Summary of Significant Accounting Policies - Catastrophe Exposures - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2022	Dec. 31, 2021
California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		$ 500
First-dollar retention		25
California Earthquake | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	$ 600
First-dollar retention	25
Non-California Earthquake
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		525
First-dollar retention		25
Non-California Earthquake | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	625
First-dollar retention	25
Earthquake
Liability For Catastrophe Claims [Line Items]
First-dollar retention		25
Earthquake | Subsequent Event
Liability For Catastrophe Claims [Line Items]
First-dollar retention	25
Other Perils
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance		375
First-dollar retention		$ 25
Other Perils | Subsequent Event
Liability For Catastrophe Claims [Line Items]
Catastrophe reinsurance	475
First-dollar retention	$ 25