, 2022
California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		$ 750	$ 600
First-dollar retention		25	25
California Earthquake | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	$ 700
First-dollar retention	25
Outside of California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		775	625
First-dollar retention		25	25
Outside of California Earthquake | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	700
First-dollar retention	50
Other Perils including Wind
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		625	475
First-dollar retention		25	25
Other Perils including Wind | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	600
First-dollar retention	$ 50
Catastrophe
Liability For Catastrophe Claims [Line Items]
First-dollar retention			$ 25
Additional catastrophe reinsurance		$ 150