Liabilities for Losses and Loss Expenses (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Liability for Claims and Claims Adjustment Expense [Abstract]
Balance at January 1	$ 1,077,620,301	$ 962,007,000
Less reinsurance recoverable	(451,261,000)	(404,818,000)
Net balance at January 1	626,359,000	557,189,000
Incurred related to [Abstract]
Current year	134,432,000	127,433,000
Prior years	(16,549,000)	(8,213,000)
Total incurred	117,883,000	119,220,000
Paid related to [Abstract]
Current year	40,293,000	35,584,000
Prior years	76,088,000	65,192,000
Total paid	116,381,000	100,776,000
Net balance at end of period	627,861,000	575,633,000
Plus reinsurance recoverable	443,726,000	421,346,000
Balance at end of period	$ 1,071,587,385	$ 996,979,000
Percentage of development	2.60%	1.50%