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Segment Information (Revenue From Continuing Operations by Segment) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2010 | Jun. 30, 2010 | Mar. 31, 2010 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Total net premiums earned | $ 373,427 | $ 358,963 | $ 355,580 | $ 351,343 | $ 353,497 | $ 354,709 | $ 352,190 | $ 356,202 | $ 1,439,313 | $ 1,416,598 | $ 1,431,047
Other income |  |  |  |  |  |  |  |  | 8,479 | 9,398 | 10,470
Total Insurance Operations revenues |  |  |  |  |  |  |  |  | 1,447,382 | 1,425,828 | 1,441,487
Net investment income | 28,839 | 35,786 | 39,345 | 43,473 | 41,471 | 32,986 | 36,545 | 34,706 | 147,443 | 145,708 | 118,471
Net realized gain on investments |  |  |  |  |  |  |  |  | 2,240 | (7,083) | (45,970)
Total investment income, before federal income tax |  |  |  |  |  |  |  |  | 149,683 | 138,625 | 72,501
Total all segments |  |  |  |  |  |  |  |  | 1,597,065 | 1,564,453 | 1,513,988
Total revenues |  |  |  |  |  |  |  |  | 1,597,475 | 1,564,621 | 1,514,018
Commercial Automobile [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 279,610 | 291,495 | 300,562
Workers Compensation [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 259,354 | 252,441 | 263,490
General Liability [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 344,682 | 336,475 | 362,479
Commercial Property [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 192,989 | 199,252 | 197,665
Business Owners Policies [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 66,225 | 65,260 | 62,638
Bonds Segment [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 18,910 | 19,243 | 18,455
Other Commercial [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 13,091 | 10,116 | 9,663
Total Commercial Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 1,174,861 | 1,174,282 | 1,214,952
Personal Automobile [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 148,824 | 141,962 | 133,320
Homeowners [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 102,764 | 87,862 | 73,076
Other Personal [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 12,864 | 12,492 | 9,699
Total Personal Lines [Member] |  |  |  |  |  |  |  |  |  |  |
Total net premiums earned |  |  |  |  |  |  |  |  | 264,452 | 242,316 | 216,095
Miscellaneous Income [Member] |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  | 8,069 | 9,230 | 10,440
Other Income [Member] |  |  |  |  |  |  |  |  |  |  |
Other income |  |  |  |  |  |  |  |  | $ 410 | $ 168 | $ 30

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- Definition Revenue from insurance services, including net premiums earned, gain on sale of insurance block, agency management fees and insurance contract fees and commissions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1,4) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
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- Definition Premiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 + Details
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