Liabilities for Losses and Loss Expenses (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Liability for Claims and Claims Adjustment Expense [Abstract]
Balance at January 1	$ 1,121,045,758	$ 1,077,620,000
Less reinsurance recoverable	(451,184,000)	(451,261,000)
Cumulative effect of adoption of updated accounting guidance for credit losses at January 1	1,132,000	0
Net balance at January 1	670,994,000	626,359,000
Incurred related to [Abstract]
Current year	461,799,000	445,855,000
Prior years	(15,775,000)	(30,609,000)
Total incurred	446,024,000	415,246,000
Paid related to [Abstract]
Current year	230,214,000	209,051,000
Prior years	204,842,000	170,129,000
Total paid	435,056,000	379,180,000
Net balance at end of period	681,962,000	662,425,000
Plus reinsurance recoverable	431,392,000	445,701,000
Balance at end of period	$ 1,113,354,318	$ 1,108,126,000
Percentage of development	2.40%	4.90%