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Debt Summary of Obligations (Details) - USD ($) | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 832,700,000 | $ 831,600,000
Federal Home Loan Bank Advances (FHLB) |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | 155,000,000.0 | 155,000,000.0
Senior Notes | 5.75% Senior Notes due 2023 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 420,900,000 | 419,700,000
Stated interest rate (in hundredths) | 5.75% |
Debt instrument, face amount | $ 425,000,000 |
Convertible Junior Subordinated Debentures, at 9% per annum, Due 2063 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 256,900,000 | $ 256,900,000
Stated interest rate (in hundredths) | 9.00% |

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