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v3.10.0.1

Segment Information (Revenue From Continuing Operations by Segment) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2018 | [1] | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | [1] | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned | $ 625,288 |  | $ 614,277 |  | $ 604,836 |  | $ 591,828 |  | $ 590,088 |  | $ 572,055 |  | $ 568,030 |  | $ 560,854 |  | $ 2,436,229 | $ 2,291,027 | $ 2,149,572
Other income | 1,542 |  | 2,538 |  | 3,179 |  | 2,179 |  | 2,190 |  | 1,994 |  | 3,291 |  | 3,241 |  | 9,438 | 10,716 | 8,881
Net investment income | 54,109 |  | 52,443 |  | 45,553 |  | 43,231 |  | 42,587 |  | 40,446 |  | 41,430 |  | 37,419 |  | 195,336 | 161,882 | 130,754
Total net realized and unrealized (losses) gains | (37,935) | [2] | (4,787) | [2] | (1,652) | [2] | (10,549) | [2] | (1,128) | [2] | 6,798 | [2] | 1,734 | [2] | (1,045) | [2] | (54,923) | 6,359 | (4,937)
Total investment revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 140,413 | 168,241 | 125,817
Total revenues | $ 643,004 |  | $ 664,471 |  | $ 651,916 |  | $ 626,689 |  | $ 633,737 |  | $ 621,293 |  | $ 614,485 |  | $ 600,469 |  | 2,586,080 | 2,469,984 | 2,284,270
Standard Commercial Lines [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,180 | 9,488 | 7,782
Total revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,920,402 | 1,797,987 | 1,673,265
Standard Commercial Lines [Member] | Commercial Automobile [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 493,093 | 442,818 | 398,942
Standard Commercial Lines [Member] | Workers Compensation [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 317,616 | 317,982 | 308,233
Standard Commercial Lines [Member] | General Liability [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 616,187 | 569,217 | 527,859
Standard Commercial Lines [Member] | Commercial Property [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 329,660 | 311,932 | 293,438
Standard Commercial Lines [Member] | Business Owners' Policies [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 103,412 | 100,266 | 97,754
Standard Commercial Lines [Member] | Bonds Segment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 33,991 | 29,086 | 23,227
Standard Commercial Lines [Member] | Other Commercial [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 18,263 | 17,198 | 16,030
Standard Personal Lines [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,257 | 1,228 | 1,098
Total revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 305,698 | 290,929 | 281,705
Standard Personal Lines [Member] | Personal Automobile [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 168,250 | 153,147 | 142,876
Standard Personal Lines [Member] | Homeowners [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 128,961 | 129,699 | 130,973
Standard Personal Lines [Member] | Other Personal [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,230 | 6,855 | 6,758
Excess And Surplus Operations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 0 | 1
Total revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 219,567 | 212,827 | 203,483
Excess And Surplus Operations [Member] | Casualty Insurance Product Line [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 164,313 | 157,366 | 151,638
Excess And Surplus Operations [Member] | Property Insurance Product Line [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 55,253 | $ 55,461 | $ 51,844
[1] | Results for the fourth quarter of 2017 include the impact of the $20.2 million write off of deferred tax assets required with the implementation of Tax Reform. See Note 13. "Federal Income Taxes" above for additional information.
[2] | Effective January 1, 2018, changes in unrealized gains and losses on our equity portfolio are recognized in income through "Net unrealized losses on equity securities" on our Consolidated Statements of Income, as a result of our adoption of ASU 2016-01. See Note 3. "Adoption of Accounting Pronouncements" above.

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