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Debt - Summary of Obligations (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 662.8 | $ 1,146.7
Federal Home Loan Bank Advances (FHLB) |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | 0.0 | $ 155.0
FHLBC fixed interest rate |  | 1.91%
Senior Notes | 5.75% Senior Notes due 2023 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | 0.0 | $ 241.3
Senior Notes | 5.25% Senior Notes due 2028 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | 641.7 | 640.2
Convertible Junior Subordinated Debentures, at 9% per annum, Due 2063 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 21.1 | $ 110.2

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