Statements of Cash Flows - Schedule of Cash Flow Supplemental Disclosures (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Cash paid (received) during the period for:
Interest	$ 26,013	$ 14,278
Federal income tax	81,000	83,269
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	5,221	5,053
Operating cash flows from financing leases	74	139
Financing cash flows from finance leases	1,337	1,403
Non-cash items:
Assets acquired under operating lease arrangements	265	2,062
Non-cash purchase of property and equipment	18	13
Equity securities
Non-cash items:
Conversion of AFS fixed income securities to equity securities	0	736
Corporate actions related to fixed income securities, available-for-sale ("AFS")
Non-cash items:
Corporate actions related to fixed income securities, available-for-sale ("AFS")	20,879	39,742
Alternative investments
Non-cash items:
Conversion of commercial mortgage loan ("CML") to alternative investment	$ 0	$ 3,300

Cash Paid for Amounts Included in the Measurement of Lease Liabilities

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Cash Paid (Received) During the Period

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Conversion of AFS fixed income securities to equity securities

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Conversion Of Commercial Mortgage Loan To Alternative Investment

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Amount of interest paid on finance lease liability.

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Amount of cash outflow for principal payment on finance lease.

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Amount, after refund, of cash paid to foreign, federal, state, and local jurisdictions as income tax.

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Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

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The amount of fixed assets that an Entity acquires in a noncash (or part noncash) acquisition. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

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