Loss And Loss Adjustment Expense Reserves - Average Annual Percentage Payout of Incurred Claims by Age (Details)	Dec. 31, 2021
Property insurance product line, automobile
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	61.40%
Short-duration insurance contracts, historical claims duration, year two	17.70%
Short-duration insurance contracts, historical claims duration, year three	8.80%
Short-duration insurance contracts, historical claims duration, year four	5.30%
Short-duration insurance contracts, historical claims duration, year five	2.80%
Short-duration insurance contracts, historical claims duration, year six	1.10%
Short-duration insurance contracts, historical claims duration, year seven	0.50%
Short-duration insurance contracts, historical claims duration, year eight	0.20%
Short-duration insurance contracts, historical claims duration, year nine	0.10%
Short-duration insurance contracts, historical claims duration, year ten	0.00%
Property insurance product line, homeowners'
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration insurance contracts, historical claims duration, year one	67.80%
Short-duration insurance contracts, historical claims duration, year two	21.80%
Short-duration insurance contracts, historical claims duration, year three	4.00%
Short-duration insurance contracts, historical claims duration, year four	2.30%
Short-duration insurance contracts, historical claims duration, year five	1.20%
Short-duration insurance contracts, historical claims duration, year six	0.50%
Short-duration insurance contracts, historical claims duration, year seven	0.70%
Short-duration insurance contracts, historical claims duration, year eight	0.20%
Short-duration insurance contracts, historical claims duration, year nine	0.10%
Short-duration insurance contracts, historical claims duration, year ten	0.00%