Statements of Cash Flows - Schedule of Cash Flow Supplemental Disclosures (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash paid (received) during the period for:
Interest	$ 14,209	$ 14,164
Federal income tax	46,000	34,000
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	3,884	4,038
Operating cash flows from financing leases	65	20
Financing cash flows from finance leases	1,266	1,231
Non-cash items:
Assets acquired under finance lease arrangements	5,947	0
Assets acquired under operating lease arrangements	10,257	4,509
Non-cash purchase of property and equipment	9	0
Fixed income securities, AFS
Non-cash items:
Corporate actions related to securities	10,250	23,150
Equity securities
Non-cash items:
Corporate actions related to securities	$ 29,250	$ 0