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Investment Securities - Investment Holdings Fixed Maturity Table (Details) - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021
--- | --- | ---
U.S. Government and agency obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | $ 181.4 | $ 212.1
Gross Unrealized Gains | 0.0 | 0.5
Gross Unrealized Losses | (5.3) | (1.1)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 176.1 | 211.5
Debt securities issued by corporations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | 1,013.4 | 993.3
Gross Unrealized Gains | 1.4 | 8.7
Gross Unrealized Losses | (45.4) | (8.7)
Net Foreign Currency Gains (Losses) | 0.2 | (0.4)
Carrying Value | 969.6 | 992.9
Municipal obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | 272.2 | 276.4
Gross Unrealized Gains | 6.0 | 16.8
Gross Unrealized Losses | (5.9) | (1.3)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 272.3 | 291.9
Mortgage and asset-backed securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | 278.2 | 277.2
Gross Unrealized Gains | 0.2 | 2.9
Gross Unrealized Losses | (14.3) | (2.5)
Net Foreign Currency Gains (Losses) | 0.0 | 0.0
Carrying Value | 264.1 | 277.6
Collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | 136.5 | 136.5
Gross Unrealized Gains | 0.0 | 0.0
Gross Unrealized Losses | (1.6) | (0.4)
Net Foreign Currency Gains (Losses) | (1.5) | (1.1)
Carrying Value | 133.4 | 135.0
Total fixed maturity investments |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Cost or Amortized Cost | 1,881.7 | 1,895.5
Gross Unrealized Gains | 7.6 | 28.9
Gross Unrealized Losses | (72.5) | (14.0)
Net Foreign Currency Gains (Losses) | (1.3) | (1.5)
Carrying Value | $ 1,815.5 | $ 1,908.9

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