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Investments in Unconsolidated Affiliates (Tables) | 9 Months Ended
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Sep. 30, 2016
Equity Method Investments and Joint Ventures [Abstract] |
Schedule of Changes in Investments in Unconsolidated Affiliates | The following table summarizes amounts recorded by White Mountains under the equity method relating to its investment in Symetra for the three and nine months ended September 30, 2015:
|  | Three Months Ended |  | Nine Months Ended
Millions |  | September 30, 2015 |  | September 30, 2015
Equity method carrying value of investment in Symetra at the beginning of the period |  | $ | 397.2 |  |  | $ | 411.4 |
Equity in earnings (1)(2) |  | 4.2 |  |  | 17.5 |
Equity in net unrealized gains (losses) from Symetra’s fixed maturity portfolio (3) |  | 3.7 |  |  | (31.8 | )
Dividends received |  | (12.5 | ) |  | (16.9 | )
Distribution from Prospector Offshore Fund |  | — |  |  | 12.4 |
Equity method carrying value of investment in Symetra at the end of the period(4) |  | $ | 392.6 |  |  | $ | 392.6 |
(1) For the three and nine months ended September 30, 2015, equity in earnings excludes tax expense of $0.3 and $1.1. (2) For the three and nine months ended September 30, 2015, equity in earnings includes $0.7 and $2.1 increase relating to the pre-tax amortization of the Symetra common share basis difference. (3) For the three and nine months ended September 30, 2015, net unrealized gains includes $2.9 and $8.6 increase relating to the pre-tax amortization of the Symetra common share basis difference. (4) Includes White Mountains’s equity in net unrealized gains from Symetra’s fixed maturity portfolio of $5.7 as of September 30, 2015, which excludes tax expense of $0.2.

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