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Statements of Cash Flows - Schedule of Cash Flow Supplemental Disclosures (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Cash paid (received) during the period for: |  |  |
Interest | $ 28,532 | $ 28,359 | $ 26,639
Federal income tax | 49,000 | 79,702 | 75,000
Cash paid for amounts included in the measurement of lease liabilities: |  |  |
Operating cash flows from operating leases | 8,413 | 7,409 | 8,148
Operating cash flows from financing leases | 234 | 66 | 46
Financing cash flows from finance leases | 2,629 | 2,666 | 2,438
Non-cash items: |  |  |
Conversion of alternative investments to equity securities | 0 | 50,253 | 0
Assets acquired under finance lease arrangements | 6,275 | 1,584 | 707
Assets acquired under operating lease arrangements | 11,684 | 5,885 | 16,649
Non-cash purchase of property and equipment | 53 | 242 | 70
Fixed income |  |  |
Non-cash items: |  |  |
Corporate actions related to securities | 43,558 | 22,741 | 38,106
Equity securities |  |  |
Non-cash items: |  |  |
Corporate actions related to securities | 29,250 | 0 | 0
Conversion of AFS fixed income securities to equity securities | $ 0 | $ 0 | $ 1,463

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