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Segment Information - Schedule of Reconciliation of Segment Results to Income (Loss) Before Federal Income Tax (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Investment income | $ 109,939 | $ 92,270 | $ 216,153 | $ 187,120
Interest expense | (7,202) | (7,258) | (14,383) | (14,424)
Corporate expenses | (9,154) | (9,329) | (24,652) | (21,437)
Income (loss), before federal income tax | (80,098) | 74,157 | 22,468 | 188,916
Preferred stock dividends | (2,300) | (2,300) | (4,600) | (4,600)
Income (loss) available to common stockholders, before federal income tax | (82,398) | 71,857 | 17,868 | 184,316
Standard Commercial Lines |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Underwriting income (loss) | (160,881) | 22,146 | (150,500) | 61,067
Standard Personal Lines |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Underwriting income (loss) | (19,301) | (23,060) | (24,636) | (36,133)
E&S Lines |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Underwriting income (loss) | 6,501 | (612) | 20,486 | 12,723
Investments |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Investment income | 109,939 | 92,270 | 216,153 | 187,120
Operating Segments |  |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |  |
Total all segments | $ (63,742) | $ 90,744 | $ 61,503 | $ 224,777

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