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Investment Securities - Investment Holdings (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020
U.S. Government and agency obligations |  |
Investment securities |  |
Cost or Amortized Cost | $ 212.1 | $ 173.2
Gross Unrealized Gains | 0.5 | 3.1
Gross Unrealized Losses | (1.1) | 0.0
Net Foreign Currency Gains (Losses) | 0.0 |
Carrying Value | 211.5 | 176.3
Debt securities issued by corporations |  |
Investment securities |  |
Cost or Amortized Cost | 993.3 | 522.8
Gross Unrealized Gains | 8.7 | 24.7
Gross Unrealized Losses | (8.7) | (0.1)
Net Foreign Currency Gains (Losses) | (0.4) |
Carrying Value | 992.9 | 547.4
Municipal obligations |  |
Investment securities |  |
Cost or Amortized Cost | 276.4 | 244.0
Gross Unrealized Gains | 16.8 | 21.0
Gross Unrealized Losses | (1.3) | 0.0
Net Foreign Currency Gains (Losses) | 0.0 |
Carrying Value | 291.9 | 265.0
Mortgage and asset-backed securities |  |
Investment securities |  |
Cost or Amortized Cost | 277.2 | 211.7
Gross Unrealized Gains | 2.9 | 6.8
Gross Unrealized Losses | (2.5) | 0.0
Net Foreign Currency Gains (Losses) | 0.0 |
Carrying Value | 277.6 | 218.5
Collateralized loan obligations |  |
Investment securities |  |
Cost or Amortized Cost | 136.5 |
Gross Unrealized Gains | 0.0 |
Gross Unrealized Losses | (0.4) |
Net Foreign Currency Gains (Losses) | (1.1) |
Carrying Value | 135.0 |
Total fixed maturity investments |  |
Investment securities |  |
Cost or Amortized Cost | 1,895.5 | 1,151.7
Gross Unrealized Gains | 28.9 | 55.6
Gross Unrealized Losses | (14.0) | (0.1)
Net Foreign Currency Gains (Losses) | (1.5) |
Carrying Value | $ 1,908.9 | $ 1,207.2
Including short term fixed |  |
Investment securities |  |
Duration of fixed maturities (years) | 2 years 7 months 6 days |
Excluding short term investments |  |
Investment securities |  |
Duration of fixed maturities (years) | 3 years 2 months 12 days |

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