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Investments in Unconsolidated Affiliates (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  |  |  |  |  | 12 Months Ended
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Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2012 Symetra | Dec. 31, 2011 Symetra | Dec. 31, 2010 Symetra | Dec. 31, 2009 Symetra | Dec. 31, 2012 Symetra Common shareholders’ equity | Dec. 31, 2011 Symetra Common shareholders’ equity | Dec. 31, 2010 Symetra Common shareholders’ equity | Dec. 31, 2009 Symetra Common shareholders’ equity | Dec. 31, 2012 Symetra Warrants | Dec. 31, 2011 Symetra Warrants | Dec. 31, 2010 Symetra Warrants | Dec. 31, 2009 Symetra Warrants | Dec. 31, 2012 Hamer, LLC | Dec. 31, 2011 Hamer, LLC | Dec. 31, 2012 Bri-Mar Manufacturing, LLC | Dec. 31, 2011 Bri-Mar Manufacturing, LLC | Dec. 31, 2012 Pentelia Capital Management | Dec. 31, 2011 Pentelia Capital Management | Dec. 31, 2010 Pentelia Capital Management
Investments in unconsolidated affiliates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity in earnings (losses) of unconsolidated affiliates | $ 5.5 | $ 7.7 | $ 6.5 | $ 10.2 | $ (36.4) | $ 1.5 | $ 7.9 | $ 6.8 | $ 29.9 | $ (20.2) | $ 9.9 | $ 32.3 | [1],[2],[3] | $ 28.2 | [1],[2] | $ 11.1 | [1],[2],[4] |  |  | $ 32.3 | [1],[2],[3] | $ 28.2 | [1],[2] | $ 11.1 | [1],[2],[4] |  |  | $ 0 | [1],[2],[3] | $ 0 | [1],[2] | $ 0 | [1],[2],[4] |  |  |  |  |  |  |  |  |  |  | $ (1.3) | $ (0.2) | $ 0.5
Symetra common shares |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 288.4 |  | 261.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unrealized gains from Symetra’s fixed maturity portfolio |  |  |  |  |  |  |  |  |  |  |  | 62.8 |  | 0 |  | 63.7 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total investment in Symetra | $ 387.9 |  |  |  | $ 275.3 |  |  |  | $ 387.9 | $ 275.3 |  | $ 381.5 | [5],[6] | $ 273.6 | [5] | $ 387.5 | [5] | $ 307.7 | [5] | $ 351.2 | [5],[6] | $ 261.0 | [5] | $ 350.4 | [5] | $ 269.2 | [5] | $ 30.3 | [5],[6] | $ 12.6 | [5] | $ 37.1 | [5] | $ 38.5 | [5] | $ 4.0 | [7] | $ 0 | [7] | $ 1.9 | [7] | $ 0 | [7] | $ 0.5 | $ 1.7 |
[1] | Equity in earnings for the years end December 31, 2012, 2011 and 2010 includes $1.3, $1.0, and $0.8 loss from the dilutive effect of Symetra’s yearly dividend and the issuance of restricted shares by Symetra
[2] | Equity in earnings for the years end December 31, 2012, 2011 and 2010 excludes tax expense of $2.6, $2.3, and $1.4
[3] | Equity in earnings includes $3.5 increase relating to the pre-tax amortization of Symetra common share impairment from December 31, 2012.
[4] | Includes a $17.9 loss from the dilutive effect of Symetra’s public offering
[5] | Includes White Mountains’ equity in net unrealized gains (losses) from Symetra’s fixed maturity portfolio of $62.8, $0, and $63.7 as of December 31, 2012, 2011 and 2010, which excludes tax expense of $5.1, $0 and $5.2
[6] | The aggregate value of White Mountains’ investment in common shares of Symetra was $225.9 based upon the quoted market price of $12.98 per share at December 31, 2012.
[7] | As of October 1, 2012, Hamer and Bri-Mar are no longer consolidated and are accounted for as investments in unconsolidated affiliates.

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