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v3.24.0.1

Segment Information (Revenue From Continuing Operations by Segment) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | $ 3,827,606 | $ 3,373,380 | $ 3,017,253
Other income | 19,402 | 11,335 | 17,723
Net investment income earned | 388,650 | 288,155 | 326,589
Net realized and unrealized investment gains (losses) | (3,552) | (114,808) | 17,599
Total investment revenues, before federal income tax | 385,098 | 173,347 | 344,188
Total revenues | 4,232,106 | 3,558,062 | 3,379,164
Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Total revenues | 3,088,952 | 2,749,338 | 2,459,941
Standard Personal Lines |  |  |
Revenue from External Customer [Line Items] |  |  |
Total revenues | 367,414 | 301,221 | 295,226
E&S Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Total revenues | 390,642 | 334,156 | 279,809
Commercial Automobile [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 586,267 | 495,647 | 436,412
Workers Compensation [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 333,669 | 335,955 | 306,428
General Liability [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 1,020,362 | 902,428 | 807,158
Commercial Property [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 916,140 | 812,306 | 724,398
Business Owners' Policies [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 140,547 | 124,474 | 110,622
Bonds Segment [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 46,215 | 43,354 | 35,762
Other Commercial [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 28,584 | 25,655 | 23,105
Personal Automobile [Member] | Standard Personal Lines |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 200,027 | 162,899 | 163,007
Homeowners [Member] | Standard Personal Lines |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 154,828 | 128,222 | 122,526
Other Personal [Member] | Standard Personal Lines |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 10,358 | 8,284 | 8,026
Casualty Insurance Product Line [Member] | E&S Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 261,144 | 233,086 | 197,779
Property Insurance [Member] | E&S Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Net premiums earned | 129,465 | 101,070 | 82,030
Miscellaneous Income [Member] | Standard Commercial Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Other income | 17,168 | 9,519 | 16,056
Miscellaneous Income [Member] | Standard Personal Lines |  |  |
Revenue from External Customer [Line Items] |  |  |
Other income | 2,201 | 1,816 | 1,667
Miscellaneous Income [Member] | E&S Lines [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Other income | $ 33 | $ 0 | $ 0

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