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Related Party Transactions (Narrative) (Details) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Equity ownership percentage of director of parent | 10.00% |  |
Direct premiums written | $ 1,955,667,000 | $ 1,725,393,000 | $ 1,634,415,000
Premiums paid to Rue Insurance for insurance coverage | 200,000 | 200,000 | 300,000
Contributions to the Selective Group Foundation | 400,000 | 400,000 | 400,000
Related Party Insurance Agency [Member] |  |  |
Direct premiums written | 7,700,000 | 7,800,000 | 7,200,000
Commissions paid to Rue Insurance | $ 1,300,000 | $ 1,200,000 | $ 1,300,000

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- Definition The minimum percentage of the equity of an independent insurance agency owned by a director of the Parent. + References No definition available. + Details
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- Definition The amount of contributions made to a related party private foundation. + References No definition available. + Details
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- Definition Premiums written directly by insurer for all property and casualty insurance before adding contracts assumed from other insurers or subtracting any amounts assumed by other insurers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: 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FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(1) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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- Definition The amount of cash paid for commissions during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -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. + Details
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