Reserves for Unpaid Losses and Loss Adjustment Expenses (Activity in the Reserves for Unpaid Losses and Loss Adjustment Expense) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Reserves for Unpaid Losses and Loss Adjustment Expenses [Abstract]
Balance at January 1	$ 789,768	$ 620,355
Less reinsurance recoverable	357,200	274,275
Net balance at January 1	432,568	346,080
Incurred related to:
Current year	207,121	253,319
Loss portfolio transfer	0	21,700
Prior years	2,553	33,259
Total incurred	209,674	308,278
Paid related to:
Current year	64,292	67,146
Loss portfolio transfer	0	21,700
Prior years	130,623	177,325
Total paid	194,915	266,171
Net balance at June 30	447,327	388,187
Plus reinsurance recoverable	368,054	367,704
Balance at June 30	$ 815,381	$ 755,891