XML 136 R104.htm IDEA: XBRL DOCUMENT 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