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Segment Information (Income Before and After Federal Income Tax) (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2023 | Mar. 31, 2022
Segment Reporting Information [Line Items] |  |
Net investment income earned | $ 91,506 | $ 72,602
Net realized and unrealized investment gains (losses) | 3,344 | (40,352)
Total investment segment income, before federal income tax | 94,850 | 32,250
Tax on investments segment income | 19,156 | 5,613
Total investment segment income, after federal income tax | 75,694 | 26,637
Standard Commercial Lines |  |
Segment Reporting Information [Line Items] |  |
Underwriting income (loss), before federal income tax | 38,921 | 42,384
Underwriting income (loss), after federal income tax | $ 30,748 | $ 33,483
Combined ratio | 94.70% | 93.60%
ROE Contribution | 5.10% | 5.00%
Standard Personal Lines |  |
Segment Reporting Information [Line Items] |  |
Underwriting income (loss), before federal income tax | $ (13,073) | $ 6,520
Underwriting income (loss), after federal income tax | $ (10,328) | $ 5,151
Combined ratio | 116.00% | 91.00%
ROE Contribution | (1.70%) | 0.80%
E&S Lines |  |
Segment Reporting Information [Line Items] |  |
Underwriting income (loss), before federal income tax | $ 13,335 | $ 6,925
Underwriting income (loss), after federal income tax | $ 10,535 | $ 5,471
Combined ratio | 85.00% | 91.10%
ROE Contribution | 1.80% | 0.80%
Investments |  |
Segment Reporting Information [Line Items] |  |
ROE Contribution | 12.20% | 8.70%

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