| **Legal Proceedings and Contingent Liabilities**            | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
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| **Legal Proceedings and Contingent Liabilities [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Legal Proceedings and Contingent Liabilities                | Legal Proceedings and Contingent LiabilitiesInsurance Brokerage Antitrust LitigationIn August 2005, CNAF and certain insurance subsidiaries were joined as defendants, along with other insurers and brokers, in multidistrict litigation pending in the United States District Court for the District of New Jersey, In re Insurance Brokerage Antitrust Litigation, Civil No. 04-5184 (GEB). The plaintiffs' consolidated class action complaint alleged bid rigging and improprieties in the payment of contingent commissions in connection with the sale of insurance. After various motions and preliminary court rulings providing for further proceedings, all parties executed final settlement documents and the plaintiffs filed a motion for preliminary approval of the settlement in May 2011. In June 2011, the Court entered an order preliminarily approving the settlement. A fairness hearing was held in September 2011 to determine final approval of the settlement. The Court took the matter under advisement and will issue a ruling in due course.  As currently structured, the settlement will not have a material impact on the Company's results of operations. In addition, the Company does not believe it has any material ongoing exposure relating to this matter.Other LitigationThe Company is also a party to routine litigation incidental to its business, which, based on the facts and circumstances currently known, is not material to the operations or financial condition of the Company. |

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Legal Proceedings and Contingent Liabilities [Abstract]
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The entire disclosure for legal proceedings, legal contingencies, litigation, regulatory and environmental matters and other contingencies.
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