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Investment Securities (Net Realized and Unrealized Gains (Losses) After Tax) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Investments in and Advances to Affiliates [Line Items] |  |  |
Net change in pre-tax unrealized investment (losses) gains on investments in unconsolidated affiliates | $ 0.0 | $ (39.2) | $ 81.2
Income tax benefit (expense) | 0.0 | 2.9 | (5.9)
Net change in unrealized investment (losses) gains on investments in unconsolidated affiliates, after tax | 0.0 | (36.3) | 75.3
Net change in unrealized investment (losses) gains on investments in unconsolidated affiliates, after tax | 0.0 | (34.9) | 75.3
Net Realized and Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax | 1.5 | 190.2 | 60.5
Total investment gains recorded during the period, after-tax | 1.5 | 155.3 | 135.8
Symetra |  |  |
Investments in and Advances to Affiliates [Line Items] |  |  |
Net change in unrealized investment (losses) gains on investments in unconsolidated affiliates, after tax | 0.0 | (34.9) | 75.3
Reversal of accumulated other comprehensive income related to change in accounting for the investment in Symetra | $ 0.0 | $ 1.4 | $ 0.0

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- Definition The net unrealized gains (losses) from Symetra's fixed maturity portfolio. + References No definition available. + Details
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- Definition Represents recognized after tax amortization through equity in net unrealized losses from investments in unconsolidated affiliates. + References No definition available. + Details
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- Definition Net Realized and Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax + References No definition available. + Details
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- Definition Other Comprehensive Income, Reversal of accumulated other comprehensive income, Unrealized Gain (Loss) on Investments, Net of Tax Period Increase (Decrease) + References No definition available. + Details
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