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v3.19.3.a.u2

Segment Information (Revenue From Continuing Operations by Segment) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned | $ 668,359 | $ 653,620 | $ 642,619 | $ 632,573 | $ 625,288 | $ 614,277 | $ 604,836 | $ 591,828 | $ 2,597,171 | $ 2,436,229 | $ 2,291,027
Other income | 3,820 | 3,162 | 3,053 | 2,320 | 1,542 | 2,538 | 3,179 | 2,179 | 12,355 | 9,438 | 10,716
Net investment income | 57,594 | 55,826 | 58,505 | 50,618 | 54,109 | 52,443 | 45,553 | 43,231 | 222,543 | 195,336 | 161,882
Total net realized and unrealized gains (losses) | (873) | (2,183) | 4,027 | 13,451 | (37,935) | (4,787) | (1,652) | (10,549) | 14,422 | (54,923) | 6,359
Total investment revenues |  |  |  |  |  |  |  |  | 236,965 | 140,413 | 168,241
Total revenues | $ 728,900 | $ 710,425 | $ 708,204 | $ 698,962 | $ 643,004 | $ 664,471 | $ 651,916 | $ 626,689 | 2,846,491 | 2,586,080 | 2,469,984
Standard Commercial Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  | 10,889 | 8,180 | 9,488
Total revenues |  |  |  |  |  |  |  |  | 2,060,503 | 1,920,402 | 1,797,987
Standard Commercial Lines [Member] | Commercial Automobile [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 554,256 | 493,093 | 442,818
Standard Commercial Lines [Member] | Workers Compensation [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 311,370 | 317,616 | 317,982
Standard Commercial Lines [Member] | General Liability [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 669,895 | 616,187 | 569,217
Standard Commercial Lines [Member] | Commercial Property [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 353,834 | 329,660 | 311,932
Standard Commercial Lines [Member] | Business Owners' Policies [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 105,252 | 103,412 | 100,266
Standard Commercial Lines [Member] | Bonds Segment [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 35,726 | 33,991 | 29,086
Standard Commercial Lines [Member] | Other Commercial [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 19,281 | 18,263 | 17,198
Standard Personal Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  | 1,466 | 1,257 | 1,228
Total revenues |  |  |  |  |  |  |  |  | 309,205 | 305,698 | 290,929
Standard Personal Lines [Member] | Personal Automobile [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 172,606 | 168,250 | 153,147
Standard Personal Lines [Member] | Homeowners [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 127,543 | 128,961 | 129,699
Standard Personal Lines [Member] | Other Personal [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 7,590 | 7,230 | 6,855
E&S Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  | 0 | 1 | 0
Total revenues |  |  |  |  |  |  |  |  | 239,818 | 219,567 | 212,827
E&S Lines [Member] | Casualty Insurance Product Line [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | 182,864 | 164,313 | 157,366
E&S Lines [Member] | Property Insurance [Member] |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 56,954 | $ 55,253 | $ 55,461

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