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v3.10.0.1

Segment Information (Revenue by Segment) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | $ 614,277 | $ 572,055 | $ 1,810,941 | $ 1,700,939
Other income | 2,538 | 1,994 | 7,896 | 8,526
Net investment income | 52,443 | 40,446 | 141,227 | 119,295
Net realized and unrealized investment (losses) gains | (4,787) | 6,798 | (16,988) | 7,487
Total investment revenues | 47,656 | 47,244 | 124,239 | 126,782
Total revenues | 664,471 | 621,293 | 1,943,076 | 1,836,247
Standard Commercial Lines [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Other income | 2,228 | 1,712 | 6,936 | 7,588
Total revenues | 483,284 | 446,962 | 1,429,368 | 1,334,846
Standard Commercial Lines [Member] | Commercial Automobile [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 124,862 | 111,711 | 365,197 | 327,156
Standard Commercial Lines [Member] | Workers Compensation [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 78,784 | 77,580 | 237,628 | 236,366
Standard Commercial Lines [Member] | General Liability [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 154,974 | 141,059 | 457,805 | 422,546
Standard Commercial Lines [Member] | Commercial Property [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 83,056 | 78,151 | 245,544 | 232,594
Standard Commercial Lines [Member] | Business Owners' Policies [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 25,994 | 25,019 | 77,414 | 74,853
Standard Commercial Lines [Member] | Bonds Segment [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 8,778 | 7,420 | 25,247 | 20,904
Standard Commercial Lines [Member] | Other Commercial [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 4,608 | 4,310 | 13,597 | 12,839
Standard Personal Lines [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Other income | 310 | 282 | 959 | 938
Total revenues | 77,467 | 72,883 | 228,049 | 216,412
Standard Personal Lines [Member] | Personal Automobile [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 42,772 | 38,612 | 125,024 | 113,225
Standard Personal Lines [Member] | Homeowners [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 32,293 | 32,215 | 96,717 | 97,382
Standard Personal Lines [Member] | Other Personal [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 2,092 | 1,774 | 5,349 | 4,867
Excess And Surplus Operations [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Other income | 0 | 0 | 1 | 0
Total revenues | 56,064 | 54,204 | 161,420 | 158,207
Excess And Surplus Operations [Member] | Casualty Insurance Product Line [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | 42,179 | 40,090 | 120,098 | 117,056
Excess And Surplus Operations [Member] | Property Insurance Product Line [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total net premiums earned | $ 13,885 | $ 14,114 | $ 41,321 | $ 41,151

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