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Third Party Reinsurance (Tables) | 9 Months Ended
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Sep. 30, 2012
Reinsurance Disclosures [Abstract] |
Listing of OneBeacon's top reinsurers | The following table provides a listing of OneBeacon’s top reinsurers, based upon recoverable amounts, the percentage of total paid and unpaid reinsurance recoverables and the reinsurer’s A.M Best Company, Inc. (“A.M. Best”) rating.
Top Reinsurers (Millions) |  | Balance at September 30, 2012 |  | % of Total |  | A.M. Best Rating (1)
Hannover Ruckversich |  | $ | 6.4 |  |  | 15 | % |  | A+
Hartford Steam Boiler |  | 4.6 |  |  | 11 | % |  | A++
Munich Reinsurance America |  | 4.5 |  |  | 10 | % |  | A+
Platinum Underwriters Re |  | 4.1 |  |  | 9 | % |  | A
Transatlantic Reinsurance |  | 2.0 |  |  | 5 | % |  | A
1) A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings) and “A” (Excellent, which is the third highest of fifteen financial strength ratings).
Listing of Sirius's top reinsurers | The following table provides a listing of Sirius Group’s top reinsurers based upon recoverable amounts, the percentage of total paid and unpaid reinsurance recoverables and the reinsurers’ A.M. Best ratings.
Top Reinsurers (Millions) |  | Balance at September 30, 2012 |  | % of Total |  | A.M. Best Rating (1) |  | % Collateralized
General Reinsurance Corporation |  | $ | 42.3 |  |  | 13 | % |  | A++ |  | 1 | %
Swiss Re Group |  | 33.7 |  |  | 10 | % |  | A+ |  | 5 | %
Lloyds of London (2) |  | 29.9 |  |  | 9 | % |  | A |  | 4 | %
Olympus (3) |  | 28.8 |  |  | 9 | % |  | NR-5 |  | 100 | %
Michigan Catastrophic Claims Association (4) |  | 14.6 |  |  | 4 | % |  | N/A |  | — | %
(1) A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings), “A” (Excellent, which is the third highest of fifteen financial strength ratings) and “NR-5” (Not formally followed). (2) Represents the total of reinsurance recoverables due to Sirius Group from all Lloyds Syndicates. (3) Non-U.S. insurance entity. The balance is fully collateralized through funds held, letters of credit or trust agreements. (4) Michigan Catastrophic Claims Association ("MCCA") is a non-profit unincorporated association., established by the State of Michigan with the power to issue and collect assessments, to which every insurance company that sells automobile coverage in Michigan is required to be a member. A.M. Best does not rate MCCA. Sirius Group acquired its recoverable from MCCA in the acquisition of Stockbridge Insurance Company. As part of the acquisition, Sirius Group obtained $25.0 of reinsurance protection from the seller (currently rated A+ by A.M. Best) for unfavorable loss reserve development, including uncollectible reinsurance.

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- Definition Tabular disclosure of the top five reinsurers that have assumed business from OneBeacon (excluding industry pools and associations) based on the amount recoverable from each reinsurer. The disclosure for each reinsurer also includes the amount recoverable as a percentage of OneBeacon's consolidated reinsurance recoverables and the A.M Best Company, Inc. ("A.M. Best") rating. + References No definition available. + Details
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- Definition Tabular disclosure of the top five reinsurers that have assumed business from Sirius based on the amount recoverable from each reinsurer. The disclosure for each reinsurer also includes the amount recoverable as a percentage of Sirius's total reinsurance recoverables, the A.M Best Company, Inc. ("A.M. Best") rating and the percentage of the amount recoverable that is collateralized. + References No definition available. + Details
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