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v3.20.4

Debt (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Aug. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) Period $ / shares shares | Sep. 30, 2020 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) Period $ / shares shares | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Early repayment of debt |  |  |  |  |  | $ 179,735,000 | $ 0 | $ 0
Loss on debt extinguishment |  | $ 0 | $ 26,736,000 | $ 0 | $ 0 | 26,736,000 | 0 | 0
FHLBC advances |  | $ 155,000,000.0 |  |  |  | $ 155,000,000.0 |  |
FHLBC fixed interest rate |  | 1.91% |  |  |  | 1.91% |  |
Collateral pledged to principal balance of FHLB advance (as a percent) |  |  |  |  |  | 102.00% |  |
Interest paid |  |  |  |  |  | $ 54,300,000 | $ 50,800,000 | $ 51,300,000
Senior Notes | 5.75% Senior Notes due 2023 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Stated interest rate (in hundredths) |  | 5.75% |  |  |  | 5.75% |  |
Debt instrument, face amount |  | $ 242,300,000 |  |  |  | $ 242,300,000 |  |
Extinguishment of debt |  |  |  |  |  | 182,700,000 |  |
Early repayment of debt |  |  |  |  |  | 197,800,000 |  |
Loss on debt extinguishment |  |  |  |  |  | $ 16,500,000 |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 100.00% |  |
Ownership percentage threshold for declaration of due and payable |  |  |  |  |  | 25.00% |  |
Senior Notes | 5.25% Senior Notes due 2028 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Stated interest rate (in hundredths) | 5.25% | 5.25% |  |  |  | 5.25% |  |
Debt instrument, face amount | $ 650,000,000 | $ 650,000,000 |  |  |  | $ 650,000,000 |  |
Proceeds from issuance of debt | 640,300,000 |  |  |  |  |  |  |
Debt issuance costs | $ 2,000,000.0 |  |  |  |  |  |  |
Ownership percentage threshold for declaration of due and payable |  |  |  |  |  | 25.00% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period One |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 102.625% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period Two |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 102.625% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period Two | US Treasury (UST) Interest Rate |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  |  | 0.50% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period Three |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 102.625% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period Four |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 101.313% |  |
Senior Notes | 5.25% Senior Notes due 2028 | Debt Instrument, Redemption, Period Five |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 100.00% |  |
Convertible Junior Subordinated Debentures, at 9% per annum, Due 2063 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Stated interest rate (in hundredths) |  | 9.00% |  |  |  | 9.00% |  |
Extinguishment of debt |  |  |  |  |  | $ 48,100,000 |  |
Loss on debt extinguishment |  |  |  |  |  | 10,200,000 |  |
Repayments of long-term debt |  |  |  |  |  | 61,600,000 |  |
Reacquisition of convertible junior subordinated debentures-equity component |  |  |  |  |  | $ 2,700,000 |  |
Reduction in potentially dilutive shares due to debt extinguishment | shares |  |  |  |  |  | 3,600,000 |  |
Redemption price, percentage (in hundredths) |  |  |  |  |  | 100.00% |  |
Conversion price (in dollars per share) | $ / shares |  | $ 13.23 |  |  |  | $ 13.23 |  |
Conversion rate (in shares per $1,000 note) | shares |  |  |  |  |  | 75.5932 |  |
Principal amount of notes used in determining conversion rate |  | $ 1,000 |  |  |  | $ 1,000 |  |
Period preceding election to convert |  |  |  |  |  | 5 days |  |
Closing sale price of our common stock for consideration of redemption (in dollars per share) | $ / shares |  | $ 17.20 |  |  |  | $ 17.20 |  |
Minimum number of trading days |  |  |  |  |  | 20 days |  |
Maximum number of trading days |  |  |  |  |  | 30 days |  |
Minimum number of consecutive interest periods for which interest payments may be deferred | Period |  | 1 |  |  |  | 1 |  |
Maximum period for which interest payments may be deferred without giving rise to an event of default |  |  |  |  |  | 10 years |  |
Period in which reasonable commercial efforts must begin, maximum |  |  |  |  |  | 1 day |  |
Anniversary payment release of the start of the interest deferral to the Alternative Payment Mechanism in lieu of the final maturity of the debentures |  |  |  |  |  | 10 years |  |
Net proceeds cap (in hundredths) |  | 2.00% |  |  |  | 2.00% |  |
Maximum number of shares of common stock issuable under the Alternative Payment Mechanism (in shares) | shares |  | 10,000,000 |  |  |  | 10,000,000 |  |
Maximum percentage of aggregate principal amount of the debentures (in hundredths) |  | 25.00% |  |  |  | 25.00% |  |

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