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Investment Securities (Investment Holdings) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Investment securities |  |  |
Fixed maturity investments, at fair value | $ 4,250.2 | $ 2,630.2 |
Including Short Term Fixed |  |  |
Investment securities |  |  |
Duration of Fixed Maturities | 2 years 9 months 18 days |  |
US Government and agency obligations |  |  |
Investment securities |  |  |
Trading Securities, Cost | $ 281.7 | 160.4 |
Net foreign currency gains | 0.0 | 0.0 |
Fixed maturity investments, at fair value | 278.3 | 160.0 |
Trading Securities, Unrealized Holding Gain | 0.1 | 0.0 |
Trading Securities, Unrealized Holding Loss | (3.5) | (0.4) |
Debt securities issued by corporations |  |  |
Investment securities |  |  |
Trading Securities, Cost | 1,512.6 | 1,001.0 |
Net foreign currency gains | 2.1 | 0.0 |
Fixed maturity investments, at fair value | 1,509.4 | 1,000.0 |
Trading Securities, Unrealized Holding Gain | 8.4 | 4.3 |
Trading Securities, Unrealized Holding Loss | (13.7) | (5.3) |
Municipal obligations |  |  |
Investment securities |  |  |
Trading Securities, Cost | 308.8 | 227.8 |
Net foreign currency gains | 0.0 | 0.0 |
Fixed maturity investments, at fair value | 309.0 | 228.8 |
Trading Securities, Unrealized Holding Gain | 1.9 | 2.2 |
Trading Securities, Unrealized Holding Loss | (1.7) | (1.2) |
Mortgage and asset-backed securities |  |  |
Investment securities |  |  |
Trading Securities, Cost | 2,141.7 | 1,170.6 |
Net foreign currency gains | 0.0 | 0.0 |
Fixed maturity investments, at fair value | 2,132.9 | 1,167.0 |
Trading Securities, Unrealized Holding Gain | 2.6 | 2.0 |
Trading Securities, Unrealized Holding Loss | (11.4) | (5.6) |
Foreign government, agency and provincial obligations |  |  |
Investment securities |  |  |
Trading Securities, Cost | 12.9 | 1.0 |
Net foreign currency gains | 0.0 | 0.0 |
Fixed maturity investments, at fair value | 13.2 | 1.2 |
Trading Securities, Unrealized Holding Gain | 0.3 | 0.2 |
Trading Securities, Unrealized Holding Loss | 0.0 | 0.0 |
Preferred stocks |  |  |
Investment securities |  |  |
Trading Securities, Cost | 8.3 | 78.3 |
Net foreign currency gains | 0.0 | 0.0 |
Fixed maturity investments, at fair value | 14.0 | 82.7 |
Trading Securities, Unrealized Holding Gain | 5.7 | 4.4 |
Trading Securities, Unrealized Holding Loss | 0.0 | 0.0 |
Fixed Income Investments [Member] |  |  |
Investment securities |  |  |
Trading Securities, Cost | 4,266.0 | 2,639.1 |
Net foreign currency gains | 2.1 | 0.0 |
Total fixed maturity investments | 4,256.8 | 2,639.7 |
Trading Securities, Unrealized Holding Gain | 19.0 | 13.1 |
Trading Securities, Unrealized Holding Loss | $ (30.3) | (12.5) |
Excluding Short Term Investments |  |  |
Investment securities |  |  |
Duration of Fixed Maturities | 3 years |  |
Star & Shield Insurance Exchange [Member] |  |  |
Investment securities |  |  |
Fixed maturity investments reclassified to assets held for sale (1) | $ (6.6) | (9.5) |
Fixed maturity investments | Star & Shield Insurance Exchange [Member] |  |  |
Investment securities |  |  |
Fixed maturity investments, at fair value | $ 6.6 | $ 9.5 | $ 10.1

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