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Segment Information - Schedule of Income (Loss) Before and After 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 Information [Line Items] |  |  |  |
Net investment income earned | $ 108,642 | $ 97,696 | $ 216,491 | $ 189,202
Net realized and unrealized investment gains (losses) | 1,297 | (5,426) | (338) | (2,082)
Total investments segment income, before federal income tax | 109,939 | 92,270 | 216,153 | 187,120
Tax on investments segment income | 22,652 | 18,745 | 44,518 | 37,901
Total investments segment income, after federal income tax | 87,287 | 73,525 | 171,635 | 149,219
Standard Commercial Lines |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting income (loss), before federal income tax | (160,881) | 22,146 | (150,500) | 61,067
Underwriting income (loss), after federal income tax | $ (127,096) | $ 17,495 | $ (118,895) | $ 48,243
Combined ratio | 118.80% | 97.10% | 108.90% | 95.90%
ROE contribution | (18.40%) | 2.80% | (8.60%) | 4.10%
Standard Personal Lines |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting income (loss), before federal income tax | $ (19,301) | $ (23,060) | $ (24,636) | $ (36,133)
Underwriting income (loss), after federal income tax | $ (15,248) | $ (18,217) | $ (19,462) | $ (28,545)
Combined ratio | 118.10% | 126.50% | 111.70% | 121.40%
ROE contribution | (2.20%) | (2.90%) | (1.40%) | (2.40%)
E&S Lines |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting income (loss), before federal income tax | $ 6,501 | $ (612) | $ 20,486 | $ 12,723
Underwriting income (loss), after federal income tax | $ 5,136 | $ (483) | $ 16,184 | $ 10,051
Combined ratio | 94.60% | 100.70% | 91.20% | 93.00%
ROE contribution | 0.70% | (0.10%) | 1.20% | 0.80%
Investments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
ROE contribution | 12.50% | 12.60% | 12.50% | 12.50%
Total investments segment income, before federal income tax | $ 109,939 | $ 92,270 | $ 216,153 | $ 187,120

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