2.2.0.25falsefalse006001 - Disclosure - Nature of Businesstruefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) $FROM_Jan01_2010_TO_Dec31_2010http://www.sec.gov/CIK0001289592duration2010-01-01T00:00:002010-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2true0twgp_NatureOfBusinessAbstracttwgpfalsenadurationNature of Business.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNature of Business.falsefalseNature of Business [Abstract]3false0us-gaap_NatureOfOperationsus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Note 1—Nature of BusinessTower Group, Inc. (the “Company” or “Tower”) offers a broad range of commercial, personal and specialty property and casualty insurance products and services through its subsidiaries to businesses in various industries and to individuals. The Company's common stock is publicly traded on the NASDAQ Global Select Market under the symbol “TWGP”.On July 1, 2010, the Company completed its acquisition of the Personal Lines Division of OneBeacon Insurance Group, Ltd. (“OBPL”). Subsequent to this acquisition, the Company changed the presentation of its business results, beginning July 1, 2010, by allocating the personal insurance business previously reported in the Brokerage Insurance segment along with the newly acquired OBPL business to a new Personal Insurance segment and merged the commercial business previously reported in the Brokerage Insurance and Specialty Business segments in a new Commercial Insurance segment. The Company's Insurance Services segment will also include fees earned by the management companies acquired as a part of the OBPL transaction. This change in presentation reflects the way management organizes the Company for making operating decisions and assessing profitability subsequent to the OBPL acquisition. This will result in the reporting of three operating segments. The prior period segment disclosures have been restated to conform to the current presentation.As a result of the changes described above, the Company now operates three business segments: Commercial Insurance, Personal Insurance and Insurance Services:<ul><li style="margin-left:36px;list-style:disc;">Commercial Insurance (“Commercial”) Segment offers a broad range of commercial lines property and casualty insurance products to small to mid-sized businesses distributed through a network of retail and wholesale agents on both an admitted and non-admitted basis. This segment also includes reinsurance solutions provided primarily to small insurance companies;</li><li style="margin-left:36px;list-style:disc;">Personal Insurance (“Personal”) Segment offers a broad range of personal lines property and casualty insurance products to individuals distributed through a network of retail and wholesale agents; and</li><li style="margin-left:36px;list-style:disc;">Insurance Services (“Services”) Segment provides underwriting, claims and reinsurance brokerage services to insurance companies.</li></ul>Note 1—Nature of BusinessTower Group, Inc. (the “Company” or “Tower”) offers a broad range of commercial, personal and specialtyfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes the nature of an entity's business, the major products or services it sells or provides and its principal markets, including the locations of those markets. If the entity operates in more than one business, the disclosure also indicates the relative importance of its operations in each business and the basis for the determination (for example, assets, revenues, or earnings). Disclosures about the nature of operations need not be quantified; relative importance could be conveyed by use of terms such as "predominately", "about equally", or "major and other". This element is also referred to as "Business Description".Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-6 -Paragraph 10 falsefalseNature of Business12Nature of BusinessUnKnownUnKnownUnKnownUnKnownfalsetrue