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Segment Information (Income Before Federal Income Tax) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Segment Reporting Information [Line Items] |  |  |  |
Total investment revenues | $ 32,369 | $ 49,523 | $ 106,979 | $ 133,588
Tax on investment income | 7,614 | 13,858 | 26,186 | 36,374
Total investment income after federal income tax | 24,755 | 35,665 | 80,793 | 97,214
Standard Commercial Lines [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting gain (loss), before federal income tax | $ 44,027 | $ 27,771 | $ 109,304 | $ 39,844
GAAP combined ratio | 88.70% | 92.10% | 90.30% | 96.20%
Statutory combined ratio | 88.40% | 90.90% | 89.40% | 95.50%
Standard Personal Lines [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting gain (loss), before federal income tax | $ 2,826 | $ 8,037 | $ (4,295) | $ 95
GAAP combined ratio | 96.10% | 89.20% | 102.00% | 100.00%
Statutory combined ratio | 95.00% | 88.90% | 101.70% | 99.90%
Excess And Surplus Operations [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Underwriting gain (loss), before federal income tax | $ (2,022) | $ (1,371) | $ (5,033) | $ (433)
GAAP combined ratio | 104.40% | 103.80% | 104.00% | 100.40%
Statutory combined ratio | 101.10% | 102.90% | 101.80% | 100.30%

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- Definition The statutory combined ratio (expressed as a percentage) is the sum of: (i) the loss and loss expense ratio; (ii) the underwriting ratio; and (iii) the dividend ratio. The loss and loss expense ratio as well as the dividend ratio is calculated by dividing loss and loss expenses, as well as dividends to policyholders, by net premiums earned. The underwriting expense ratio is calculated by dividing underwriting expenses by net premiums written. + References No definition available. + Details
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