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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, 2022 | Mar. 31, 2021
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Investment income | $ 32,250 | $ 74,835
Interest expense | (7,168) | (7,359)
Corporate expenses | (11,021) | (9,554)
Income before federal income tax | 69,890 | 135,632
Preferred stock dividends | (2,300) | (2,453)
Income available to common stockholders, before tax | 67,590 | 133,179
Standard Commercial Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income, before federal income tax | $ 42,384 | $ 69,499
ROE Contribution | 5.00% | 8.60%
Standard Personal Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income, before federal income tax | $ 6,520 | $ 7,695
ROE Contribution | 0.80% | 1.00%
E&S Lines |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Underwriting income, before federal income tax | $ 6,925 | $ 516
ROE Contribution | 0.80% | 0.10%
Investments |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
ROE Contribution | 8.70% | 8.90%
Operating Segments |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |
Total income, before federal income tax all segments | $ 88,079 | $ 152,545

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