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Investment Securities - Investment Holdings (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021
U.S. Government and agency obligations |  |
Investment securities |  |
Cost or Amortized Cost | $ 216.6 | $ 212.1
Gross Unrealized Gains | 0.0 | 0.5
Gross Unrealized Losses | (10.2) | (1.1)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 206.4 | 211.5
Debt securities issued by corporations |  |
Investment securities |  |
Cost or Amortized Cost | 1,098.3 | 993.3
Gross Unrealized Gains | 0.6 | 8.7
Gross Unrealized Losses | (78.3) | (8.7)
Net Foreign Currency Gains (Losses) | (1.8) | (0.4)
Carrying Value | 1,018.8 | 992.9
Municipal obligations |  |
Investment securities |  |
Cost or Amortized Cost | 281.6 | 276.4
Gross Unrealized Gains | 0.4 | 16.8
Gross Unrealized Losses | (23.4) | (1.3)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 258.6 | 291.9
Mortgage and asset-backed securities |  |
Investment securities |  |
Cost or Amortized Cost | 288.7 | 277.2
Gross Unrealized Gains | 0.0 | 2.9
Gross Unrealized Losses | (34.5) | (2.5)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 254.2 | 277.6
Collateralized loan obligations |  |
Investment securities |  |
Cost or Amortized Cost | 190.8 | 136.5
Gross Unrealized Gains | 0.1 | 0.0
Gross Unrealized Losses | (6.0) | (0.4)
Net Foreign Currency Gains (Losses) | (2.0) | (1.1)
Carrying Value | 182.9 | 135.0
Total fixed maturity investments |  |
Investment securities |  |
Cost or Amortized Cost | 2,076.0 | 1,895.5
Gross Unrealized Gains | 1.1 | 28.9
Gross Unrealized Losses | (152.4) | (14.0)
Net Foreign Currency Gains (Losses) | (3.8) | (1.5)
Carrying Value | $ 1,920.9 | $ 1,908.9
Including short term fixed |  |
Investment securities |  |
Duration of fixed maturities (years) | 2 years 3 months 18 days |
Excluding short term investments |  |
Investment securities |  |
Duration of fixed maturities (years) | 3 years 4 months 24 days |

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