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Investment Securities (Investment gains (losses) for Level 3) (Details) (Level 3 Inputs, USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012
Investment securities |  |  |  |
Unrealized gains (losses) on investments | $ 1.8 | $ 2.2 | $ 8.3 | $ 17.7
Fixed maturity investments. |  |  |  |
Investment securities |  |  |  |
Unrealized gains (losses) on investments | (0.4) | 0.5 | (0.2) | 8.3
Common equity securities |  |  |  |
Investment securities |  |  |  |
Unrealized gains (losses) on investments | 0.8 | 0.5 | 0.7 | 1.0
Other long-term investments |  |  |  |
Investment securities |  |  |  |
Unrealized gains (losses) on investments | $ 1.4 | $ 1.2 | $ 7.8 | $ 8.4

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- Definition The aggregate increase (decrease) in the market value of unsold investments whose gains (losses) are included in earnings. + References No definition available. + Details
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