Reserves for Losses and Loss Settlement Expenses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross liability for losses and loss settlement expenses at beginning of year	$ 1,638,755	$ 1,497,274
Ceded losses and loss settlement expenses	(191,640)	(146,875)
Net liability for losses and loss settlement expenses at beginning of year	1,447,115	1,350,399
Losses and loss settlement expenses incurred for claims occurring during
Current year	177,197	701,664
Prior years	2,449	67,750
Total incurred	179,646	769,414
Losses and loss settlement expense payments for claims occurring during
Current year	18,625	191,899
Prior years	123,225	480,800
Total paid	141,850	672,699
Net liability for losses and loss settlement expenses at end of period	1,484,911	1,447,115
Ceded losses and loss settlement expenses	205,974	191,640
Gross liability for losses and loss settlement expenses at end of period	$ 1,690,885	$ 1,638,755