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Debt - Summary of Debt Obligations (Details) - USD ($) | Jun. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 917,900,000 | $ 1,146,700,000
Federal Home Loan Bank Advances (FHLB) |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 0 | 155,000,000.0
Stated interest rate | 1.91% |
Senior Notes | 5.75% Senior Notes Due 2023 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 241,600,000 | 241,300,000
Stated interest rate | 5.75% |
Debt instrument, face amount | $ 242,300,000 |
Senior Notes | 5.25% Senior Notes Due 2028 |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 641,000,000.0 | 640,200,000
Stated interest rate | 5.25% |
Debt instrument, face amount | $ 650,000,000 |
9% Convertible Junior Subordinated Debentures |  |
Debt Instrument [Line Items] |  |
Long-term debt, carrying value | $ 35,300,000 | $ 110,200,000
Stated interest rate | 9.00% |

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