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Investments in Unconsolidated Affiliates (Investments in Symetra Table Rollforward) (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Jun. 30, 2015 | Jun. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Carrying value at the beginning of the period |  |  | $ 414.4 |  | $ 414.4 |
Equity in earnings | $ 3.9 | $ 7.0 |  |  | 18.0 | $ 33.3
Carrying value at the end of the period | 392.6 |  |  |  | 392.6 |
Income Tax Expense (Benefit) | $ (1.6) | (4.7) |  |  | $ 0.8 | 11.4
Symetra | Common Stock |  |  |  |  |  |
Investments in unconsolidated affiliates |  |  |  |  |  |
Share Price | $ 31.64 |  |  |  | $ 31.64 |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Carrying value at the beginning of the period | $ 397.2 | 415.5 | 411.4 | $ 317.3 | $ 411.4 | 317.3
Equity in earnings | 4.2 | 7.0 |  |  | 17.5 | 34.5
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio | 3.7 | (10.7) |  |  | (31.8) | 64.0
Dividends received | (12.5) | (2.0) |  |  | (16.9) | (6.0)
Carrying value at the end of the period | 392.6 | 409.8 | $ 397.2 | $ 415.5 | 392.6 | 409.8
Aggregate value of White Mountains common shares of Symetra at quoted market price | 650.6 |  |  |  | 650.6 |
Number of Shares Distributed | 0.0 | 0.0 |  |  | 12.4 | 0.0
White Mountains | Common Stock |  |  |  |  |  |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio |  |  |  |  | 5.7 | 20.5
equity in earnings of unconsolidated affiliates | Symetra | Common Stock |  |  |  |  |  |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Income Tax Expense (Benefit) | 0.3 | 0.5 |  |  | 1.1 | 2.4
Net unrealized gains (losses) of unconsolidated affiliates | White Mountains | Common Stock |  |  |  |  |  |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Income Tax Expense (Benefit) |  |  |  |  | 0.2 | 1.4
Amortization of common share basis difference | Symetra | Common Stock |  |  |  |  |  |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Equity in earnings | 0.7 | 0.7 |  |  | 2.1 | 2.2
impairment of net unrealized gains (losses) | Net unrealized gains (losses) of unconsolidated affiliates | Symetra | Common Stock |  |  |  |  |  |
Changes in carrying value of investment in Symetra |  |  |  |  |  |
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio | $ 2.9 | $ 3.1 |  |  | $ 8.6 | $ 9.4

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