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Segment Information (Reconciliation of Segment Results to Income Before Federal Income Tax (Details)) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2023 | Mar. 31, 2022
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Investment income | $ 94,850 | $ 32,250
Interest expense | (7,166) | (7,168)
Corporate expenses | (12,108) | (11,021)
Income before federal income tax | 114,759 | 69,890
Preferred stock dividends | (2,300) | (2,300)
Income available to common stockholders, before federal income tax | 112,459 | 67,590
Standard Commercial Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income (loss), before federal income tax | 38,921 | 42,384
Standard Personal Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income (loss), before federal income tax | (13,073) | 6,520
E&S Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income (loss), before federal income tax | 13,335 | 6,925
Operating Segments |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income (loss), total all segments | $ 134,033 | $ 88,079

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