Premiums and Reinsurance Related Information - Schedule of A.M. Best Financial Strength Rating and Percent of Total Reinsurance Recoverable (Details) - Reinsurance Recoverable Including Reinsurance Premium Paid - Reinsurer Concentration Risk	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	100.00%	100.00%
AM Best, A Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	100.00%	100.00%
Renaissance Reinsurance U.S. Inc | AM Best, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	30.10%	29.80%
Endurance Assurance Corporation | AM Best, A+ Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	23.70%	23.80%
Markel Global Reinsurance Company | AM Best, A Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	19.00%	20.80%
American Family Connect Property and Casualty Insurance Company | AM Best, A Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	8.80%	7.50%
Ascot Bermuda Limited | AM Best, A Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	7.70%	9.40%
All other reinsurers | AM Best, A Rating
Ceded Credit Risk [Line Items]
Reinsurance recoverables (percent)	10.70%	8.70%