Organization	12 Months Ended
Dec. 31, 2011
Organization [Abstract]
Organization	Note 1. Organization Selective Insurance Group, Inc., through its subsidiaries, (collectively referred to as "we," "us," or "our") offers standard and excess and surplus lines ("E&S") property and casualty insurance products. Selective Insurance Group, Inc. (referred to as the "Parent") was incorporated in New Jersey in 1977 and its main offices are located in Branchville, New Jersey. The Parent's common stock is publicly traded on the NASDAQ Global Select Market under the symbol "SIGI." We have provided a glossary of terms as Exhibit 99.1 to this Form 10-K, which defines certain industry-specific and other terms that are used in this Form 10-K. In August 2011, we purchased the renewal rights to an E&S book of business and, effective as of December 31, 2011, we purchased Montpelier U.S. Insurance Company ("MUSIC") which is now our eighth insurance subsidiary. Our eight insurance subsidiaries are collectively referred to as the "Insurance Subsidiaries". MUSIC, an E&S carrier, is authorized to write business in all 50 states and the District of Columbia, and provides us with a nationally-licensed platform to write contract binding authority E&S business. We classify our business into two operating segments: Insurance Operations, which sells property and casualty insurance products and services in both the standard and E&S markets; and Investments, which invests the premiums collected by our insurance operations.

Organization

12 Months Ended

Dec. 31, 2011

Note 1. Organization

Selective Insurance Group, Inc., through its subsidiaries, (collectively referred to as "we," "us," or "our") offers standard and excess and surplus lines ("E&S") property and casualty insurance products. Selective Insurance Group, Inc. (referred to as the "Parent") was incorporated in New Jersey in 1977 and its main offices are located in Branchville, New Jersey. The Parent's common stock is publicly traded on the NASDAQ Global Select Market under the symbol "SIGI." We have provided a glossary of terms as Exhibit 99.1 to this Form 10-K, which defines certain industry-specific and other terms that are used in this Form 10-K.

In August 2011, we purchased the renewal rights to an E&S book of business and, effective as of December 31, 2011, we purchased Montpelier U.S. Insurance Company ("MUSIC") which is now our eighth insurance subsidiary. Our eight insurance subsidiaries are collectively referred to as the "Insurance Subsidiaries". MUSIC, an E&S carrier, is authorized to write business in all 50 states and the District of Columbia, and provides us with a nationally-licensed platform to write contract binding authority E&S business.

We classify our business into two operating segments:

Insurance Operations, which sells property and casualty insurance products and services in both the standard and E&S markets; and
Investments, which invests the premiums collected by our insurance operations.